INVESTIGATION NUMBER 615 FINAL REPORT

MAY 1971

-.,:_ TECHNICAL BULLETIN 282 AGRICULTURAL EXPERIMENT STATION

DEVELOPMENT OF GROUND COVERS

FOR HIGHWAY SLOPES

Development of Ground Covers for Highway Slopes

FINAL REPORT-1971

Investigation No. 615

Albert G. Johnson, Donald B. White, Margaret H. Smithberg, and Leon C. Snyder•

Department of Horticultural Science, University of Minnesota in cooperation with

U.S. Department of Transportation, Federal Highway Administration Minnesota Highway Department

Minnesota Local Road Research Board

The opinions, findings, and conclusions expressed in this publication are those of the Department of Horticultural Science, University of Minnesota and not necessarily those of the Federal Highway Administration.

* Authors are University of Minnesota personnel:

Albert G. Johnson is research associate, University of Minnesota Landscape Arboretum

Donald B. White is professor, Horticultural Science Margaret H. Smithberg is associate scientist, Horticultural Science Leon C. Snyder is director, University of Minnesota Landscape Arboretum

Table of Contents Page

I. Evaluation Categories . . . . . . . . . . . . . . . . . . . . . . . . . 8

II. Evaluation of Plant Materials Evaluation of Plant Materials and Hardiness 29 University of Minnesota Landscape Arboretum Evaluations

Plant Introduction Nursery . . . . . . . . . . . . . . . . . . . 30 Arboretum South Bank Planting . . . . . . . . . . . . . . 30 Arboretum Service Area Bank Planting . . . . . . . . . 30 Arboretum Roadside Planting-1966 .......... 30 Nursery for Plants of Sandy Acid Soils . . . . . . . . 31

University of Minnesota Branch Experiment Station Evaluations

Grand Rapids Loon Lake Plantings . . . . . . . . . . . . . . . . . . . . . . 31 Wendigo Slope-Community Park Plantings-1965 ......................... 32

Morris Station-1967 ....................... 33

Crookston Station-1965 .................... 33

Highway Site Evaluations

1-494 Plantings-1963 ...................... 33 TH-65 Plantings-Soderville, Anoka County . . . . 36 Cleveland Avenue, Roseville, Ramsey County, Dwarf Southernwood Plantings . . . . . . . . . . . . . . . 36 Lakeville 1-35 Plantings-1967 ............... 36

Native Ground Cover Collections ............... 38

Experiments in Propagation and Establishment Crownvetch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Direct Seeding of Woody Plants

Smooth Sumac . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Direct Seeding of Smooth Sumac . . . . . . . . . . . . 42 Hydroseeding of Smooth Sumac Seed . . . . . . . . 42 Direct Seeding of Woody Ground Covers-Cannon Falls . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Plant Surveys of Existing Highway Slopes . . . . . . . . . 43

Additional Research Considerations . . . . . . . . . . . . . . 43

Miscellaneous Small Trees Brought into the Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

III. Establishment and Maintenance of Plant Materials

Grades and Standards . . . . . . . . . . . . . . . . . . . . . . . . . 44 Source of Plant Materials . . . . . . . . . . . . . . . . . . . . . . 44 Handling of Plant Materials . . . . . . . . . . . . . . . . . . . . 44 Planting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

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Page

Planting of Nursery Stock . . . . . . . . . . . . . . . . . . . . . . 44 Establishment of Plant Materials . . . . . . . . . . . . . . . . 45 Maintenance of Plant Materials . . . . . . . . . . . . . . . . . 45 Availability of Plant Materials .................. 45

Tables 1. Ground covers recommended for use on

highway slopes in Minnesota . . . . . . . . . . . . . . . . . . . . 8 2. Plants recommended for limited use on

Minnesota roadsides . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3. Plants not recommended or not sufficiently

evaluated for Minnesota roadsides . . . . . . . . . . . . . . . 18 4. Arboretum bank planting-1963 ................. 30 5. Evaluation of plants in arboretum service area in

1964 and 1969 (planted with potted stock August 9, 1963) .............................. 31

6. Relative performance ratings of ground covers after one and three seasons on the Landscape Arboretum roadside (planted 1966, rated 1967 and 1969) ..... 31

7. 1969 evaluation-Loon Lake plantings (planted 1964 and 1965) ................................... 32

8. Iron chlorosis on potential ground cover plants grown at Crookston, Minnesota, 1967 ............ 33

9. Evaluation of plantings, 1-494, planted 1963, 1964, 1965, and 1966 .............................. 34

10. 1969 evaluation of materials planted in 1963 and 1964 on TH-65 ............................... 37

11. Performance of selected junipers after 2 years on the Lakeville site: planted 1967 ............... 38

12. Germination and ground cover evaluation of herbaceous materials: planted 1967 at Lakeville .... 38

13. Performance of deciduous shrub plantings: planted 1967 at Lakeville ............................. 38

14. Rating of Creeping Juniper collected from native stands after 2 years of growth: planted 1963 ...... 39

15. Mean ratings for establishment of transplanted seed­lings of four Crownvetch varieties: planted May 25, 1967, and rated July 23, 1968 .................. 40

16. Mean heights and widths of four varieties of Crown­vetch after one growing season from seed: planted June 1, 1964, scored October 7, 1964 ............ 41

17. Ratings of Crownvetch seedlings grown on the Land­scape Arboretum slope: planted April 28, 1964, scored September 11, 1966 ..................... 41

18. Mean heights and widths of five Crownvetch varieties grown from seedlings: planted May 9, 1967, scored July 23, 1968 .......................... 41

19. Cannon Falls direct seeding test: plant and mulch materials used ................................ 42

20. Evaluation of small trees for roadside planting . . . . . 43

Figures Page

1. Zones of plant hardiness in _Mi~nesota from the USDA Miscellaneous Publication No. 814, 1960 .... 7

2. Bearberry ........................... · · · · · · · · 46 3. Crownvetch ................................ · · 46 4. Tawny Daylily . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

5. Redosier Dogwood ............................ 46

6. Arcadia Juniper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

7. Skandia Juniper .................. · · · · · · · · · · · · 46 8. Creeping Juniper ............................. 47

9. Japanese Garden Juniper ....................... 47

10. Oldfield or Prostrate Juniper . . . . . . . . . . . . . . . . . . . . 47 11. Pfitzer Juniper ............................... 47 12. Sargent Juniper .............................. 47 13. Cicer Milkvetch .............................. 47

14. Kamchatka Rose ............................. 48 15. Fragrant Sumac .............................. 48

16. Smooth Sumac . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

17. Birdsfoot Trefoil .............................. 48 18. Prostrate Alfalfa . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

19. Pirone Alfalfa ................................ 48

20. Sicklepod Alfalfa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

21. Barrenstrawberry ............................. 49

22. Bayberry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

23. Allegheny Blackberry .......................... 49

24. Georgia Bushhoneysuckle . . . . . . . . . . . . . . . . . . . . . . 49

25. Dwarf Spring Cinquefoil ....................... 49

26. Wineleaf Cinquefoil . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

27. Friedrichseni Cinquefoil . . . . . . . . . . . . . . . . . . . . . . . 50

28. Irving Cinquefoil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

29. White Clover ................................ 50

30. Zigzag Clover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

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Figures Page

31. Cowberry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 32. Thicket Creeper .............................. 51

33. Virginia Creeper .............................. 51

34. Reynoutria Fleeceflower ....................... 51 35. Lilac Honeysuckle ............................ 51

36. Rush Lespedeza .............................. 51

37. Sicklepod Milkvetch .......................... · 51 38. India Mockstrawberry . . . . . . . . . . . . . . . . . . . . . . . . . 52

39. Partridgepea ................................ . 52

40. Russian Peashrub . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

41. Perennial Peavine ............................. 52

42. Herbaceous Periwinkle . . . . . . . . . . . . . . . . . . . . . . . . . 52

43. Quicksilver Petunia ........................ · · · 52

44. Alaska Phlox ............................ · · · · 53

45. Maiden Pink ............................ · · · · · 53

46.

47.

Magic Carpet Polygonum ................ · · · · · ·

Japanese Trailing Raspberry ............. · · · · · · ·

48. Fringed Sage .................. · · · · · · · · · · · · · · ·

53 53

53

49. Common Snowberry ....................... · · · · 53

50. Dwarf Southernwood ...................... · · · · 54

51. Billiard Spirea ................. · · · · · · · · · · · · · · · 54

52. Dwarf Garland Spirea .................... · · · · · 54

53. Dwarf Cutleaf Stephanandra ............... · · · · · 54

54. Two-row Stonecrop ................ · · · · · · · · · · · 54

55. Sweetfern ..................... · · · · · · · · · · · · · · 54

56. Bird Vetch ................... · · · · · · · · · · · 55 55 57. Virginsbower .................. · · · · · · · · · · · · · · 55 58. Wolfberry ....................... · · · · · · · · · · · ·

59. Adamsneedle Yucca .............. · · · · · · · · · · · · · 55

60. 1963 plants on 1-494 in Eden Prairie Township !! 61. Crownvetch plantings in Landscape Arboretum · · · ·

FOREWORD This report completes and organizes the research informa­

tion generated under Investigation 615: "Development of Ground Covers for Highway Slopes." It was written specifically for highway personnel and citizens who may be interested or in­volved in establishing ground covers in difficult situations. The report's main purpose is to summarize findings and de­velop recommendations from the project research.

The report is presented in three sections. Section One pre­sents recommendations resulting from the research. Section Two develops the research effort and results of investigations. Section Three is devoted to general cultural information and maintenance specifications that should be useful to field per­sonnel and administrators who are directly or indirectly in­vC1lved with highway maintenance situations.

For purposes of this report, ground covers are defined as plant materials, other than turfgrass, capable of providing a uniform dense covering over the soil surface and with a root system of sufficient density and depth to stabilize the soil on which they are planted. In investigations reported here, special emphasis has been placed on materials with a full growth height of 2 feet or less. However, certain materials that offer particularly valuable characteristics but did not fulfill this spe­cification were also considered.

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ACKNOWLEDGMENTS

Credit is due the following cooperating agencies involved in supporting and maintaining continued interest in the proj­ect: The Minnesota Highway Department, Minnesota Local Road Research Board, and the U.S. Department of Transpor­tation, Federal Highway Administration.

The original interest and efforts of J.H. Swanberg, former Deputy Commissioner; H.E. Olson, former Engineer of Road­side Development; and P.O. Velz, then Research Engineer, Minnesota Highway Department, deserve recognition.

The continued interest of C.K. Preus, Research Coordina­tion Engineer; F.C. Fredrickson, Materials Engineer; P.A. Jensen, former Research Engineer; P.J. Diethelm, Research Engineer; W.N. Yoerg, Research Operations Engineer; and B.F. Himmelman, Office Engineer, Minnesota Highway De­partment, in all aspects of the project is gratefully acknowl­edged. Special thanks are due Dr. L.E. Foote, Director of En­vironmental Services, Minnesota Highway Department, for his interest and help in many of the problems that inevitably arise in such an undertaking.

The Soil Conservation Service and the Plant Introduction Stations of the U.S. Department of Agriculture (USDA), ar­boretums, other institutions, and many interested individuals contributed greatly to the success of the project through their generosity with plant materials.

INTRODUCTION

This final report of Investigation 615, "Development of Ground Covers for Highway Slopes" has been prepared to summarize findings and results of investigations on the use of ground cover type plants for Minnesota roadsides. The in­vestigation was initiated at the request of the Minnesota High­way Department in July 1962. The research program was conducted by the Department of Horticultural Science, Agri­cultural Experiment Station, University of Minnesota for the Minnesota Highway Department, Minnesota Local Road Re­search Board, and the U.S. Department of Transportation, Federal Highway Administration.

The study was initiated only after it was determined there was insufficient information on ground cover plants and their use to develop recommendations for highway situations. The primary purpose of the investigations was to develop materials that would enhance safety and beauty, increase the effec­tiveness of erosion control, and reduce maintenance costs on Minnesota highways.

The objectives of the investigation follow: 1. Obtain, develop, and evaluate ground covers for Min­

nesota highway roadsides. 2. Survey, collect, and test native plant species potentially

useful as ground covers; study their ecological requirements and determine their applicability to highway slope planting.

~- Study t_he problems of slope planting in the field, in­cludmg estabhshment and maintenance.

4. S!udy. the cultu:e, propagation, hardiness, longevity, and ava1lab1hty of species recommended for slope planting.

SUMMARY Purpose

The purpose of the investigation was to research the cul­ture, h~rdi~~ss, longevity, propagation, maintenance, and gen­e~al smtab1hty of plant materials for use as ground covers on highway slopes in Minnesota.

Procedures The study w_as initiated in 1 ?62. During the next 6 years

over ~00 a~cess10ns ot plant_s w1~h ground covering potential were mvest1,?ated at the Umv~rs1ty of Minnesota Landscape Arboretum. · ~!ants were ac~mred from the nursery industry, foreign. countnes, USDA S01I Conservation Service, Plant Jn­troduct!on ~tat1ons, and by collection from the wild. Initial evalu~tion mcluded hardiness, habit of growth, propagation establishment, and cultural limitations. '

_The materials were also evaluated at University branch ex­penment stations in M_orris: Crookston, and Grand Rapids, and on selected roadside s!tes. Plantings were designed to evalu~te metho_ds of establishment and maintenance under roadside cond1t10ns.

* For brevity, often referred to later in text as Landscape Arboretum.

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Results Thirty-four vanetJes are recommended for use on Min­

nesota highway slopes. An additional 71 varieties are recom­mended for limited use or experimental planting for further evaluation.

Most leguminous species investigated established ~eadily from seed. Seedings of Milkvetch and Birdsfoot Trefoil re­sulted in excellent cover the first year from seeding. Crown­vetch, however, took two to several years to become estab­lished from seed, or one season from transplants.

Evergreen ground covers (junipers) established well using balled and burlapped or container grown stock 2-3 years old. Liners ( one year rooted cuttings) proved unsatisfactory under the limited cultural conditions on highway sites. Direct seed­ing of woody ground covers did not yield satisfactory results.

Conclusions and Recommendations 1. It was concluded that use of selected ground cover

plants may be a practical alternative to grass on bridge abut­ments, in certain urban situations, and on steep highway slopes under strict maintenance regimes.

2. It is recommended that provision be made to ensure further evaluation of plant materials listed in the limited use category and noted in table 3 as needing more study.

3. It is also evident that additional research is needed in the areas of salt tolerance and establishment and maintenance of native ground covers.

HARDINESS ZONE MAPS

Each species in this report has been designated with a hardiness rating that corresponds to the map developed by the USDA ( 1960) and refined for Minnesota (figure 1).

In this report Minnesota is divided into three hardiness zones. Plants are hardy in the zone designated and any zone with a higher number.

Occasionally very local situations ( conditions approximat­ing a milder climate) may exist where plants may survive in colder zones. The only way to ascertain these situations is by trial and error or detailed study. Plants can be recommended for use in colder than normal zones only in extraordinary situations.

SALT TOLERANCE

The use of salt for ice and snow removal on highways leads to injury to roadside vegetation. Plant species vary in their ability to tolerate salts in various concentrations. Selec­tion and use of salt tolerant plants in vulnerable situations of­fers a partial solution to the problem.

Comparatively little information is available concerning the salt tolerance of most of the ground cover plants covered in this report. No research on this aspect of the use of gro~nd cover plants was conducted in connection with Investigat10n

\

4

Ol'HO•"'ATCUOIG[Of OY[UGI UMYAL ll1H,10W

n11-i:u1~~[$ '°" UG" fo,,E

D -~O"TO·•O" D

~ ·lO"TO·Z0"­

-ZO"T0·10"D -D ,0•10 zo• c:J 10-10)0"0

~0·10 oo• -

Figure 1. Zones of plant hardiness in Minnesota from the United States Department of Agriculture Miscellaneous Publication No. 814, 1960 (U.S. map above)

7

615, so all opinions are based on other reports or in a few cases on observation of apparent salt tolerance. In the absence of precise information, salt tolerance is indicated in tables 1 and 2 simply as: susceptible to salt injury (- ), salt tolerant ( + ), or unknown (U).

ABSTRACT

Over 500 different accessions of woody and herbaceous plant materials were studied to determine their suitability for use as ground covers on highway slopes in Minnesota.

Plant materials are separated according to performance: 34 are recommended for use and 71 are recommended for limited use in Minnesota. Plants not recommended are also re­viewed.

Plant descriptions, geographic range, hardiness, site limi­tations, salt tolerance, propagation, availability, establishment, culture, and maintenance requirements of the recommended materials are discussed.

Several cultural investigations associated with the 6-year program are also reported.

The Matter of Names The names of plants in this report, with few exceptions,

are those in the current horticultural vernacular in Minnesota and surrounding states. The names largely correspond to those of "Standardized Plant Names," (1942), except where too cumbersome or unrealistic to be acceptable.

Common names are used with botanical names in the tables to avoid misinterpretation and identification problems. By their nature, common names are unstable and often local in application. A given species may have several common names or a name that is applied to unrelated species in differ­ent parts of the country.

The common names of plants are capitalized throughout this report for clarity and emphasis.

I. Evaluation Categories

The evaluations are presented in three different categories: ( 1) ground covers recommended, ( table 1 ) , plants warranting consideration for extensive use within the range of conditions prescribed; ( 2) plants recommended for limited use, ( table 2), plants with specific limitations or local adaptability; and (3) plants not reco:'11mended or not sufficiently evaluated, (table 3 > '. plants lackmg hardiness or adaptability to highway con­d1t10ns.

Recommended varieties are listed with brief annotations to describe t~e ~haracter, application, and limitations of the plants.

The _hm1ted recommendation category includes some plants with landscape value and unquestionable merit as ground covers, but less successful under Minnesota conditions tha!1 those &iven full recommendation. In the right situation a given species_ may equal or exceed the performance of some of the more highly recommended varieties. This category in­cludes many plants that need further evaluation before a firm recommendation can be made.

Species unsatisfactory for use under Minnesota roadside conditions are those not recommended. Some in this category may be excellent ground covers under cultivated conditions or in warmer climates.

1 + = tolerant, U = tolerance unknown, - = intolerant. 2

A companion crop which germinates early and aids in initial soil stabilization.

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Table 1. Ground covers recommended for use on high­way slopes in Minnesota

BEARBERRY (Arctostaphylos uva-ursi) (figure 2) Zone 2

Plant Description: A prostrate evergreen trailing shrub form­ing a mat-like cover with small leaves and white inconspicu­ous flowers. To 8 inches.

Range: Throughout northern part of the world-native to northern Minnesota.

Site Tolerance: Full sun or partial shade, poor acidic (sandy or rocky) soils.

Salt Tolerance: +.1

Propagation: Grown from cuttings and established in pots. Can be difficult to transplant. Sods of wild material may be placed directly on slopes. Cuttings of mature wood or early spring cuttings of rooted stem sections.

Establishment and Culture: Grown from transplants or rooted cuttings. Plant 1 foot apart ( 1,000 per 1,000 square feet). More research needed on establishment requirements. A vigorous spreader requiring no attention once established. No insect or disease problems.

Availability: Not readily available. Should be contract grown.

CROWNVETCH ( C oronilla varia) ( figure 3) Zone 2

Plant Description: Perennial legume, 1-2 feet tall. One plant can cover 6 feet of ground. Plants mound up and form a dense ground cover. Pink flowers.

Range: Native of Europe and Asia but escaped along road­sides and fields in Northeastern and Central U.S.

Site Tolerance: Best in full sun but tolerates limited shade. Good in dry infertile situations and on banks. Faster grow­ing with adequate moisture after establishment. Does not tolerate less than 6.5 pH-prefers circumneutral soils.

Salt Tolerance: U.

Propagation: Division of plants or roots or by seed.

Establishment and Culture: Establish by seed, crowns or transplanting of seedlings. Slow to establish and poor com­petitor first year but produces excellent cover by second or third season. Use with nurse crop2 of red clover, K 31 fescue or ryegrass is suggested at 20 pounds/acre Crown­vetch to 25 pounds/acre nurse crop. If using plants, space 1 ½ feet apart ( 440 plants per 1,000 square feet).

Availability: At most commercial seed houses.

Special inoculants should be employed when planting seed ( obtained when purchasing seed) to ensure proper growth in the absence of heavy nitrogen fertilization. With properly inoculated seed, a fertilizer ration of 1-2-2 should be used at rates no more than 60 pounds actual nitrogen per acre. Holds steep banks with large root system and heavy cover of leaves, which even in winter offer good soil protect1~n. Recommended on clay banks where rough cover is permis­sible.

DAYLILY, TAWNY (Hemerocallis fulva) (figure 4) Zone 2

Plant Description: Hardy perennial lily-like plants with long leaves and single or double flowers. Height to 3 feet. Long leaves produce heavy ground cover.

Range: Native of Asia but widely naturalized in the United States.

Site Tolerance: Adapted to a wide range of well-drained soils.

Table 1. Ground covers recommended for use on high­way slopes in Minnesota (continued)

Salt Tolerance: + Propagation: By division of root stock. Easily increased. Seeds

rarely produced. Establishment and Culture: Easily established from crowns.

Space 1 ½ feet apart ( 440 plants per 1,000 square feet). Little maintenance required.

Availability: Readily available from nurseries.

DOGWOOD, REDOSIER (Cornus stolonifera) (figure 5) Zone 2

Plant Description: A spreading shrub to 10 feet. Through the program a new lower-growing variety was introduced called 'Isanti.' Its inclusion as a ground cover is based on its height (under 6 feet) and its ability to spread by stolons.

Range: Throughout North America except for the southeast­ern United States.

Site Tolerance: Widely adapted to all but very dry sites; most common on moist soils.

Salt Tolerance: U. Propagation: Cuttings, both hard and softwood. Cuttings root

easily.

Establishment and Culture: Established by transplants. Plant 3 feet apart (110 per 1,000 square feet). No special cultur­al requirements needed.

Availability: Isanti, the low-growing form, is beginning to be available. Propagation material can be supplied to nurseries.

Isanti is a very dense shrub ideal for screening effects and hedges. It has the same cultural requirements as ordinary Redosier Dogwood. This is one of the significant new vari­eties developed in the program and the only one sufficiently tested to be named and introduced to the nursery trade.

JUNIPERS

The junipers comprise a large group of evergreen trees and shrubs, some of which are prostrate in habit. The low, pros­trate types are of primary interest for ground covers. Varie­ties and selections from five species have been included in these investigations.

JUNIPER, ARCADIA and JUNIPER, SKANDIA (Juni­perus sabina 'Arcadia' and 'Skandia') (figures 6 and 7) Zone 2

Plant Description: These two junipers are low-growing selec­tions of Savin Juniper. Skandia is the lower growing ( 1 branches and dense form. They are markedly hardier than foot) while Arcadia is taller ( 1 ½ feet) , with arching branches and dense form. They are markedly hardier than typical Savin Juniper, which is of borderline hardiness in Minnesota.

Ran~e: Both varieties originated in Canada from seed ob­tamed from the Ural Mountains, U.S.S.R. Cultivated in U.S. and Canada.

Site Tolerance: Quite intolerant of poorly drained soils. Ac-cepts a broad pH range.

Salt Tolerance: U.

Propagation: By cuttings.

Establishment and Culture: Transplants of balled and bur­lapped stock. Plant 2 feet apart (250 per 1,000 square feet). Maintenance minimal once established.

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Suggested for mass plantings on banks. Availability: Both available-Skandia not as common as Ar­

cadia.

JUNIPER, CREEPING (Juniperus horiwntalis) (figure 8) Zone 2

Plant Description: Prostrate and creeping evergreen forming low mats. Produces long runners which may root. Turns purplish color in winter. To 15 inches.

Range: North America from Nova Scotia west to Montana. Found on sea cliffs and gravelly slopes.

Site Tolerance: Prefers dry sandy or rocky soils. Tolerates sun or partial shade. Tolerant of both acid and alkaline soils.

Salt Tolerance: +. Propagation: Possible from seed. If growing varieties, by cut­

tings in August-October or by layering. Roots easily.

Establishment and Culture: Establish by transplants of balled and burlapped stock. Plant 3 feet apart ( 110 per 1,000 square feet). Once established requires little attention. Can be cut back and plants will become more heavily branched.

Availability: Many of the varieties in the following list (and especially Bar Harbor, Waukegan, and Hughes) are com­monly sold in nurseries.

Good for banks. The ground covering ability of this plant is superb, but most wild forms are of comparatively slow growth. Numerous varieties of this plant are in the nursery trade and vary considerably in plant form, color, foliage, tex­ture, and vigor. The following juniper varieties from the pro­gram are rated highly.

Varieties of Creeping Juniper

Name Zone Height Description

JUNIPER, ADMIRABILIS 2 1' practically same (Juniperus horiwntalis as creeping 'Admirabilis') juniper

JUNIPER, ADPRESSED 2 6" lower than (Juniperus horiwntalis creeping juniper 'Adpressa')

JUNIPER, BAR HARBOR 1 l' steel-blue (Juniperus horizontalis needles, 'Bar Harbor') more compact

JUNIPER, BLUE CREEPING 2 1' practically same, (Juniperus horiwntalis but bluer glauca) needles

JUNIPER, BLUE HORIZON 2 1' same as above (Juniperus horiwntalis 'Blue Horizon')

JUNIPER, BLUE RUG 2 1' good, spreading, (Juniperus horiwntalis 'Blue fast-growing Rug - sometimes sold as variety 'Wiltoni,' 'Wilton Carpet')

JUNIPER, FILICINUS- 2 1' same as MINIMUS creeping juniper (Juniperus horiwntalis essentially 'Filicinus-Minimus')

JUNIPER, FLAT CREEPING 2 1' same as above (Juniperus horiwntalis 'Glomerata')

Table 1. Ground covers recommended for use on high­way slopes in Minnesota (continued)

Name Zone Height Description

JUNIPER, HUGHES 2 (Juniperus horizontalis 'Hughes')

l' one of fastest growing varieties with good form and color

JUNIPER, LIVIDIS 2 l' good color and (luniperus horizontalis 'Lividis') form

JUNIPER, MARSHALL 2 l' same as above (Juniperus horizonta/is 'Marshall')

JUNIPER, WAUKEGAN 2 l' very good long-(Juniperus horizonta/is 'Douglasii') established var-

iety, blue in summer, pur-pie in winter

JUNIPER, JAPANESE GARDEN (Juniperus procumbens) (figure 9) Zone 3

Plant Description: Compact prostrate spreading juniper with short bluish green, sharp-pointed leaves. Height 1 foot.

Range: Native of Japan, long cultivated in United States.

Site Tolerance: Well-drained soils and circumneutral to alka-line in pH.

Salt Tolerance: U.

Propagation: Readily propagated by cuttings or seed.

Establishment and Culture: Transplant of balled and bur-lapped stock. Plant 2 ½ feet apart (120 per 1,000 square feet). Needs no special culture.

Availability: Readily available commercially.

This is one of the finest appearing junipers. It hugs the ground closely producing a neat compact appearance. A dwarf form, variety 'Nana' is smaller but too slow in growth for highway planting recommendation.

JUNIPER, OLDFIELD, or PROSTRATE (Juniperus com­munis depressa) (figure 10) Zone 3

Plant Description: Low evergreen shrub to 3 feet high and several feet wide. Turns purplish-yellow in winter.

Range: From Newfoundland west to Minnesota. In Minnesota occurs along steep bluffs, river bottoms, throughout state except in the southwest prairie region.

Site Tolerance: Tolerates dry, rocky, and sandy soils-rather broadly site tolerant.

Salt Tolerance: U.

Propagation: By cuttings in fall or winter and also by seed.

Establishment and Culture: By transplants of balled and bur-lapp~d stock-best when young. Plant 3½ feet apart (ap­proximately 100 per 1,000 square feet). Needs little atten­tion. May be sheared.

Availability: Some cultivated varieties are available commer-cially.

!?or banks as erosion control species or for single low plants m l: ll:~ds~ape plan. Can be used throughout the state. The vanab1hty m form and mature height of different individuals of this species makes use of seedling populations undesirable. Two low-growing varieties which mature at about 18 inches have been selected under this project.

10

JUNIPER, PFITZER (Juniperus chinensis 'Pfitzeriana') (fig­ure 11) Zone 3

Plant Description: A shrubby juniper of flat-topped broadly pyramidal form, much used as a landscape material. In Minnesota it reaches 4-5 feet in height but is often lower. Branches spread outward and upward and branchlets droop.

Site Tolerance: Widely adapted to a range of soils if well drained.

Salt Tolerance: U. Propagation: By cuttings.

Establishment and Culture: Establish from transplants, balled and burlapped or container grown for general landscape use. Varieties of Pfitzer Juniper can be used in the same manner as Pfitzer where warranted.

Availability: Commonly available commercially. Varieties:

COMPACT PFITZER JUNIPER (Juniperus chinensis 'Pfitz­eriana Compacta')

lhree-four feet in height, somewhat slower in growth and more dense than Pfitzer. Branches horizontal at 1 foot above ground. Purple in winter. Establish from transplants.

ARCTIC PFITZER JUNIPER (Juniperus chinensis 'Arctic Pfitzer')

Four feet in height. Similar in form to Pfitzer w'.th bluish cast to foliage. Establish from transplants.

BLUE FFITZER JUNIPER (Juniperus C::inensis 'Blue Pfitzer')

Six feet in height. Similar to Pfitzer but blue. Establish from transplants.

JUNIPER, SARGENT (Juniperus chinensis 'Sargenti') (fig­ure 12) Zone 3

Plant Description: A low prostrate shrub-1 foot in height-stems prostrate with upright branches, eventually forms dense broad mass. Adult leaves gray-green.

Range: From Kurile Islands and Sakhalin, cultivated in Nor­thern U.S.

Site Tolerance: Adapted to wide range of well drained soils. Useful only in southern Minnesota.

Salt Tolerance: U. Establishment and Culture: Establish from transplants. Plant

2½ feet apart (200 per 1,000 square feet). No special cul­ture.

Propagation: By cuttings or by seed.

Availability: Fairly common in the nursery trade.

MILKVETCH, CICER (Astragalus cicer) (figure 13) Zone 3

Plant Description: Low-growing perennial legume-to 2 feet in height. Looks somewhat like Crownvetch-somewhat viny. Inconspicuous yellowish-white flowers.

Range: From Europe but grown occasionally in the U.S.

Site Tolerance: Tolerated circumneutral to alkaline soils <Pf 8.1 at Crookston). Does well on heavy and moderate s01 s -performance on sandy soils unknown.

Salt Tolerance: +. Propagation: By seed. If plants, plant 1 ½ feet apart ( 400 per

1,000 square feet).

Table 1. Ground covers recommended for use on high­way slopes in Minnesota (continued)

Establishment and Culture: Establish by seeding. No main­tenance required after establishment.

Availability: Limited, but should become more available in future.

Cicer Milkvetch is recommended as a bank stabilizing mater­ial. It establishes more quickly than Crownvetch and produces a plant of about equal size. Longevity in Minnesota is at least 5 years. Special bacterial inoculant must be used with the mil kvetches.

ROSE, KAMCHATKA (Rosa amblyotis) (figure 14) Zone 2

Plant Description: Shrub rose of vigorous suckering habit. Spreads rapidly by suckering from roots. To 3 feet.

Range: Kamchatka. Adapted throughout Minnesota.

Site Tolerance: Most well-drained soils.

Salt Tolerance: U.

Propagation: By seeds, cuttings, or division.

Establishment and Culture: Establish by transplants. Plant 3 feet apart ( 110 per 1,000 square feet). No special culture.

Availability: Will have to be contract grown as not commer­cially available.

SUMAC, FRAGRANT (Rhus aromatica) (figure 15) Zone 3

Plant Description: A woody shrub of dense branching habit. Leaves small and trifoliate. Reaches 6 feet on good soils.

Range: Eastern United States except coastal region.

Site Tolerance: Shows wide tolerance of dry soils.

Salt Tolerance: +. Propagation: By seeds or root cuttings.

Establishment and Culture: Establish with transplants. Plant 2-3 feet apart (200 per 1,000 square feet). Little mainten­ance.

Availability: Not commonly available and will have to be con­tract grown.

Covers dry banks and slopes with a low scrambling type cover. Similar to Skunkbush (R. trilobata).

SUMAC, SMOOTH (Rhus glabra) (figure 16) Zone 2

Plant Description: A woody shrub of open coarsely branching habit, spreads by underground stems. Usually under 10 feet, on poor sites often much less. Colorful leaves in fall.

Range: Throughout United States-in Minnesota on dry sites especially.

Site Tolerance: A wide variety of soils including sandy gravel­ly knolls-both sun and partial shade.

Salt Tolerance: +.

11

Propagation: By seed or by root cuttings.

Establishment and Culture: Establish by transplants. Plant 2-3 feet apart ( 200 per 1,000 square feet). Once established no maintenance needed.

Availability: Commercially available on a limited scale. Has the ability to invade and occupy poor soils producing an open stand that permits grasses and other plants to grow be­neath. Excellent species for areas to be taken out of mainten­ance. A closely related species, Shining Sumac (Rhus copal­lina) also performed well in nursery plantings. It succeeds well in dry soil. Outstanding, with dark green glossy foliage.

TREFOIL, BIRDSFOOT (Lotus corniculatus) (figure 17) Zone 3

Plant Description: Perennial legume, to 1 foot, but often pros­trate in habit, as with Empire variety. One plant covers 2½ feet. Small yellow flowers.

Range: Native of Europe but has escaped and is found on roadsides and pastures throughout northern and central North America.

Site Tolerance: Does well in poor soils, very drought and heat resistant. Can grow in pH range of 4.4-7.9. Tolerates both dry and moist situations.

Salt Tolerance: +. Propagation: By seed, by crown division, and by cuttings.

Establishment and Culture: Plant at depth of ¼ to ½ inch. If plants, plant 1 foot apart (1,000 per 1,000 square feet). Needs inoculum, as do all legumes. Fertilizer ratios sug­gested are: 0-10-30 or 1-2-2. May be a poor competitor during establishment and weed control measures should be incorporated, such as TCA at 8 pounds/acre, Dalapon at 4 pounds/acre or 2,4-DB at ½ pound/acre. Nurse crops recommended are Alta Fescue, Ryegrass, or Oats. Best when summer seeded. Can be mowed.

Availability: Empire readily available, with inoculant, at seed houses.

A hardy rather trailing plant for covering dry banks through­out state.

Birdsfoot Trefoil is a plant coming into general use as a forage and pasture legume. The principal forage type is the tall upright variety Viking. Empire is a pasture form varying from nearly prostrate to upright. Several selections are on trial but are not yet commercially available.

Varieties: CILIATE BIRDSFOOT TREFOIL (Lotus corniculatus cili­atus)

Practically the same as Birdsfoot Trefoil but of lower habit than Viking or Empire.

ELLIOTT'S BIRDSFOOT TREFOIL (Lotus corniculatus "Elliott's Strain")

A low-growing selection of Empire.

LEO BIRDSFOOT TREFOIL (Lotus corniculatus 'Leo')

A new selection from Canada. Of superior seedling vigor to Empire but not sufficiently tested.

(

Table 2. Plants recommended for limited use on Minnesota roadsides

Plant Plant Salt Evaluation, comments, and Name zone height Spacingec Type tolerance* availability

ALFALFA, PROSTRATE (figure 18) 3 1½' herbt + Spreads rapidly. Of initial promise, (M edicago saliva form) Not generally available.

ALFALFA, CARSTIEN 3 1' 1' herbt + Clonally propagated selection with (M edicago carstiensis) fine textured foliage. Could be use-

ful on limited areas. Establish by rooted cuttings or division. Con-tract grown.

ALFALFA, PIRONE (figure 19) 3 1' herbt + Performed well in early evaluation. (Medicago pironae) Continues to perform well on alka-

line soils at Crookston. Full sun. Establish from seed.

ALFALFA, SICKLEPOD (figure 20) 3 3' 1' herbt + This alfalfa has performed well (Medicago falcata) only on barren glacial till. Estab-

lish from seed or plants. Not com-monly available.

BARBERRY, DWARF JAPANESE 4 2' 1-1½' woody u Ornamental - may h::.ve some (Berberis thunbergi minor) value under culitivated conditions.

Establish from transplants. Avail-able.

BARRENSTRAWBERRY (Waldsteinia fragarioides)

(figure 21) 2 6" 1' herbt u A native strawberry-like plant adapted to dry sandy wils. Yell ow flowers. Needs further evaluation. Acidic to circumneutral soils, full sun or shade. Establish with trans-plants. Not readily available.

I ~ BAYBERRY (figure 22) 3 3' 2' semi + Valuable semi-evergreen. Acidic to , (Myrica pensylvanica) evergreen circumneutral saline soils, full sun.

shrub Readily available.

BITTERSWEET, ORIENTAL 4 2' 2' woody u For use on banks with good soil in (Celastrus orbiculata) vine southern Minnesota. Must be

contracted.

BLACKBERRY,ALLEGHENY 3 2-3' 2' decumbent u Of some value where a scrambling (figure 23) woody shrub thorny plant can be used. Adapted (Rubus allegheniensis) to many soils. Available from

wild stock. Propagate from root cuttings.

\ ', BLUEBERRY, LOWBUSH 2 2' 1½' woody u Native low shrub, persistent once it (Vaccinium angustifolium) is established. Requires moisture to

grow well. For use in mixed vegeta-tion. Acidic soils, full sun or part , shade. Available.

• Spacing at planting time in intervals. 1 foot apart= 1,000 plants/1,000 square feet 2 feet apart= 250 plants/1,000 square feet 3 feet apart = ll0 plants/1,000 square feet

t Herbaceous or nonwoody

* + = tolerant, U = tolerance unknown, - = susceptible. §=annual

12

Table 2. Plants recommended for limited use on Minnesota roadsides (continued)

Plant Plant Salt Evaluation, comments, and Name zone height Spacing* Type tolerance:!: availability

BUSHHONEYSUCKLE, DWARF 2 2-3' l½-2' woody u Recommended for dry banks. A (Diervilla lonicera) native species found on acid and

circumneutral soils. Tolerates shade and full sun. Inconspicuous flow-ers. Establish from transplants. Will have to be contracted.

BUSHHONEYSUCKLE, GEORGIA 3 4-5' 2½-3' woody u Recommended for similar situa-(figure 24) tions as Dwarf Bushhoneysuckle, (Diervilla rivularis) but is more vigorous. Available.

BUSHHONEYSUCKLE, SOUTHERN 3 4-5' 2½-3' woody u Recommended for similar situations (Diervilla sessilifolia) as Georgia. More vigorous than

Dwarf Bushhoneysuckle. Avail-able.

CINQUEFOIL, DWARF SPRING 3 6" 1' herbt u Suitable only to fertile cultivated (figure 25) (Potentil/a verna 'Nana')

situations. Attractive plant hugging ground. Establish from transplants. Contract grown.

CINQUEFOIL, CINNAMONLEAF 4 6" 1' herbt u Vigorous, rather fine-textured. Not (Potentilla cinnafolia) adequately evaluated. Worthy of

further observation. Limited availability.

CINQUEFOIL, WINELEAF (figure 26) 2 6-12" 1' evergreen + Very attractive native evergreen (Potentilla tridentata) ground cover adapted to poor

rocky and sandy soils. Available locally.

CINQUEFOIL, SHRUBBY 3 1-3' 2½' woody u All Shrubby Cinquefoil cultivars (Potentilla fruticosa) are potentially useful, white to ye!-

Varieties: low flowers, silvery foliage. More Forresti adapted to mass planting effects Friedrichseni (figure 27) than ground cover. Circumneutral Gold Drop to alkaline soils, full sun. Particu-Irving ( figure 28) larly adapted to alkaline soils. Es-White Gold tablish from transplants. Available.

CLOVER, ALSIKE 3 1½' 1' herb-r Not reliable on perennial basis. Per-(Trifolium hybridum) sists during wet seasons - declines

in dry years. May be used in grass seeding mixtures. Available.

CLOVER, RABBITFOOT 3 1' 1' herb-r + Suited to dry soils. Common on (Trifolium arvense) highway shoulders in northern

Minnesota. Acidic to circumneutral sandy soils, full sun. Establish from seed. Available.

CLOVER, RED 3 2-3' 1' herbt A vigorous clover of value mixed (Trifolium pratense) with grass species. Establish from

seed. Available.

CLOVER, WHITE (figure 29) 3 1½' 1' herbt Not as vigorous as Alsike Clover. (Trifolium repens) Available.

13

Table 2. Plants recommended for limited use on Minnesota roadsides (continued)

Plant Plant Salt Evaluation, comments, and Name zone height Spacing* Type tolerance* availability

CLOVER, ZIGZAG (figure 30) 4 1' 1' herbt u Spreading clover with some prom-(Trifolium medium) ise as highway material. Performed

well in limited plantings. Needs further evaluation. Must be con-tract grown.

CORALBERRY, INDIANCURRANT 2 3' 2' woody u Similar to W olfberry but somewhat (Symphoricarpos orbiculatus) smaller. Same application. Acid to

somewhat alkaline soils, full sun. Establish from transplants. Avail-able. Don't use hybrids, e.g., Chen-aults.

COWBERRY (figure 31) 2 1' 1' woody + A broadleaf evergreen of some (Vaccinium vitis-idaea) evergreen potential on acid soils. Shiny dark

shrub leaves make the plant very attrac-tive. A rare native of northern Minnesota. Acid soils and full sun. Must be contract grown.

CREEPER, THICKET (figure 32) 3 1' l½-2' woody u Native deciduous vine adapted to (Parthenocissus inserta) shady conditions. Does not result

in uniform dense cover. Will climb. Must be contracted.

CREEPER, VIRGINIA (figure 33) 4 1' l½-2' woody + Closely related to Thicket Creeper (Parthenocissus quinquefolia) but more vigorous. Deciduous

vine - potential use on shaded banks. Will climb to 50 feet. Es-tablish by transplant. Engelmann variety available.

FLEECEFLOWER, LOW JAPANESE 4 3' 1½' herbt u Very vigorous, strongly spreading (Polygonum cuspidatum compactum) once plant is established. Tops

killed by frost. Can become nui-sance in gardens. Available.

FLEECEFLOWER, REYNOUTRIA 4 2-3' 1½' herbt + Attractive pink flowering, vigorous (figure 34) and competitive. Once established (Polygonum reynoutria) will crowd out most weeds. Tops

killed back by frost. Establish by pot grown plants. Needs further evaluation. Available.

GOATSRUE 4 4' herbt u Tolerates highly alkaline soils. Stiff (Galega officinalis) upright stems. May be of value on

tight, high pH soil situations.

HONEYSUCKLE, LILAC (figure 35) 4 4' 1½-2' scrambling u Recommended as promising dense (Lonicera syringantha) shrub shrub. Performed well in nursery

tests. Not adequately tried on road-sides. Establish from transplants. Must be contract grown.

JUNIPER, SAN JOSE 4 1' 2-3' woody u Very low-growing. Needs further (Juniperus chinensis 'San Jose') evergreen evaluation. Not too commonly available.

14

Table 2. Plants recommended for limited use on Minnesota roadsides (continued)

Plant Plant Salt Evaluation, comments, and Name zone height Spacing* Type tolerancet availability

JUNIPER, SPREADING PROSTRATE 2 2' 2-3' woody u Spreading form. Of possible use -(Juniperus communis depressa evergreen needs further evaluation. Not too 'Effusa') commonly available.

LESPEDEZA, RUSH (figure 36) 4 3' herbt u Provides good cover, but turns (Lespedeza hedysaroides) brown at first frost. Crownvetch or

Cicer Milkvetch superior for ground cover purposes. Establish from seed. Must be contract grown. Seed from USDA Soil Conservation Service (SCS).

LESPEDEZA, SCHIMID 4 2-3' herbt u Same as Rush Lespedeza. Seed from (Lespdeza daurica schimidae) SCS.

MILKVETCH, SICKLEPOD (figure 37) 3 3' herbt + Vigorous on some sites but does (Astragalus falcatus) not produce as good a cover as

Cicer Milkvetch. Establish from seed. Must be contract grown.

M0CKSTRA WBERRY, INDIA 3 6" 1' herbt u Spreading strawberry-like plant (figure 38) with possible limited value. Mostly (Duchesnia indica) garden ornamental. Acid to circum-

neutral soils. Establish from stol-ons. Availability limited.

PARTRIDGEPEA (figure 39) § 2' annual u For use as temporary cover on (Cassia f asciculata) sandy soils. Native legume. Estab-

lish from seed. Available.

PEASHRUB, RUSSIAN (figure 40) 3 6' 2-3' woody u Suited for use on long slopes or (Caragana frutex) where large size is not limiting

factor. Establish with transplants. Available.

PEA VINE, PERENNIAL ( figure 41) 3 3' vine u Perennial vine - good for initial (Lathyrus latifolius) cover. Toxic to cattle. Available.

PERIWINKLE HERBACEOUS 4 1' 1' herbt u Suggested for trial only in pro-(figure 42) ' evergreen tected places. Establish from trans-/Vinca herbacea) vine plants or sods. Available.

PETUNIA, QUICKSILVER (figure 43) § 8" herbt u Has reseeded itself remarkably in (Petunia parviflora 'Quicksilver') the Crookston area. Produces a

mounded solid cover persisting until cold weather. Small red flowers throughout season. Seed may be difficult to acquire.

PHLOX, ALASKA (figure 44) 3 6" 1' herbt u Compact dark-green, evergreen-/Phlox borealis) evergreen creeping phlox. Produces dense mat

with colorful pink flowers under fertile semicultivated conditions. Circumneutral soils, full sun, ·or part shade. Establishment by trans-plants. Must be contract grown.

15

Table 2. Plants recommended for limited use on Minnesota roadsides (continued)

Plant Plant Salt Evaluation, comments, and Name zone height Spacing"' Type tolerance:j: availability

PHLOX, AMOENA 3 6" 1' herbt u Attractive creeping phlox with col-(Phlox amoena) semi- orful lavender bloom. Produces

evergreen dense matted ground cover in fer-tile semicultivated situations. Estab-lish by transplants. Must be con-tract grown.

PHLOX,BLUE 4 1' 1' herbt u Native phlox, occasionally invades (Phlox divaricata) roadsides with other native plants,

but does not produce a mat-like cover. Must be contract grown.

PINK, MAIDEN (figure 45) 3 1' 1' herbt u An excellent ornamental garden (Dianthus deltoides) ground cover - may be suited to

limited use in areas permitting high maintenance. Establish with trans-plants. Available.

POLYGONUM, MAGIC CARPET § 4" herbt u A creeping annual which reseeds. (figure 46) annual May have some value in temporary (Polygonum capitatum 'Magic Carpet') plantings. Establish - seed.

Available.

RASPBERRY, JAPANESE TRAILING 3 3' 2' woody u Hardy trailing ground cover for (figure 47) fertile sites with adequate moisture. (Rubus parvifolius) Establish from transplants. Soil

Conservation Service has basic stock.

SAGE, FRINGED (figure 48) 2 l½' 1' herbt u Limited value on dry sites. A native (Artemisia frigida) species tolerant of alkaline soils.

Needs full sun. Establish from transplants. Must be contract grown.

SNOWBERRY, COMMON (figure 49) 3 4' 3' woody + Not adequately tested- similar to (Symphoricarpos a/bus) wolfberry. Establish from trans-

plants. Available.

SOUTHERNWOOD, DWARF (figure 50) 3 1-3' l½-2' semi- + Requires reasonably fertile soils -(Artemisia abrotanum 'Nana') evergreen tolerates alkaline conditions. Re-

quires little care and may be c~t back. Doesn't persist on poor sites. Some dying out due to disease. Must be contract grown.

SPEEDWELL, DRUG 3 1' 1' herbt u Hardy plant adapted to moist sandy (Veronica officinalis) perennial slopes. Remains green und~r snow.

Acidic to circumneutral s01ls, full sun or shade. Naturalized in no~th-ern Minnesota. Limited aggressive character. Establish from trans-plants. Available.

SPEEDWELL, GERMANDER 3 1' 1' herbt u Useful under same conditions as (Veronica chamaedrys) perennial Drug Speedwell. Acidic-circum-

neutral soils, full sun or shade. Es-tablish from transplants or sods. Available.

16

Table 2. Plants recommended for limited use on Minnesota roadsides (continued)

Plant Plant Salt Evaluation, comments, and Name zone height Spacing* Type tolerance:t: availability

SPIREA, BILLIARD (figure 51) 4 3' 3' woody u Spreading shrub - spreads slowly (Spiraea billiardi) on fertile sites to form solid mass.

Establish from transplants. Avail-able.

SPIREA, DWARF GARLAND 4 1' 1' woody u Suited only to fertile, cultivated (figure 52) sites. Establish from transplants. (Spiraea arguta compacta) Available.

STEPHANANDRA, CUTLEAF 4 3' 2' woody u Low arching plant - tends to tip-(Stephanandra incisa 'Crispa') root in the manner of black rasp-

berries. Establish from transplants. Limited availability.

STEPHANANDRA, DWARF CUTLEAF 4 2' 1' woody u Smaller form than Cutleaf, of more (figure 53) arching habit. Full sun or part (Stephanandra incisa 'Crispa Nana') shade. Available.

STONECROP, TWO-ROW (SEDUM) 4 4' 1' herbt u Has persisted for 5 years on 1-494 (figure 54) site. Adapted to stony banks, par-(Sed111n spurium) ticularly exposed bedrock. Of very

limited use. Establish from trans-plants or sprigged. Available.

SUMAC, ROCKY MOUNTAIN 3 8' 2-3' woody u Similar to but less hardy than com-(R/111s glabra cismontana) mon Smooth Sumac. Establish from

transplants. Must be contract grown.

SWEETFERN (figure 55) 2 2-3' 2' woody + A native ground cover of excellent (Comptonia peregrina) qualities. Acid soils and full sun.

Establish from transplants. Avail-able.

VETCH, BIRD (figure 56) 3 2' herbt u Hardy perennial vetch similar to (Vicia cracca) vine Hairy Vetch. Suggested for trial be-

cause of perennial character. Seed from SCS.

VETCH, HAIRY 3 2' herbt u This species is in common use. (Vicia vi/losa) annual Suitable for use as a soil builder

and temporary cover or in grass mixtures. Acidic to circumneutral soils, full sun. Establish from seed. Available.

VIRGINSBOWER (figure 57) 3 2' 1½' vine u Recommended as viny ground cov-(Clematis virginiana) er. A common native that frequent-

ly covers railroad banks with a thick growth. Needs more trial as experimental planting on rough banks. Best in full sun, but will tol-erate some shade. Will climb to 15 feet. Establish from transplants. Available.

17

Table 2. Plants recommended for limited use on Minnesota roadsides (continued)

Plant Plant Salt Evaluation, comments, and Name zone height Spacing* Type tolerance:t: availability

WOLFBERRY (figure 58) 2 4' 2' woody u Hardy native - may be useful on (Symphoricarpos occidentalis) dry banks. Easily propagated.

Broadly adapted to various soil pH's. Full sun. Establish from cut-tings and division. Must be contract grown.

WORMWOOD, SILVERMOUND 3 1' 1' herbt u Limited value, suitable only for (Artemisia schmidtiana 'Silvermound') decorative plantings permitting

relatively high maintenance. Toler-ates neutral or alkaline soils. Full sun. Establish from transplants. Available.

WORMWOOD, TALL 2 2-3' herbt u A native plant useful only as a (Artemisia caudata) temporary soil cover on light sandy

soils. Tolerates a wide range of pH. Requires full sun. Establish from seed. Must be contract grown for seed.

YUCCA, ADAMSNEEDLE (figure 59) 4 4' 2-3' herbt u Does not produce an adequate soil (Yucca filamentosa) cover. Use for decorative effect on

dry banks. Establish from plants. Available.

• See footnote references, page 12.

Table 3. Plants not recommended or not sufficiently evaluated for Minnesota roadsides

Name

ALFALFA, YELLOW-FLOWERED PROSTRATE (Medicago sativa form)

ALFALFA, BLUE (Medicago coerulea)

AMORPHA, LEADPLANT (Amorpha canescens)

AMORPHA, MOUNTAIN-INDIGO (Amorpha glabra)

ANTHYLLIS Anthyllis cornycina Anthyllis cytisoides Anthyllis hamosa Anthyllis lotoides Anthyllis vulneraria

* Herbaceous or nonwoody.

Plant zone

3

3

3

3

1

Plant height

6"

2'

2'

5'

l'

18

Type

herb*

herb*

woody

woody

herb*

Evaluation, comments, and availability

Dense, non-creeping, prostrate form of potential interest.

Not competive under test conditions.

A native low shrub, does not produce heavy enough cover to be of use alone. Establishment slow. Requires near neutral or slightly alkaline soils and full sun.

Similar to Leadplant Amorpha but insufficiently hardy. Near neutral soils and full sun or part shade. Establish from seed or transplants.

No species of anthyllis was recommended over clovers. All re­quire near neutral soils and full sun.

Table 3. Plants not recommended or not sufficiently evaluated for Minnesota roadsides (continued)

Plant Plant Evaluation, comments, and Name zone height Type availability

BROOM 5 woody Not hardy in Minnesota. (Cytisus sp.)

BROOM 5 woody Not hardy in Minnesota. (Cytisus sp. 'Choice Mixture')

BROOM 6 1½' woody Not hardy in Minnesota. (Cytisus podolicus)

BROOM, PROSTRATE PURPLE 4 1' woody Recommended only where it can (Cytisus purpurea procumbens) be maintained.

BUGLE, CARPET 5 6" herb* A good creeper but hardiness is in-(Ajuga reptans) sufficient for general use in Min-

nesota. Indifferent as to soil and tolerates full sun or shade.

BUGLE, METAI ICA-CRISPA 5 6" herb* A noncreeping ground cover with (Ajuga pyramidalis 'Metalica-crispa') colorful foliage. Not fully hardy

in Minnesota.

BUGLE, GENEVA 5 8" herb* A noncreeping ground cover not (Ajuga genevenis) fully hardy in Minnesota. Adapted

to a wide range of soils, will grow in full sun or shade.

CANDYTUFT, JORDAN 4 6" semi- Suited for limited use with moder-( I beris jordani) woody ate maintenance. A low decorative

evergreen plant somewhat woody at the base.

CORALBERRY, CHENAULT 5 2' woody Not hardy. (Symphoricarpos X chenaulti)

CORALBERRY, HANCOCK 5 2' woody Not fully hardy, low dense variety. (Symphoricarpos X chenaulti 'Hancock')

CINQUEFOIL 4 1' herb* Failed to grow. (Potentilla megalantha)

CINQUEFOIL, BEAUTY 4 1' herb* Adapted for ornamental use under (Potentilla pulcherrima) cultivated situations.

CINQUEFOIL, BUCCOAN 4 1' herb* Does not produce adequate cover. (Potentilla bucconana)

CINQUEFOIL, BUTTERCUP 4 1' herb* Does not produce adequate cover. (Potentilla ranunculus)

CINQUEFOIL, CI EFT 3 (Potentilla fissa)

1' herb* Does not produce adequate cover.

CINQUEFOIL, CUFF 3 3' herb* European species - does not pro-( Potentilla rupestris) duce adequate cover.

20

Table 3. Plants not recommended or not sufficiently evaluated for Minnesota roadsides (continued)

Plant Plant Evaluation, comments, and Name zone height Type availability

CINQUEFOIL, COLOMBIAN 5 1' herb* Does not produce adequate cover. 1 Potentilla andicola)

CINQUEFOIL, CRANTZ 4 4" herb* Does not produce adequate cover. (Potentilla crantzii)

CINQUEFOIL, CREEPING 2 2' herb* Not aggressive enough for ground (Potentilla reptans) cover. May have some value on

poor soils.

CINQUEFOIL, RUBY UNDERSNOW 3 1' herb* Does not produce adequate cover. / Potentilla argyrophylla atrosanguinea)

Cl~QUEFOIL, SILVERWEED 3 1' herb* Vigorous spreading perennial -I Potentilla anserina) attractive appearance when green

but subject to browning in summer.

CINQUEFOIL, SULFUR 3 3' herb* Weedy species - does not produce I Potentilla rec ta) adequate cover.

CLEMATIS, GOLDEN 5 2' woody Not hardy enough for roadside use. (Clematis tangutica) Climbs to 10 feet.

CLEMATIS, ORIENTAL 5 2' woody Not sufficiently hardy for roadside. !Clematis orientalis) vine Will climb to 15 feet.

CLEM A TIS, SCARLET 3 1' vine An excellent ornamental but not !Clematis texensis) vigorous enough for highway use.

CLEMATIS, SWEETAUTUMN 4 2' vine A strong vine, not hardy enough for (Clematis paniculata) use on exposed roadside banks.

Will climb to 20 feet.

CLOVER, BURDOCK 3 1' herb* Not aggressive enough for a ground (Trifolium lappaceum) cover.

CLOVER, EGYPTIAN 3 1' herb* Not aggressive enough for a ground (Trifolium alexandrium) cover.

CLOVER, FOAM 4 1' herb* Not aggressive enough. (Trifolium spumosum)

CLOVER, KURA - 3 1' herb* Not sufficiently competitive. (Trifolium ambiguum)

CLOVER, MOUNTAIN 3 /Trifolium montanum)

1' herb* Not sufficiently competitive.

21

Table 3. Plants not recommended or not sufficiently evaluated for Minnesota roadsides (continued)

Plant Plant Evaluation, comments, and Name zone height Type availability

HONEYSUCKLE, TRUMPET 4 2' woody Hardy only in southern Minnesota (Lonicera sempervirens) vine - not vigorous enough for a

ground cover.

HONEYSUCKLE, WOODBINE 5 2' woody Not vigorous enough for forming a (Lonicera periclymenum) cover and not hardy. Will climb.

HUCKLEBERRY, BLACK 3 2-3' woody Sandy acid soils. May have a (Gaylussacia baccata) limited application.

IVY, BOSTON 5 ( Parthenocissus triscuspidata)

1' woody Not hardy enough for roadside use.

IVY, BULGARIAN 5 1' vine Not fully hardy. Useful only as a (Hedera helix 'Bulgaria') evergreen garden ground cover. Acid to cir-

cumneutral soils. Full sun or shade. Will climb.

IVY, OGALLALA 5 1' vine Same as Bulgarian. (Hedera helix 'Ogallala') evergreen

JUNIPER, ALPINE 2 6" woody Insufficient evaluation. (Juniperus horizontalis evergreen 'Alpina')

JUNIPER, ANDORRA 5 1' woody Tends to burn in winter. Does not (Juniperus horizontalis evergreen always form adequate ground cover. 'Plumosa')

JUNIPER, BLUISH CREEPING 2 1' woody Color variant of Creeping Juniper. (Juniperus horizontalis evergreen Insufficient evaluation. 'Subglaucus')

JUNIPER, BLUE DANUBE 4 2' woody Insufficient evaluation. (Juniperus sabina evergreen 'Blue Danube')

JUNIPER, BLUE VASE 2 1' woody A nonspreading upright variety. (Juniperus horizontalis evergreen 'Blue Vase')

JUNIPER. BROADMOOR 4 2' woody Insufficient evaluation. Low, (Juniperus sabina 'Broadmoor') evergreen hardier selection similar to Arcadia

Juniper.

JUNIPER, COMPACT ANDORRA 2 1' woody Subject to winter burn. Slow-(Juniperus horizontalis evergreen growing and of good form. 'Plumosa Compacta')

JUNIPER, DWARF JAPANESE GARDEN 4 1' woody A fine ornamental but too slow. (Juniperus procumbens evergreen 'Nana')

24

Table 3. Plants not recommended or not sufficiently evaluated for Minnesota roadsides (continued)

Plant Plant Evaluation, comments, and Name zone height Type availability

. -----··--·--

JUNIPER, EXIMIUS CREEPING 2 1' woody Insufficient evaluation. (Juniperus horizontalis 'Eximius') evergreen

JUNIPER, IOWA 4 6' woody Upright - good for background (luniperus chinenis evergreen planting. Not a ground cover. 'Iowa')

JUNIPER, MOUNTAIN PROSTRATE 2 1' woody A compact slow-growing form of (Juniperus communis evergreen fine appearance - not vigorous saxatilis) enough for roadside use.

JUNIPER, SA VIN 5 3' woody Hardiness is borderline. (Juniperus sabina) evergreen

JUNIPER, SHORE 6 1' woody Excellent salt resistant ground cov-(J11niperus confer/a) evergreen er. Not hardy in Minnesota.

JUNIPER, SILVERY CREEPING 2 1' woody Insufficient evaluation. (Juniperus horizontalis 'Argenteus') evergreen

JUNIPER, TAMARIX 4 2-3' woody Not fully hardy on exposed sites. (J11niperus sabina evergreen tamariscif olia)

JUNIPER, VON EHREN 4 2' woody Does not form adequate cover. (luniperus sabina evergreen 'Von Ehren')

JACOBS LADDER 3 3' herb* Of value only in native mixtures. (Polemonium reptans)

LESPEDEZA, JAPANESE 4 3-4' woody Ragged, woody bushclover - up-(Lespedeza japonica right habit. Does not develop intermedia) good cover.

LICORICE 4 3' herb* Offers no advantage over native (G iycyrrhiza echinata) licorice (G. lepidota). Needs more

hardiness evaluation.

LICORICE 4 3' herb* Offers no advantage over native. (Giycyrrhiza glabra) Needs more hardiness evaluation.

LIPPIA 4 6" herb* Not reliably hardy. Also allows (Lippia cuneifolia) weeds' growth. Circumneutral to

alkaline soils.

LOCUST, PROSTRATE BLACK 5 3' woody Not reliably hardy in Minnesota. (Robinia pseudoacacia 'Prostrate') shrub

25

Table 3. Plants not recommended or not sufficiently evaluated for Minnesota roadsides (continued)

Plant Plant Evaluation, comments, and Name zone height Type availability

ST. JOHNSWORT 5 2' herb* Not hardy in Minnesota. (Hypericum polyphyllum)

SANDMYRTLE, ALLEGHENY 4 1' woody Broadleaf evergreen not reliably (Leiophyllum buxifolium subshrub hardy in Minnesota. 'Prostratum')

SARSAPARILLA, BRISTLY 3 2-3' woody A subshrub, woody at the base. For (Aralia hispida) use in mixtures on sterile sandy

soils. A native species on such soils.

SCORPIONSENNA 6 10' woody Not hardy in Minnesota. (Coronilla emerus)

SKUNKBUSH, DWARF 3 2' woody Unaggressive. A smaller form of (Rhus trilobata "Dwarf") shrub Skunkbush.

SNOWBERRY, MOUNTAIN 5 2' woody Not as hardy as Snowberry. (Symphoricarpos oreophilus)

SNOWBERRY, WASHINGTON 5 3' woody Not fully hardy. (Symphoricarpos hesperius)

SOAPWEED 4 3' herb* Not a sufficient ground cover. (Yucca glauca)

SPURGE, JAPANESE 5 1' evergreen Suited only to protected fertile sit-(Pachysandra terminalis) herb* uations. Acidic to circumneutral

soils, part or full shade.

SUMAC, HYBRID SMOOTH 3 8' woody Similar to, but not superior to (Rhus glabra borealis) shrub Smooth Sumac.

SUNROSE, ARCTIC 3 1' herb* Requires exacting care. Not suited (Helianthemum arcticum) for roadside planting. A garden

ground cover. Full sun.

SWEETCLOVER, CRIMEAN 4 2' herb* Low-growing sweetclover - needs (Me/ilotus taurica) further observation.

SWEETCLOVER, YELLOW 3 4' herb* Coarse, rank, irregular weedy (Melilotus officinalis) growth.

TANSYBUSH 6 4' woody Circumneutral to calcareous soils, (Chamaebatiaria millefolium) full sun. Unsatisfactory cover.

TREFOIL, DOUBLE BIRDSFOOT 2 1' herb* Ornamental selection that must be (Lotus corniculatus propagated vegetatively. 'Floro-pleno')

VETCH, COMMON 3 2' herb* Does not produce adequate ground (Vicia sativa) annual cover. Similar to Hairy Vetch.

28

Table 3. Plants not recommended or not sufficiently evaluated for Minnesota roadsides (continued)

Plant Plant Name zone height

VETCH, WOOLYPOD 4 (Vicia dasycarpa)

VIOLET 2 1Viola sp.)

VIRGINSBOWER; WESTERN 5 (Clematis ligusticifolia)

WHIN, DWARF 7 (U/ex nanus)

WILLOW, DWARF PUSSY 2 /Salix tristis)

WINTER CREEPER 5 /Euonymus fortunei)

WOLFBERRY, CHINESE 4 (Lycium chinense)

WULFENIA 3 ! W ulfenia bullii)

YELLOWROOT 5 ! Xanthorhiza simplicissima)

II. Evaluation of Plant Materials

EVALUATION OF PLANT MATERIALS AND HARDINESS

2'

6"

2'

1'

3'

3'

4'

1'

4'

The earlier years of the project were devoted to acquisition and evaluation of potential ground cover materials. Procure­ment was accomplished in the following ways: ( 1) from nur­senes, arboretums, botanical gardents, USDA Plant Introduc­tion Service, and experiment stations around the world; and .(2) .by individual exploration and collection of native mater­ials Ill natural habitat areas. There were over 500 accessions from 318 different species processed through the program; !27 of the plant materials evaluated in this project were col­lected directly from the wild.

. The procedure for evaluation included cataloging and veri­fymg each acquisition for positive identification. Following identification, materials were processed and if necessary pro-

29

Evaluation, comments, and Type availability

herb* A vigorous vine similar to Hairy Vetch. More evaluation needed.

herb* Not aggressive enough for highway ground cover. Native species of cir-cumneutral soils. Full sun or shade.

vine Similar to C. virginiana. Not fully hardy, no superiority over other clematis species. Circumneutral to slightly acid soils, full sun. Will climb to 15 feet.

woody Not hardy in Minnesota.

woody A low shrubby native willow oc-curring on sandy acidic soils and in full sun. Requires future evaluation.

vine Not hardy in Minnesota.

woody Does not compete well with grasses and weeds. Salt tolerant.

herb* An uncommon prairie native, suited only in prairie mixtures.

woody Not fully hardy in Minnesota. Needs shrub moist soil. Acidic to circumneutral

soils.

pagated for field planting or planted directly into field nur­series. Materials were evaluated qualitatively for: winter har­diness, propagation requirements, cultural requirements, and longevity.

Most of the evaluation was associated with field planting and observation of performance over the seasons for several years. Ability to survive Minnesota winters was the basis for judging winter hardiness in this project.

Cultural evaluation considered the following: minimum maintenance requirements, fertility needs, need for supple­mental watering and soil preference. Evaluations also included rate of growth, form, foliage characteristics, flowering and

Crownvetch and Empire Birdsfoot Trefoil was applied to a small area near the transplants. The transplants responded well and grew rapidly. Germination of the seeded area was satis­factory and an abundance of seedlings of both species was present by midsummer. Growth of Birdsfoot Trefoil was rapid but that of Crownvetch relatively slow.

The response of both species, however, was considered so promising that plans were made for a more extensive planting the following year. To facilitate planting, arrangements were made to have the site graded to eliminate the gulleys. Grading largely destroyed the 1964 planting, but evidence of the per­sistence of established Crownvetch was demonstrated by the sprouting of many crowns and rhizomes from the old planting during the 1965 growing season.

The planting was made May 21, 1965 with seeds and transplants in alternating vertical rows along the south-facing slope. Plants and seeds were grouped into three lots. Each lot of seeds and plants was planted in alternating rows of grass seed, 4 feet wide, and forbs 3 feet wide with the arrangement randomized for each class of material in the three replications. A second planting, of seeds only, was made adjoining the first. This consisted of vertical strips 4 feet wide, each strip repli­cated three times. Plants were set by trowel and seedings raked lightly to cover the seed. Fertilizer, 10-10-10, was applied to the site at a rate of about 400 pounds per acre at seeding time and again in 1966 and 1967.

A small trial planting of Dwarf Southern Wormwood, Arnold Dwarf Forsythia, Dwarf Bushhoneysuckle, Japanese Trailing Raspberry, and "Winona" Crownvetch was made for observation purposes on the south side of the road. Most of the balance of this highly erodible slope was sown to a mixture of Empire Birdsfoot Trefoil, Penngift Crownvetch, Timothy, Sideoats Grama, Flat Peavine, Sand Dropseed, and Switch­grass to prevent a recurrence of severe erosion.

The planting was first evaluated July 1, 1965 for germina­tion of seed and survival of the transplanted materials. Heav­iset germination noted was in Empire Birdsfoot Trefoil. Good germination was noted in Tall Wormwood and Penngift Crown­vetch. The poorest but still fairly satisfactory germination occurred in Chemung and "Winona" strains of Crownvetch. Flat Peavine failed to germinate satisfactorily.

Final evaluation was made in 1969 ( table 7). The poor performance of the following five species of

plants indigenous to the immediate area: Sweetfern, Dwarf Bushhoneysuckle, Lowbush Blueberry, Smooth Sumac, and Bristly Sarsaparilla requires some interpretation since this re­port emphasizes encouragment of the wider use of native plant species in the long range development for highway roadsides. The glacial till is of a very different structure and higher pH than that of the undisturbed surface soils of the area. All but sumac are plants adapted to acid soils. As weathering proceeds and a soil of more normal character for the area develops on this site, these species may find conditions more suitable.

Wendigo Slope, Community Park Plantings-1965

The planting site was located 7 miles southeast of Grand Rapids on County Highway 67, on a stony, rough slope with­out topsoil. It was a typical problem bank composed of coarse-textured glacial till. Both east and west facing slopes were used.

On May 21, 1965 plantings 10 feet wide and varying in lengt~ from 20 to 40 feet depending on position, were made runnmg the length of the slope. The seed was simply scattered and the gravel lightly raked to provide some seed cover. Plots were sown with Empire Birdsfoot Trefoil, Penngift Crown­vetch, Flat Peavine, and Sand Dropseed in three replications. Additional Empire Birdsfoot Trefoil was sown on other parts of the slope. A slope of lower profile across the road was also planted with Penngift Crownvetch, Empire Birdsfoot Trefoil and Flat Peavine. '

Germination, establishment, and growth of Birdsfoot Tre­foil was rapid. A good cover resulted during the first growing

32

Table 7. 1969 evaluation-Loon Lake plantings (plant­ed 1964 and 1965)

Plants

Tall Wormwood

Dwarf Southernwood

Japanese Trailing Raspberry

Bristly Sarsaparilla

Lowbush Blueberry

Arnold Dwarf Forsythia

Dwarf Bushhoneysuckle

Sweetfern

Smooth Sumac

Performance-1969

Fair. Suitable as temporary cover on light sandy soils.

Failure. Not adapted to soils of site.

Poor. Survived but lacks vigor un­der these soil conditions.

Adapted to light sands but has not transplanted easily. Performance poor to fair.

Failure. Gravel soil not suited for the acid soil plant.

Failure. Not adapted to soils of area and not sufficiently winter hardy for this location.

Failure. Not adapted to soil con­ditions.

Fair. Survival poor because of con­dition of planting stock.

Fair. Slow to take hold on this site.

Hughes Creeping Juniper Good.

Reynoutria Fleeceflower

Blue Creeping Juniper

Pirone Alfalfa

Sicklepod Alfalfa

Crownvetch

Birdsfoot Trefoil, Empire

Poor. Not adapted to the soil.

Very good. Well adapted to poor sandy soil.

Poor. Died out.

Excellent, vigorous. Needs closer planting to provide full cover, but worth further investigation.

All varieties good but germinati~n and establishment were best m Penngift followed by Emerald. Che­mung and "Winona" were about equally behind the first two var­ieties. Subsequent development has largely eliminated any differences between the varieties in soil cover­ing capability.

The most vigorous and most rapi~­ly establishing species tried on this site. It has spread freely over the whole planting area.

season. Crownvetch and Flat Peavine were comparatively slo~ in germinating and no significant cover developed in 19_6 from these species. In 1966 Birdsfoot Trefoil continued Jo give excellent and impressive ground cover. Birdsfoot Tref01l gr_ew freely over the slopes and into the rills and gulleys producmg a heavy mat of protective vegetation. Crownvetch and Flat

Pcavine were apparent in 1966, but very few plants of the latter species grew.

In 1967 Birdsfoot Trefoil still was the dominant ground cover. Penngift Crownvetch was beginning to cover the areas where it was planted. Flat Peavine was still present but not in sufficient quantity to be an effective ground cover.

On the basis of this trial, Empire Birdsfoot Trefoil is recommended for initial cover on bare slopes in this northern Minnesota area.

MORRIS STATION-1967

This was a two-part planting on a roadside near the Ex­periment Station. The first area included transplants while the second area consisted of replicated sowings of Penngift Crownvetch, Empire Birdsfoot Trefoil, Cicer Milkvetch, and Flat Peavine.

There has been an appreciable improvement in the quality of the Morris planting since it was fertilized heavily in 1967 and 1968 with complete 10-10-10 fertilizer at about 400 pounds per acre. Response has been especially good in Crown­wtch and Empire Birdsfoot Trefoil. Pirone Alfalfa and Car­sticn Alfalfa have completely disappeared. The performance of Dwarf Southernwood has not been impressive and plants have spread very little.

Satisfactory material on this site include the following: Empire Birdsfoot Trefoil (seeding) Penngift Crownvetch (seeding) Cicer Milkvetch (seeding) Flat Peavine (seeding) Crown vetch (crowns)

Unsatisfactory materials include the following: Pirone Alfalfa Carstien Alfalfa Reynoutria Fleeceflower Dwarf Southernwood

_Dwarf Southernwood performed poorly on this site. It was a. disappointment since it is tolerant of soils with a relatively high pH. The low fertility and dry soil of this roadside cut undoubtedly contributed to its failure.

CROOKSTON STATION-1965

Plant evaluation experiments were established in June 1965 on the Northwest Experiment Station at the University of Minnesota Technical College, Crookston, Minnesota. The plantings were established to determine winter hardiness and tolerance to the high pH soils (7.5-8.1) of the Red River Val­ley area. There has been no change in the relative ratings of the species since 1967.

Iron chlorosis, causing subsequent decline and ultimate death, is a serious physiological problem with many plant ma­terial~ grown in the high lime soils of the Red River Valley. Iron 1s ~ot available in sufficient quantity for plant growth under high lime conditions. Iron chlorosis has been observed on many of the species planted at Crookston ( table 8).

. C1cer Milkvetch, Goatsrue, and Pirone Alfalfa, which thnve u~der the soil conditions of the Crookston area, per­formed impressively. Crownvetch has grown quite well there, hut does. suffer from mild chlorosis, making it less attractive an_d po~s1bly shorter-lived than when grown on more suitable soils. C1cer Milkvetch performed well and is recommended for trial plantings on roadsides as a substitute for Crownvetch in a_lkaline soil areas. Goatsrue has a more upright and less de­sirable open growth habit than Cicer Milkvetch. A satisfactory cover f_ro~ Goatsrue may be obtained from heavy seedings.

. Qmcks1lver Petunia developed a spreading mat that was rtrernely effective in excluding annual weeds; it reseeded i recly and performed exceedingly well. Its annual nature Jim­ts Its usefulness to small scale planting or temporary cover.

33

Table 8. Iron chlorosis on potential ground cover plants grown at Crookston, Minnesota, 1967*

No chlorosis Mild chlorosis

Quicksilver Petunia Empire Birdsfoot Trefoil

Goatsrue

Cicer Milkvetch Pirone Alfalfa

Elliott Birdsfoot Trefoil

Smooth Sumac Dwarf Southern­

wood Germander

Speedwell Emerald Crownvetch Winona Crownvetch

Severe chlorosis

Dwarf Bush­honeysuckle

Bronx Forsythia Penngift Crownvetch

• Kalms St. Johnswort failed to establish from seed. Plants of Fringed Sage were dead by fall 1967.

Initial plantings of Pirone Alfalfa at the Landscape Ar­boretum and Horticultural Research Center created consider­able interest because of dense, low vigorous growth and over­all attractive appearance. The only success in other locations has been at the Crookston Station where it continues to rank among the best of the ground cover species. As with Cicer Milkvetch, there seems to be a marked ability to thrive on gumbo type alkaline soils. This species of alfalfa is not cur­rently available commercially; Seed for experimental plantings was obtained from the USDA Plant Introduction Station, Ames, Iowa. Further use or investigation of Pirone Alfalfa would require seed production from foundation material.

All Crownvetch varieties displayed some symptoms of chlorosis during the second growing season. The chlorosis however has not limited the quality of ground cover produced. The yellowish foliage is unattractive.

Germander Speedwell, a low plant of the Mint Family, which spreads by rhizomes under favorable soil and moisture, grew well only the first year.

This is the only planting in which the Birdsfoot Trefoils have not been rated with the best ground covers. Empire and "Elliott" strains displayed mild chlorosis on this site. Univer­sity of Minnesota legume specialists suggest that Birdsfoot Trefoil should grow well in open situations in the Red River Valley. Initially, Birdsfoot Trefoil may best be limited to trial plantings.

HIGHWAY SITE EVALUATIONS 1-494 HIGHWAY PLANTING-1963

In cooperation with personnel of the Minnesota Depart­ment of Highways, a site for planting ground covers was selected on Ossanna Hill, Station 189, 1-494 in Eden Prairie Township (figure 60).

The planting site was used for a greater variety of plant materials than any of the others used in this research project. The quality of the site was not an ideal one for the growth of plants but is characteristic of roadside conditions. The en­vironmental conditions for plant growth are minimal in terms of soil fertility and moisture. The west exposure of the slope further aggravates the harsh conditions present.

Excessively rainy weather delayed planting until June 21, 1963. Seedings were sown by hand in furrows, transplants were planted directly with a minimum of soil preparation. All plantings were replicated four times in plots 10 feet by 10 feet.

Transplanted materials were successful except for Reynou­tria Fleeceflower, which might have been too young and the division pieces too small to establish satisfactorily.

Performance Final Performance Final Class of 1 year after rating Reason if Class of 1 year after rating Reason if

Plant material planting 1969* unsatisfactory Plant material planting 1969* unsatisfactory

Arnold Dwarf plants 2 3 not fully Cutleaf Blackberry plants 2 not hardy Forsythia hardy or

aggressive Drophip Rose plants 3 died out

Rosendahl plants 3 3 poor cover Western Red plants died out Dewberry Raspberry

Carstien Alfalfa plants 3 3 unsatisfac-Snowberry plants poor stock tory growth

Sicklepod Alfalfa plants 2 3 died out Meadow Rose plants poor estab-lishment

Goatsrue plants 2 3 poor cover Max Graf Rose plants poor estab-lishment

Japanese Trailing plants 2 3 not Raspberry vigorous Pirone Alfalfa plants died out

Fringed Sage plants 2 3 not Georgia Bushhoney- plants poor estab-vigorous suckle lishment

Billiard Spirea plants 2 3 not Dwarf Bushhoney- plants poor estab-vigorous suckle lishment

Bayberry plants 3 3 died out Buckbrush plants poor estab-(W olfberry) lishment

Gold Drop Shrubby plants 4 poor Cinquefoil survival Creeping Mahonia plants 2 died out

Memorial Rose plants 2 not hardy Olympic St. plants 2 died out Johnswort

Silver Fleeceflower plants 2 not hardy Sweetfern plants failed to

Bronx Forsythia plants 2 not hardy grow

Chinese Wolfberry plants 3 poor cover Sicklepod Milkvetch seed 3 poor cover produced

Leadplant Amorpha seed did not es- Southern Bush- plants poor estab-tablish well honeysuckle lishment

Flat Peavine seed did not es- Prostrate Black plants 3 died out tablish well Locust

Thicket Creeper plants did not es- Wolfberry cuttings no eval- failed to tablish well uation root

Aaronsbeard St. plants 2 not hardy Georgia Bush- cuttings no eval- failed to Johnswort honeysuckle uation root

Chinese Wolfberry plants 3 poor Sweetfern root no eval- failed to growth cuttings uation root

Canada Milkvetch seed 3 poor estab- Southern Bush- cuttings no eval- failed to lishment honeysuckle uation root

Purple Four-leaf plants 1 poor Dwarf Bush- cuttings no eval- failed to Clover survival honeysuckle uation root

35

Performance Final Class of 1 year after rating Reason if

Plant material planting 1969* unsatisfactory

Goldflame Honey- cuttings no eval- failed to suckle uation root

Lilac Honeysuckle cuttings no eval- failed to uation root

Dwarf Bush- cuttings no eval- failed to honeysuckle uation root

Sweetfern root no eval- failed to cuttings uation root

Arctic Pfitzer plants no eval- died first Juniper uation season

Broadmoor Savin plants no eval- died first Juniper uation season

San Jose Creeping plants no eval died first Juniper uation season

Blue Rug Creeping plants no eval- died first Juniper uation season

TH-65 PLANTINGS-SODERVILLE, ANOKA COUNTY

This site was selected for evaluation of plant materials on sandy soils. The site, a 3: 1 cut located on the west side of TH 65, was characteristic of the infertile soils of the Anoka sand plain. Ten foot by ten foot plantings made on May 13, 1964 and April 23, 1965 were laid out in two tiers on the slope.

Plantings were watered at weekly intervals using a sprayer rig. To provide better watering facilities for newly transplant­ed materials, a sand point to which a portable shallow well pump could be attached was driven into the water table in May 1965. With this arrangement, more thorough and more frequent watering was possible.

All juniper varieties, Chemung Crownvetch and Bayberry performed well on this site ( table 10). Two raspberries, Ros­endahl and Japanese Trailing, survived moderately well but have not produced an effectively dense cover. Blueberry, S:,veetfern, Bristly Sarsaparilla, and Huckleberry did not sur­vive on the upper slope; however, adequate establishment was realized on the lower slope. Cowberry and Bearberry survived only on the more moist lower slope. Yucca did not produce adequate cover.

The relatively good performance of Crownvetch and Bay­berry on this site was not anticipated. Apparently once deep roots were established, these species were able to obtain ade­qu~te water despite dry surface conditions. Pocket gophers, eatmg the rather fleshy roots of the shrub, severely damaged the bayberry planting.

The difference in performance between the closely related Sweetfern_ and Bayberry undoubtedly reflects the quality of the plantmg _sto~k rather than the inherent potential for g'.o.~th on this site. Bayberry planted from root pieces and d1v1s10ns from old plants performed just as poorly as similar stock of Sweetfern. Well rooted nursery grown seedlings of Bayberry, however, adapted readily and grew well. Both Sweetfern and Bayberry are readily increased by division or

36

root cuttings in the nursery, but young plants require careful watering and cultural treatment difficult to provide under open field conditions.

Satisfactory plants on the Soderville, TH-65 site include two native selections of Cree.ping Juniper, Skandia Juniper, Chemung Crownvetch, Penng1ft Crownvetch, and Bayberry. Andorra Juniper, Tamarix Juniper, and Japanese Trailing Raspberry performed well but did not develop ground cover comparable to the preceding more highly rated species. The following plants failed or were unsatisfactory in quality of cover produced: Sweetfern, Lowbush Blueberry, Huckleberry, Dwarf Southernwood, Yucca, Cowberry, Olympic St. Johns­wort, Alaska Phlox, Bristly Sarsaparilla, Fringed Sage, Wine­leaf Cinquefoil, Silverweed, and Bearberry.

Wild Strawberry (Fragaria virginiana) although not planted on this site, has occupied a substantial area in the plantings. This native species is well adapted to sandy soils and bears some consideration as a ground cover where native plants are to be encouraged. The cover produced is not dense but may be adequate to protect the soil.

CLEVELAND AVENUE, ROSEVILLE, RAMSEY COUNTY DWARF SOUTHERNWOOD PLANTINGS

In April 1965, a large planting of Dwarf Southernwood, also known as Dwarf Sage or Dwarf Wormwood, was made on a steep west-facing bank on the interchange of I-35W and TH-36. Five thousand plants were planted in a staggered ar­rangement at 18 inch intervals on the site which measured 400 feet by 30 feet. At the time the slope carried a light cover of Smooth Bromegrass and some Kentucky Bluegrass.

Early work with Dwarf Southernwood had indicated con­siderable promise for its wider use and extensive trial as a highway ground cover. This plant grew rapidly and was read­ily increased by cuttings at almost any time of the year in the greenhouse. The plant has a pleasing gray-green color and the leaves persist into the winter months, presenting the effect of a nearly evergreen low shrub.

During summer 1965, plants were hoed periodically to re­duce weed competition. Fertilizer was applied at the time of planting and in 1967 and again in 1968.

Competition became severe enough to jeopardize the planting in 1967. In late May and again on July 24 the grasses were sprayed with an herbicide as a control measure. This freed the Dwarf Southernwood plants temporarily from com­petition. Herbicide control was repeated in 1968.

The overall performance of this planting is not satisfac­tory. It is irregular in appearance, partly from weed compe­tition but more from washing out and remedial sodding that was done during the first month after the planting was estab­lished. On the basis of the performance on this and other sites the previous recommendation of this species for large scale trial has been revised. Dwarf Southernwood is recommended for limited use on suitable soils where it can be maintained under cultivation until well established.

LAKEVILLE, 1-35 PLANTINGS-1967

Juniper Planting In spring 1967 a site was selected for experimental plant­

ings on a newly completed section of 1-35 in Lakeville To~n­ship, Dakota County near County Highway 70. An east f:icing exposure on fill approaching a bridge was selected. Jumpers, deciduous shrubs, and perennial materials were planted for evaluation as ground covers and of establishment procedures.

The juniper plants used in this study were balled and bur­lapped stock grown in the Arboretum nurseries ( table 11) · Plantings were made on May 12 and 15, 1967. Plants were spaced 3 feet apart in staggered rows and mulched with wood­chips to inhibit weed growth and conserve soil moisture.

Table 10. 1969 evaluation of materials planted in 1963 and 1964 on TH-65

Class of Initial Final Reason if Plant material performance rating* unsatisfactory

Creeping Juniper 2 year plants 1 1

Creeping Juniper 2 year plants 1 1

Creeping Juniper 2 year plants 1 1

Skandia Juniper 2 year plants 1 1

Chemung Crownvetch 2 year plants 1 1

Creeping Juniper 2 year plants 1 1

Japanese Trailing 1 year plants 3 2 thin cover produced on Raspberry this site

Andorra Juniper 2 year plants 2 2 hardiness not as satisfac-tory as in other creeping junipers

Yucca 1 year plants 2 2 cover too incomplete -decorative function only

Tamarix Juniper plants 2 2 good growth - hardiness somewhat questionable

Sweetfern ( spring dug) wild stock 3 3 proved difficult to estab-lish from wild dug plants

Blueberry 3 year seedlings 3 3 most died out on dry upper slopes

Fringed Sagebrush plants died out

Blueberry 2 year seedlings 3 poor establishment

Sweetfern (fall dug) wild stock 3 poor establishment

Oldfield Juniper 2 year plants failed to become estab-lished - poor planting stock

Wineleaf Cinquefoil plants failed to establish

Sweetfern wild stock failed to establish

Sweetfern wild stock failed to establish

Bristly Sarsaparilla wild stock failed to establish

Sweetfern root cuttings failed to grow

Huckleberry 2 year seedlings failed to establish

Olympic St. Johnswort 1 year plants not hardy

Dwarf Southernwood 1 year plants 3 not adapted to sand soil

• 1 = Excellent, 2 = Good, 3 = Poor.

37

Table 11. Performance of selected junipers after 2 years on the Lakeville site: planted 1967

Plant

Creeping Juniper Creeping Juniper Creeping Juniper Creeping Juniper Marshall Creeping Juniper Andorra Juniper Japanese Garden Juniper Pfitzer Juniper Blue Pfitzer Juniper Savin Juniper Tamarix Juniper Skandia Juniper

1969 Percent ground cover

30 20 20 60 50 40 80 60 60 55 60 75

1969 Rating*

2 2 2 1 1 3 1 2 2 2 2 1

• 1 = Excellent, 2 = Good, 3 = Po•,r.

Marshall Creeping Juniper is a vigorous bluish-green variety that produced a dense mat of vegetation. It is the best material in this planting and has performed well elsewhere.

Japanese Garden Juniper also performed well but did not grow as rapidly as the Marshall Creeping Juniper. It produced a dense blue-green foliage that covered the soil well.

The Skandia Juniper is a hardy form of Savin Juniper of low arching habit but does not have the free running habit of Creeping Juniper. This juniper was fully hardy exhibiting no winter injury.

Both Pfitzer and Blue Pfitzer Junipers are satisfactory plants for southern Minnesota in areas where exposure is not extreme. Plants grow into an arching shrub. Planted closely (3 to 4 feet) they produce a heavy cover.

Andorra Juniper is a juvenile form of Creeping Juniper with little tendency to spread. The juvenile foliage is more tender than that of varieties that develop mature foliage. The variety showed little tendency to creep in this plant­ing and exhibited winter injury. Savin Juniper and the Tama­rix variety of the same species were more prone to winter injury than the other species discussed above.

Legume Seedings Cicer Milkvetch, Sicklepod Milkvetch, Flat Peavine,

Schimid Lespedeza, Birdsfoot Trefoil, and Bird Vetch were planted May 12, 1967. Plantings were made in vertical strips in two tiers with three replications. The slope was prepared by raking. Inoculated seed was hand sown and the soil lightly raked to cover the seed. The seeded area was mulched with

Table 12. Germination and ground cover evaluation of herbaceous materials: planted 1967 at Lakeville

Plants

Birdsfoot Trefoil (Fridley) Birdsfoot Trefoil, Leo Birdsfoot Trefoil (SCS) Schimid Lespedeza Cicer Milkvetch Bird Vetch Flat Peavine

1967 Percent

germination

70 85 70 85 70

1969 Percent

ground cover

85 85 85 45 15

less than 10 less than 10

0 0

38

straw to conserve soil moisture and provide erosion protection to the slope ( table 12).

In table 12, only the Birdsfoot Trefoil varieties have estab­lished a satisfactory cover.

Deciduous Shrub Planting In autumn 1967 a planting of dormant deciduous shrubs

was made to observe performance under highway slope con­ditions. Single row vertical plantings of 12 plants each were made in four replications with plants spaced 3 feet apart in the row. Survival of the plants has been complete ( table 13).

Table 13. Performance of deciduous shrub plantings: planted 1967 at Lakeville

Plant

Dahurian Rose Kamchatka Rose Rose (unidentified) Georgia Bushhoneysuckle Cutleaf Stephanandra

• 1 = Excellent, 2 = Good, 3 = Poor.

1969 Rating•:•

2 1 3 2 2

The most effective plant in this group is the Kamchatka Rose. This is an extremely hardy (zone 2) rose from north­eastern Asia. The plants spread freely by suckering and reach a height of about 4 feet. The shrub flowered profusely.

The Dahurian Rose is similar in habit to the Kamchatka Rose but did not perform quite as well.

The unidentified rose species was grown from seed col­lected near Central City, Colorado. In the native location it produced an open thicket of stems about 3½ feet high. Its Minnesota growth was unsatisfactory and compared unfavor-ably with the above two species. .

Georgia Bushhoneysuckle is larger and grows m~re vigor­ously than the native Dwarf Bushhoneysuckle but 1s ~ot as hardy. There was evidence of winter injury on the f!latenal on this site although the species has performed well m the Ar-boretum for 10 years. .

Cutleaf Stephanandra is a low scr~mbling plan~ with branches that tend to strike toot when m contact with the soil. This material exhibited injury on exposed branch tips. On an exposed site it is possible more severe injury may occa­sionally be experienced, otherwise it would make an excellent ground cover.

NATIVE GROUND COVER COLLECTIONS

There are two native Minnesota junipers suitable for ground cover use: Prostrate or Oldfield Juniper and Creepmg Juniper. The native species of yew, Canada Yew (Taxus cana­densis), has a suitable shrubby habit but limited side adapta­bility and is quite unsuited to general roadside situations.

Both Prostrate and Creeping J unipcr are widely distri~uted in northern North America. Both species have given nse _to many improved cultivated varieties. In Minnesota both spe~i~s have statewide distribution except for the southwest pra_me area. On the premise that native plant materials are a logical source for fully adapted varieties, collections of plants. of bo

6t~

species in wild populations in the state were made m 19 and 1963.

Plant to plant differences are obvious when closely ob· served in the wild. Experience has demonstrated that these differences in habit, appearance, and structural. detail can be satisfactorily perpetuated by rooting cuttings. D1fferen~es due to habitat or accident of situation are not under genetic con·

trol and therefore are not reproducible in this manner. The seed reproduction of variants such as these is not acceptable because they do not reproduce true to type.

Extensive populations of native Creeping Juniper in Otter Tail and Polk counties were surveyed in October 1963. Col­lections were made by gathering cutting material from indi­vidual plants. Collection was determined on the basis of above average vigor, attractive appearance, or ground covering ca­pacity. Six collections were made in the vicinity of Paul Lake, Otter Tail County and 11 in southern Polk County on the dunes along the shoreline of glacial Lake Agassiz. Approxi­mately 50 cuttings were obtained from each selected plant. Cuttings were rooted in the greenhouse and transplanted to one of the project nurseries for observation and comparison.

The Prostrate or Oldfield Juniper of North America is considered to be a botanical variety of the Common Juniper of Eurasian distribution. Throughout its distribution range, the plant varies immensely in form from a prostrate shrub to an upright tree. Most North American forms are shrubby but differ strikingly on both a regional and individual basis. In Minnesota the plant is commonly a low shrub ranging up to 4 feet in height but individuals of low compact habit are frequently observed. Two such plants were collected in the East Bethel, Anoka County area.

Additional sources of variation in Prostrate Juniper were obtained from selections made in Massachusetts and of the Rocky Mountain form from near Central City, Colorado and the Black Hills of South Dakota. All accessions were propa­gated from cuttings grown in the Project 615 nursery for observation.

Numerous cultivated forms of both Creeping and Pros­trate Juniper are available in the nursery trade. Many of them were introduced into cultivation because of superior qualities of growth or habit as well as for sheer novelty of appearance. Obviously any new variety to be introduced must possess some quality not already marketed. Collections in this project have

been grown under nursery conditions for comparison with commercially available varieties and specimens grown in the Minnesota Landscape Arboretum.

Up to this time no Creeping Juniper selections have ex­ceeded the more vigorous cultivated clones such as Hughes or Marshall (table 14). Selection 63857, a male clone from Polk County has produced a good quality cover in the nursery: dense and weed free. Clone 63864 placed in a planting on sandy soil on the TH-65 planting site in Soderville, Anoka County has produced a satisfactory erosion protective cover. The plants are not obvious due to the presence of annual plants and weeds that grow through the rather open cover provided by the Juniper. In time as the plants thicken, it is anticipated that weed frequency will diminish and the Juniper cover will become more apparent. Other clones in the planting on l-35W in Lakeville, Dakota County have not been established long enough for evaluation. All clones of these selections require continued observation for some years be­fore their ultimate value can be determined. It is not possible to recommend any one of them now as being sufficiently su­perior to substitute for available recommended varieties of the Creeping Juniper.

The two local selections of Prostrate Juniper from East Bethel, Anoka County, 62880 and 62881, have shown desir­able qualities of vigor and habit of growth. Selection 62880 is somewhat lower and of better ground hugging character than 62881. Both are vigorous enough to be recommended for planting where a heavy juniper cover is desired. Planted at 3 foot spacings they developed a solid cover in 2-3 years.

No special advantage has been noted in Prostrate Juniper selection 65607 from Massachusetts. The Rocky Mountain forms under trial grew too slowly to be of value to this pro­gram but are exceedingly fine compact ornamental shrubs.

In neither of the above species is there a great tolerance for salt and in employing these plants, efforts must be made to place them so as to minimize chemical injury.

Table 14. Rating of Creeping Juniper collected from native stands after 2 years of growth: planted 1963

Number Diameter Performance Source plants Density* (centimeters) 1969

Native Ottertail County 56 4 40 Unsatisfactory Native Ottertail County 14 4 25 Unsatisfactory Native Ottertail County 28 4 27 Unsatisfactory Native Ottertail County 22 4 25 Unsatisfactory Native Ottertail County 21 4 25 Unsatisfactory Native Polk County 22 3 45 Borderline Native Polk County 7 3 40 Acceptable Native Polk County 11 1 50 Acceptable Native Polk County 4 2 45 Acceptable Native Polk County 2 1 50 Acceptable Native Polk County 19 2 40 Acceptable Native Polk County 3 3 40 Borderline Native Polk County 3 4 20 Unsatisfactory Native Polk County 7 3 40 Acceptable

• Density: 1 = Complete weed free cover; 2 = Sufficient cover and soil stabilization, some weed compe-tition; 3 = Borderline. Growth insufficient, weed competition; 4 = Unacceptable cover.

39

In 1963 a selection was made from an unusual Redosier Dogwood shrub growing in the University of Minnesota Ce­dar Creek Natural History Area in Anoka and Isanti counties. This shrub's branches were extremely fine and dense, quite unlike the coarsely textured open character of normal Redosier Dogwood plants. It apparently matures at about half the height of the normal plant. The plant lends itself well to low shrub plantings and may be particularly useful in areas with wet soils. The clone has been named 'Isanti' and is in the process of introduction to the horticultural trade.

Barrenstrawberry is a strawberry-like ground cover plant occurring sporadically in the northeastern United States and southern Canada. In Minnesota it occurs in Jack Pine areas of central St. Louis County. It is highly regarded as a ground cover because of its rapidly spreading manner of growth and its showy yellow flowers.

Material was collected near Biwabik, Minnesota and has been increased extensively in the Landscape Arboretum. It is included in the ground cover demonstration area. The plant has not exhibited as much drought tolerance as anticipated but is of vigorous growth and is worthy of further evaluation as a slope planting material.

Dwarf Pussy Willow is a low shrub willow of the prairie­oak savanna areas of Minnesota. Its low shrubby habit sug­gested its use as a low native ground cover. The plant matures at 2-3 feet. It is readily propagated by cuttings.

This low willow has grown well in preliminary trials but has not been outplanted in suitable test areas. It needs further evaluation.

EXPERIMENTS IN PROPAGATION AND ESTABLISHMENT

Crown vetch Crownvetch apparently was first planted in Minnesota

during the late 1920's or early 1930's. The oldest known es­tablished planting is still growing south of Winona on County Highway 74. This pfanting probably originated from seed sup­plied by the Soil Conservation Service ( SCS). Other SCS orig­in plantings were observed in Redwood County and in a U.S. Forest Service planting in Cass County. This was the most northerly location encountered during the early years of Proj­ect 615. During the last 5 years Crown vetch has become es­tablished throughout Minnesota.

Crownvetch has been widely promoted as an all-purpose "miracle" ground cover. Excellent and effective as it is when grown under proper conditions, the plant has a well grounded reputation for being difficult and slow to establish. From seed­ing time to full cover may require three or more growing seasons.

The long establishment time makes it necessary to plant a nurse crop for initial soil stabilization. Planting crowns (trans­planted pieces of plants or seedlings) may speed the process of developing a full cover under good cultural conditions.

To ensure proper plant growth, the root system of Crown­vetch must be inoculated with a specific rhizobial bacteria culture which is available commercially. New seedings of Crownvetch should be given 6-12-12 fertilizer at a rate of about 500 pounds per acre. Once established, Crownvetch ra~e)y requires supplemental fertilization. A pH of 5.5 is the mm1mum tolerated by Crownvetch while a range of 6.0 to 7.5 is optimal. When necessary, lime should be added to correct the pH.

_Three methods of establishment were investigated in ex­penn:ients under Minnesota conditions: ( 1 ) seeding directly in the f(eld, ( 2) plantiJ?g. ~reenhouse grown seedlings, and ( 3) planting crowns or d1v1s10ns.

Twenty-seven accessions were grown including the com­mercial varieties: Penngift, Chemung, Emerald, and "Cal­mar." Seed collected from the Winona stand was also included under the unofficial de5ignation "Winona."

An experiment using potted seedlings of Emerald, Che-

40

mung, Penngift and "Winona" was made at the Landscape Arboretum in April 1964. Seedlings were planted at 2 foot by 2 foot spacing in 10 foot by 10 foot blocks replicated three times.

Observation the first season confirmed the slow initial es­tablishment and growth of Crownvetch. Survival, however was complete. During summer 1965 the plants were accident'. ally mowed, which delayed evaluation until September 1966. Plants were scored for percentage of soil cover, average height of plants, relative vigor, and weed frequency (table 15).

In order of quality of cover, Chemung and "Winona" varieties formed the best cover followed closely by Penngift. Emerald did not develop adequate cover. Chemung and "Win­ona" were the tallest growing of the varieties. Penngift was consistently lower in height and finer textured than the other Crownvetch varieties.

Plantings with the most vigorous varieties had the fewest weeds. The very vigorous Chemung was especially competi­tive, maintaining a weed-clean planting area. The variety Em­erald was the least competitive resulting in weedy plantings.

Table 15. Mean ratings for establishment of transplant­ed seedlings of four Crownvetch varieties; planted May 25, 1967, and rated July 23, 1968

Percent Height Variety cover ( centimeters) Weedinesst

Emerald 43 45 "Winona" 58* 58 Chemung 55 48 Penngift 43 27

X 49 X 44 X s 7 s 12 s

• Indicates extremes beyond 1 standard deviation.

t Weediness rated 1 to 4, 1 = fewest weeds.

:j: Vigor rates 1 to 3, 1 = least vigorous.

3* 3 2* 3

3 X .4 s

Vigor:j:

1* 2 2 2

1 .17

Visually Chemung and "Winona" are very similar and _it is possible that the Chemung variety and the "Winona" strain arose from the same SCS stock.

A similar but more extensive planting was established from transplanted seedlings in 1967 along the north and south sides of a new road in the Landscape Arboretum. Perform­ance of the variety Emerald was more satisfactory in this planting. In addition to Chemung, Penngift, and "Winona" the trial included the Iowa strain known as "Calmar" and a USDA Plant Introduction Station selection from Kentucky. Variety plantings were replicated three times on each slope. Plots were 10 feet by 10 feet with plant spacing at 2 feet _by 2 feet staggered intervals. The cover produced in this planting was complete by July 1968 because of very favorable growmg conditions. There were very few weeds because of the com­plete cover. . ,,

The varieties Emerald, Chemung, Penngift, and "Winona were sown in replicated rod rows in a Landscape Arboretu~ nursery on June 1, 1964. Germination was somewhat erratic in the absence of irrigation, but a satisfactory stand was 0~­

tained with all varieties except Penngift. The autumn germi­nation noted in Penngift and Chemung was evidently ?~e to hard seeds finally responding to increased moisture. Ind1v1dual plants were measured for height and width at the end of the growing season ( table 16).

Table 16. Mean heights and widths of four varieties of Crownvetch after one growing season from seed: plant­ed June 1, 1964, scored October 7, 1964

Varieties

Chemung Emerald "Winona" Penngift

Seedlings

Mean Mean height width

(centimeters) (centimeters)

6.3* 32.5 10.3 35.7* 8.7 30.9 9.4 31.1

X = 8.7 X= 32.6 s 1.7 s = 2.24

Indicates extremes beyond 1 standard deviation.

Chemung was markedly lower in height growth in this trial while Emerald was somewhat better in its spreading ability than the other three varieties ( table 17). Analysis of variance indicated no significant difference among varieties in respect to height or spread.

Another comparative seeding of varieties was established May 9, 1967 with the varieties Emerald, Chemung, "Winona," Penngift and two accessions of "Kentucky" in replicated nur­sery rows. On July 23, 1968, plantings were measured and the average height and width of each determined.

The comparative performance of all varieties in this plant­ing was uniformly good. The plantings were scored for aver­age height and overall performance. Height does not neces­saily indicate any inherent superiority in taller scoring varie­ties. The scoring for overall performance is probably a more meaningful measure for ground cover purposes ( table 17).

Table 17. Ratings of Crownvetch seedlings grown on the Landscape Arboretum slope: planted April 28, 1964, scored September 11, 1966

Varieties

Emerald Chemung Iowa ("Calmar")

"Kentucky" "Kentucky" "Winona" Penngift

Seedlings

Mean height Performance• (centimeters) rating

X s

50.0 49.16 49.16 50.0 45.8 47.5 45.0 48.09

2.02 X s

l.6t 1.8 1.8 1.6 2.0 2.1 t 2.0

1.9 .186

' Performance rating = 1. excellent, 2. good, 3. fair. t Indicates extremes beyond 1 standard deviation.

. While Emerald and one lot of "Kentucky" scored highest m_ over~ll performance, it should again be emphasized that this entire planting developed so well that varietal differences Were difficult to observe.

Direct seeding of Crownvetch varieties in comparative

41

plantings gave results similar to those reported in table 17 for transplanted seedlings. In the nursery trials, however, it was possible to observe the spreading capability of individual plants, which is a property of more significance in ground covers than is height ( table 18). The entire planting was in such excellent condition that no judgment of variation in vigor was practical (fig. 61).

Table 18. Mean heights and widths of five Crownvetch varieties grown from seedings: planted May 9, 1967, scored July 23, 1968

Seedlings Height Width

Varieties (centimeters) (centimeters)

Emerald "Winona" Chemung Penngift "Kentucky"

X s

53.33 * 45.00 50.00 40.00* 43.33 46.33

5.32

• Departure beyond 1 standard deviation.

X s

131.66* 110.00* 120.00 123.33 130.00 122.98

8.67

Emerald performed especially well in terms of spread in this trial while "Winona" was the poorest of the varieties.

Direct Seeding of Woody Plants

Sumac Seed Experiments In Minnesota, both Smooth and Staghorn Sumac frequent­

ly invade highway slopes. They have been regarded as a mixed blessing, a nuisance on slopes that were mowed regu­larly but sometimes tolerated on long unmowed grades. Sumac has often been the object of herbicidal sprays where mainten­ance has concentrated on the elimination of woody plants. The attractive summer foliage and striking autumn coloring adds to the landscape value of these plants. In winter the red fruiting "bobs" or seed heads borne on the bold open branch­ing structure add to sumacs' landscape appeal.

Smooth Sumac Smooth Sumac ranges widely over the United States and

southern Canada. It tolerates a relatively broad range of pH and can thrive on subsoils as well as normal topsoils. It is commonly seen on hot dry south-facing slopes where many other woody species find it difficult to become established. However, it favors no particular exposure. Smooth Sumac spreads vegetatively by rhizomes and single plants can even­tually occupy a large area. Colonies or clones, each derived from one original seedling, are readily discernible to the trained observer who can detect the likeness of individual stems within a given colony.

Experiments were designed to investigate some of the re­quirements associated with germination and establishment of Sumac. Investigations were limited to Smooth Sumac because its lesser height at maturity makes it more desirable for slope plantings than the larger Staghorn Sumac. Treatments in­cluded boiling water, hot water (150° F.), sulfuric acid soak, mechanical scarification, and stratification, Under the experi­mental conditions, boiling water was found to be a safe, read­ily controllable, inexpensive method of seed pretreatment ( Johnson et al., 1966). Further investigation will be required before any of the treatments can be recommended on a prac­ticable basis.

Direct Seeding of Smooth Sumac To determine the effects of planting time and seed pre­

treatment on the establishment of Smooth Sumac, a study was designed incorporating untreated seed and seed -'?retreated with boiling water to break down the_ seed coat re~1stance to water imbibition. The procedure consisted of plantmg treated and untreated seeds, 5 seeds per hill respectively in hil}s 2 feet apart with 20 hills per line at ap~ro~imatel)'. weekly mtervals beginning October 28, 1966 contmumg until freeze-up (No­vember 23, 1966) and resuming March 28, 1967. The last of 15 plantings was made on June 5, 1967.

A steep west facing slope was selected on 1-494 near the County Road 60 interchange in Eden Prairie. The slope had a cover of Smooth Bromegrass, Sweet Clover, and Leafy Spurge. . . · f

Periodic checks were made in 1967 for germmat10n o fall and spring sown seeds. Competition w!th the e_xisting vege­tation caused the death of the few seedlmgs which had ger­minated as soon as dry summer weather set in. There was no survival the first year so that no conclusions could be drawn as to the effectiveness of pretreatment with boiling water.

Further checks which occurred periodically until 1969 in­dicated no further germination. This method for ~stablishing sumac on roadsides evidently is of no value, especially where there is grass competition.

Hydroseeding of Smooth Sumac Seed An experimental Smooth Sumac seeding using the Highway

Department's hydroseeder was undertaken ?~ April 14, 1966, on the Ossanna Hill cut on 1-494, Eden Prame.

Nineteen pounds of Smooth Sumac collected locally were pretreated by immersion in boiling water. The seed was '.1dded to 1,300 gallons of water in the hydroseeder and apphed to an area approximately 90 feet by 400 feet on the lower part of the east facing slope. Based on 68,600 seeds per pound, an estimated 1,300,000 seeds were applied to the area. Germ_ina­tion tests showed 73 percent live seeded which resulted m a seeding rate of approximately 26 live seeds per square foot. The seed was not covered or mulched, the soil being rough enough at the time of seeding to provide some covering as a result of washing.

The first observations were made on April 19, 1966 using a quadrat of 1 square foot randomly situated in the seeded area. These observations indicated an average of 7.5 exposed seeds per square foot, which would account for about one fourth of the seeds discharged into the plot. Germination was poorer than expected. No seedlings were observed during 1966. It was not until 2 years later that seedlings of Smooth Sumac began to appear in and immediately around the hydro­seeded plot. While both Smooth and Staghorn Sumac are ap­pearing sporadically around the Ossanna Hill cut, the concen­tration of plants in the hydroseeded areas is an indication of significant establishment as a result of this seeding.

Chances of success and valid evaluation of the seeding are very limited because this area has been mowed annually. This has prevented the sumac seedlings from developing and con­tributing to the effective cover on the slope.

Direct Seeding of Woody Ground Covers-Cannon Falls Direct seeding of woody plants offers a tempting approach

to cost reduction in establishing stands of such materials. The high cost of nursery stock, high planting and maintenance costs combine to make the establishment of plantings expen­sive. If plantings could be satisfactorily established by seeding, costs would be cut.

Most research in the area of woody plant establishment by direct seeding has been done with forest trees. With the ex­ception of the southern pines, and moderate success with Jack Pine, little significant success has been achieved in direct seed-

• A product manufactured by Conwed Co., Cloquet, Minnesota.

42

ing of forest trees and s~rubs. Properl_y treated _seed of g?od quality will usually germinate but survival and final estabhsh­ment of the seedings is often too low to be of value in re­vegetating bare sites. Under natural conditions seeding usually takes place at an extraordinarily high rate. Germination may be good but losses are correspo_ndingly ?igh_ and the ultimate population reaches a balance with the s1tuat1on.

The purpose of this experiment was to determine the prac­ticability of employing direct seeding procedures for the es­tablishment of woody ground cover plants on steep slopes. A comparison was also made of seed treat~ent and mulching materials in the germination and establishment of woody ground covers.

The experiment included twelve kinds o~ seed treatments and was laid out on the east and west facing slopes of the Cannon Falls bypass ( table 19). Plantings were done in three tiers on each side of the road with _seed lots randomized in each tier. Planting dates were May 20, 1965 for the west bank and June 9 1965 for the east bank. The late planting dates on this dry, sandy location undoubtedly contributed to the poor results.

Table 19. Cannon Falls direct seeding test: plant and mulch materials used

Plant materials Mulch materials

Smooth Sumac (untreated) Smooth Sumac (stratified) Smooth Sumac (acid treated) Autumnolive Partridgepea Fragrant Sumac Bayberry Buckbrush Sea Buckthorn Virginia Creeper

Straw Wood Pulp Wood Chips

Both untreated and pretreated seed were used in t~is e~­periment. Pretreatment of seeds consisted of a sulfuric acid soak of the hard seed coats of Smooth Sumac to bre~~ down the resistance to water imbibition. All seeds were st~at1f1ed for 60 days prior to sowing with the exception ?f Partndgepe~.

Individual plots were 20 feet by 6 feet wit~ ~ 4 fC?ot b01 der between plots. After sowing, the plots _we~e. d1v1ded ~nto three equal subplots, which were mulched _in~1v1~ually with straw, wood chips, and wood fiber.* The d1stnbut10n of the mulch material was randomized throughout the subplots.

Best germination with Partridgepea resulted under t~e wood fiber, while the poorest was obtained under. straw m eight of the nine plots. In the top tier of the east facing slope, the wood chip treatment produced slightly more seedlings than wood fiber when scored on July 31, 1965. . ,

Untreated Smooth Sumac Buckbrush, Autumnohve, Ba)· berry, or Sea Buckthorn failed to germinate. Germination was observed in acid treated and stratified Smooth Suma~, Frag­rant Sumac, and Virginia Creeper. As ~ith the Part1dgepea, germination was best under the woo~ fiber. mul~h follC?wed closely by wood chips. Straw was decidedly mfenor to e1!her wood fiber or wood chips in most plots. Up to 400 seedl~ngs of Smooth Sumac were observed in one of the wood fiber subplots. Mortality was heavy and could be attri_bute~ to the draughty nature of the sandy soil. When examined (n Sep­tember 1965, Smooth Sumac in small numbers survived. 10

only seven plots in the lower two tiers of the east fac!ng slope. Seedlings in the top tier and all th?st: ~n the west ~aci~! slope had perished. The two plots of VIrginia Creeper m t

two lower tiers of the east facing slope contained a few seed­lings at this time but ultimately perished.

The failure of this planting may be partially attributed to the late planting dates and the sandy soil with little water hold­ing capacity. Under these site conditions, planting may have been more successful in late April, which would have allowed germination during cooler weather when moisture was still abundantly available.

PLANT SURVEYS OF EXISTING HIGHWAY SLOPES

One objective of the research program was to determine what plant species were present on roadsides, the relative im­portance of various species and how their presence might be related to maintenance practices, past and present. To obtain this information, vegetation composition surveys were made on selected highway slopes in south central Minnesota.

On the sites investigated the proportion of native (i.e., in­digenous species) plants on roadsides was found to depend on the age of the slope. On the older relatively undisturbed slopes the native species ranged up to 90 percent of those present while on newly established slopes they might run as low as 10 percent, the latter being primarily native weedy plants such as ragweeds.

The native materials found on the older sites were mostly Jong-lived perennials, a situation brought about by manage­ment which has largely excluded woody species.

The native materials are in large part components of the original prairie vegetation of the state. Sound management aimed at encouraging such native flora can produce stable, attractive roadsides requiring minimal maintenance.

ADDITIONAL RESEARCH CONSIDERATIONS

The primary effort of the program was focused on the evaluation of plant materials for highway planting. A limited amount of work applied to the propagation and cultural re­quirements of each species. As a result, much remains to be learned about the detailed requirements of many of the lesser known species and varieties included in this report.

Information on the propagation and establishment of plants adapted to acid soils is needed to broaden the numbers and use of plant materials in acid situations. Bayberry, one of the finest ground covers for sandy soils, is difficult to trans-

plant, indicating a need for selection of plants which root with greater ease and grow vigorously.

Sweetfern is a plant worthy of serious investigation in propagation and establishment in highway planting. With spe­cial care, Sweetfern can be propagated by root cuttings. Young plants must be grown as nursery stock before trans­planting to the field.

Junipers comprise the only coniferous evergreen group adapted to ground cover use in northern situations. It is pos­sible that more research on forms and hardiness in this group could result in the production of new forms and clones with adaptive qualities, An example may be taken from the Skandia Juniper, a hardy form of the Savin Juniper. The common Savin Juniper originated in central Europe and is not hardy.

Development of similar variations may be possible in other species if research were undertaken. With the exception of Japanese Shore Juniper, most junipers are not very salt toler­ant. The Japanese Shore Juniper, though salt tolerant, is not hardy in Minnesota. The possibility of combining the two characteristics depends on further research.

MISCELLANEOUS SMALL TREES BROUGHT INTO THE PROGRAM

As a result of the broad interest in plant materials suited to highway use some nonground cover type plants inevitably found their way into the program. These are of interest and value but not to be equated with the ground cover species.

Autumnolive is a small tree related to the commonly planted ornamental Russianolive. The plant has merit for planting on dry alkaline soils but none of the accessions re­ceived in this program proved to be sufficiently winter hardy in Minnesota (table 20).

Sea Buckthorn, another plant related to Russianolive, is fully hardy and may be used interchangeably with Russian­olive throughout southern Minnesota. Like Russianolive, the Sea Buckthorn is a small tree suited to dry and alkaline soils. It is well adapted to use for screening, its silvery white foliage providing a striking visual effect during the summer months. Fruits from low-growing nearly prostrate forms of American Plum and Western Chokecherry were collected near Boulder, Colorado. These materials were grown to determine if their low habit was sufficiently heritable to make these forms useful as seed grown varieties for possible bank planting. Plants have not been observed sufficiently long to judge their potential value.

Table 20. Evaluation of small trees for. roadside planting

Hardiness Plant Plant zone Height type Evaluation and comments

Autumn olive 5 10' shrub Tolerates alkaline and salt (Elaeagnus umbellata) soils. Not sufficiently hardy

in Minnesota. Sea Buckthorn 3 10' shrub Tolerates alkaline and salt (Hippophae rhamnoides) or small soils. Suitable for screening

tree and background plantings on difficult sites.

American Plum 3 4' shrub A low-growing variant not (Prunus americana) adequately evaluated. Western Chokecherry 3 5' shrub A low-growing variant not (Prunus virginiana var. adequately evaluated. demissa) Siberian Salttree 2 6' woody Extremely hardy, salt toler-(Halimodendron ant shrub adapted to saline or halodendron) alkaline soils. Circumneutral

to saline soils, full sun. Estab-lish by transplants.

43

Ill. Establishment and Maintenance of Plant Materials

This section gives a brief summary of plantings and selec­tion considerations. A trained landscape manager should evaluate individual situations, select plant materials, and over­see maintenance operations.

GRADES AND STANDARDS

Seed Seed should be certified for purity, germination, and al­

lowable weed seed content. Proper bacterial inoculant should be specified for legume seed.

Plant Materials All plant materials should be selected and specified ac­

cording to "USDA Standard for Nursery Stock" (196~). Woody plants are ordinarily marketed as: (1) bare root, 1.e. without a soil ball around the roots; (2) balled and burlapped (B & B), i.e. with a soil ball around the roots and (3) as con­tainer-grown or potted stock.

Bare root stock is commonly dug in the fall and stored over-winter for spring sale and planting. B & B stock is usually dug in either spring or fall for immediate planting._ Contai~er or potted stock may be field planted at almost any time durmg the growing season.

All plant materials should be specified b}'. spe~ies and variety, size and/or age, and manner of handlmg; 1.e., bare root; B & B; or container-grown. Evergreens sh~uld never be specified as bare root. Liners ( small rooted cuttmgs) are de­signed for nursery trade and are not recommended.

The smallest size of finished, spreading type juniper nur­sery stock is generally offered as 15-to-18-inch spread in varie­ties such as Skandia or Pfitzer Juniper. Sizes offered may range up to 3 or 4 feet. The unit cost of larger sizes increases rapidly. In general the smaller sizes will prove more economi­cal if adequate post planting care is provided. Larger sizes can be justified for quicker landscaping effect but are likely to have a higher mortality during the establishment period than smaller stock.

SOURCE OF PLANT MATERIALS

Local purchase of plant materials is recommended when­ever possible. Usually there are advantages to obtaining nur­sery stock locally. This ensures local adaptation of the ma­terials where hardiness differences exist within a species. Local acquisition is particularly important for collected materials and materials grown from seed.

Clonal material, which includes most evergreens, can be grown at distant locations. However, local production en­sures proper hardening or conditioning of a plant to the sea­sonal stresses of Minnesota's climate.

HANDLING OF PLANT MATERIALS

Seed Seed should be planted immediately or stored in a cool dry

place in a rodent proof container. Seed should never be al­lowed to become moist in storage.

Plants Bare root materials (decidious) Bare root stock should be planted immediately after pur­

chase or removal from storage. It must be stored under cool moist conditions. Roots must be protected and kept moist at all times during storage, transport, and planting. Damaged roots and branches should be pruned before planting.

Container-grown materials (decidious and evergreen) Container-grown and potted plant materials can be planted

almost any time during the growing season. Metal and durable

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containers should be removed prior to planting. Pressed peat containers should have the bottom removed and the top of the container removed to the soil line. The soil ball in containers and at the time of planting should be continually maintained in a moist condition.

Balled and Burlapped Materials (evergreens)

The B & B technique is used primarily with field grown evergreens. Care must be taken to lift only the ball and not the stems or trunk. Rough handling of the soil ball results in destruction of the root system and separation of roots and soil. If B & B stock is not planted immediately it should mulched and maintained in a moist condition.

PLANTING

A soil test is recommended to determine a fertility pro­gram for each planting site. Instructions and containers for soil testing are available from county agents throughout the state. Samples may be mailed directly to the Soil Testing Lab­oratory, Department of Soil Science, University of Minnesota, St. Paul, Minn. 55101.

Topsoil should be spread to a depth of 4 to 8 inches. Till­ing and mixing of the _first 2-3 inches ~~ topsoil with the ~ub­soil bonds the two soil layers and facilitates water, nutnent, and root penetration. This practice also reduc~s the possibility of slides and slips after plants become estabhshed. If no soil test is available, tilling in 0-20-0 or 0-20-20 fertilizer to a depth of 5-6 inches at the rate ?~ 800 pounds per . acre is recommended. Nitrogen (N) fertlhzers are best applied and lightly incorporated into the surface of the soil. Readily avail­able N should be applied at a rate of ½ pound actual N per 1,000 square feet or at one-half the rate o_f potassi~m and phosphorus. When _wood chip or other org~~1c mulch 1s used, a periodic topdressmg of 10-10-10 type fert1hzer at the rate of 1 pound N per 1,000 square feet is advised. In acid soils, li~e should be applied and tilled into the topsoil prior to plantmg according to soil test recommendations.

Topsoils used in planting hol~s for b~e root, B & B,_ ~nd container material should be ennched with 0-20-20 fertilizer at the rate of 2-3 pounds per cubic yard of soil. In shrub planting areas, 3-4 pounds of 0-20-20 tilled into 100 square feet of area is recommended.

Seeding Topsoil should be tilled and graded pri~r to see_din_g. S_eed

should be broadcast or drilled to ensure uniform d1stnbut10n. Drilling ordinarily results in a light soil covering over the seed. Broadcast seedings should be covered lightly _by me~ns of a light drag or raking. Seedings must be kept m01st contmuously after the seeds have started to germinate until seedlings are well established ( 3-4 weeks).

Early spring and fall seedings generally give the best ~e­sults. Mulching with straw at 1 ½-2 tons per acre tacked with asphalt has proven to be very beneficial and is recommended on all seedings.

PLANTING OF NURSERY STOCK

All nursery stock can be planted as purchased. Holes should be deep enough to ensure planting at the same dep!h as the plants were in the nursery. Plants should be planted m staggered rows across a slope. Planting distances should be determined by the type and size of plant material used _(some plants spread more and faster than others), by the kmd_ of effect desired (e.g., a mass effect planting) and the time needed to develop full cover. .

The soil around plants should be secured firmly aft~r planting. Plants should be watered immediately to settle so~ and then mulched with a long lasting material such as woo chips to conserve moisture.

When B & B or container grown plants are used, the ~ole should be at least 6 inches larger than the ball. The subsoil at

the bottom of the hole should be loosened at the time of planting. The burlap on B & B materials should be cut in sev­eral places at planting time. Enriched topsoil should be eased in gradually and firmed around the base. A depression should be left around the plant when finished in order to hold water. Plantings should be watered immediately and then mulched.

ESTABLISHMENT OF PLANT MATERIALS

The control of weeds, particularly during the establish­ment period, is important to the welfare and appearance of a planting. Weed control can be accomplished mechanically through cultivation or chemically. Where weed conditions warrant, pretreatment of the planting site with short-lived sterilants such as methyl bromide or Vapam may be desirable.

In seeding a legume such as Birdsfoot Trefoil a mixture of 1 pound dalapon and ½ pound 4-(2,4-DB) per acre controls grassy and broadleaf weeds.

Dacthat• is an herbicide commonly used on ornamental plants. It controls certain annual grasses and broadleaf weeds. Rates suggested are 15-20 pounds in 50 gallons of water per acre, which can be applied 2 days after transplanting! It is best used in spring as a pre-emergence herbicide. Treflan (triflura­lin) may be used similarly for broadleaf weed and annual grass control at 1 pint (light soil) to 1 quart (heavy soil) per acre on preplanted stock. Treflan must be incorporated into the soil after application. Princep SOW ( simazine) can be used on coniferous plantings at 2-4 pounds per acre as a pre­emergent weed control.

MAINTENANCE OF PLANT MATERIALS

Maintenance should be minimal after ground covers have been established ( see list of Recommended Varieties, page .. for suggestions for individual ground covers).

Most woody plants will require a periodic top dressing of fertilizer. Deciduous materials may be fertilized with a 1-2-2 ratio fertilizer at the rate of ½-1 pound of actual N per 1,000 square feet. Evergreen materials should be fertilized with a 2-1-1 or 1-1-1 ratio fertilizer at the same rate during the spring of the year. Fertilization should take place prior to June 1.

Weed control may also be desirable in some plantings dur­ing the establishment period. The same materials recommend­ed above may be considered.

Woody plantings should be designed so that mowing around individual plants is unnecessary. Mulching and herbi­cide use can serve that purpose. Some legumes may spread beyond the designated planting area and these may !le con-

trolled by mowing. An occasional mowing of the entire plant­ing will not injure such legumes as Birdsfoot Trefoil. Crown­vetch, however, will be permanently injured by mowing. Dwarf Southernwood and certain other species mentioned in Recommended Varieties can be mowed with the mower set at the highest level.

Care should be exercised with the use of 2,4-D type chem­icals around all legume and woody plantings. These chemicals can kill or severly injure nongrassy plantings under common application rates.

AVAILABILITY OF PLANT MATERIALS

Many plant materials recommended in this report are not commonly available from commercial nurseries. Some ma­terials are available in limited numbers from nurseries located in Minnesota and other states.

It may be necessary to contract production of certain ma­terials until they become established in the nursery trade. The Minnesota Nurserymen's Association will supply names of producers interested in contract production. A supply of basic propagation stock would have to be made available at the ini­tiation of production. Special arrangements would be required with the University of Minnesota for furnishing propagation stock.

Most of the recommended materials in limited produc­tion could be readily propagated in large numbers once a demand was established. Materials falling into this category are in the cinquefoils, Dwarf Southernwood, Reynoutria Fleeceflower, etc.

Many plant species are naturalized over a wide range of climatic conditions. In certain areas locally adapted races have developed. The locally adapted race may have the same ap­pearance as a hardier type from another area. With this in mind, qualified plantsmen should be consulted before pur­chasing plant materials produced in states other than Minne­sota.

List of References American Association of Nurserymen. 1969. U.S.A. Standard

for nursery stock. USAS 260.1. 27 pp. Johnson, A. G., L. E. Foote, and M. H. Smithberg. 1966.

"Smooth sumac seed germination." Plant Propagator 12 (3):5-8.

Kelsey, H. P. and W. A. Dayton, editors. 1942. Standardized plant names. J. Horace McFarland Co., Harrisburg, Penna. 675 pp.

'The inclusion of a trade name does not imply endorsement by the University of Minnesota and exclusion does not imply nonapprovai. 'Reprinted by permission; Farm Technology, Vol. 25 (3), 1969.

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Figure 2. Bearberry

Figure 3. Crownvetch

Figure 4. Tawny Daylily

Figure 5. Redosier Dogwood

Figure 6. Arcadia Juniper

Figure 7. Skandia Juniper

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Figure 8. Creeping Juniper

Figure 9. Japanese Garden Juniper

Figure 10. Oldfield or Prostrate Juniper

Figure 11. Pfitzer Juniper

Figure 12. Sargent Juniper

Figure 13. Cicer Milkvetch

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Figure 14. Kamchatka Rose

Figure 15. Fragrant Sumac

Figure 16. Smooth Sumac

Figure 17. Birdsfoot Trefoil

Figure 18. Prostrate Alfalfa

Figure 19. Pirone Alfalfa

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Figure 20. Sicklepod Alfalfa

Figure 21. Barrenstrawberry

Figure 22. Bayberry

Figure 23. Allegheny Blackberry

Figure 24. Georgia Bushhoneysuckle

Figure 25. Dwarf Spring Cinquefoil

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Figure 27. Friedrichseni Cinquefoil

Figure 28. Irving Cinquefoil

Figure 29. White Clover

Figure 30. Zigzag Clover

Figure 31. Cowberry

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Figure 32. Thicket Creeper

Figure 33. Virginia Creeper

Figure 34. Reynoutria Fleeceflower

Figure 35. Lilac Honeysuckle

Figure 36. Rush Lespedeza

Figure 37. Sicklepod Milkvetch

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Figure 38. India Mockstrawberry

Figure 39. Partridgepea

Figure 40. Russian Peashrub

Figure 41. Perennial Peavine

Figure 42. Herbaceous Periwinkle

Figure 43. Quicksilver Petunia

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Figure 44. Alaska Phlox

Figure 45. Maiden Pink

Figure 46. Magic Carpet Polygonum

Figure 47. Japanese Trailing Raspberry

Figure 48. Fringed Sage

Figure 49. Common Snowberry

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Figure 50. Dwarf Southernwood

Figure 51. Billia rd Spirea

Figure 52. Dwarf Garland Spirea

Figure 54. Two-row Stonecrop

Figure 55. Sweetfern

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Table 3. Plants not recommended or not sufficiently evaluated for Minnesota roadsides (continued)

Plant Plant Evaluation, comments, and Name zone height Type availability

PEAVINE, GROUNDNUT 3 3' vine Not as strong growing as Flat Pea-(Lathyrus tuberosus) vine. May be toxic to cattle.

PEA VINE, PERENNIAL 3 3' vine Herbaceous ground cover. Does (Lathyrus sativus) not produce adequate cover.

PINE, BROOMED JACK 2 5' woody D\•:a:f co~pact shrubby evergreen. (Pinus banksiana "Broom") Ac1d1c to circumneutral soils, full

sun.

PLANTAINLILY 4 1' herb* Rare possibility of use in shady (Hosta sp.) sites. Part or total shade.

RASPBERRY, WESTERN RED 3 2' woody Western form of common rasp-(Rubus idaeus aculeatissimus) berry.

ROSE, DAHURIAN 2 4' spreading Promising rapidly spreading shrub (Rosa davurica) shrub rose suited to most well-drained

soils. Insufficient evaluation.

i\ ROSE, DROPHIP 5 4' woody Not hardy in Minnesota. (Rosa pendulina)

ROSE, MAX GRAF 5 3' trailing Not fully hardy in Minnesota.

~ (Rosa 'Max Graf') woody

5 2' half ever- Hardy only in southern Minnesota. ROSE, MEMORIAL (Rosa wich11raiana) green Trailing stems.

shrub

SAGE, JERUSALEM 4 3' herb* Insufficient evaluation. Coarse-tex-

(Phlomis tuberosa) tured plant; spreads by suckering.

ST. JOHNSWORT, AARONSBEARD 5 1' herb"' Not hardy in Minnesota.

(Hypericum calycinum)

II Classified as noxious weed. ST. JOHNSWORT, COMMON 4 1½' herb* (Hypericum perforatum)

ST. JOHNSWORT, HIDCOTE 6 2' woody Not hardy in Minnesota.

(Hypericum patulum 'Hidcote')

ST. JOHNSWORT, KALM 3 3' woody Shrub difficult to establish. Hardy in Minnesota. Acid to circumneu-

(Hypericum kalmianum) tral soils, full sun or part shade. Establish from transplants. Avail-ablity limited.

ST. JOHNSWORT, OLYMPIC 5 6" subshrub Not hardy in Minnesota

(Hypericum olympicum)

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Figure 56. Bird Vetch Figure 59. Adamsneedle Yucca

Figure 60. 1963 plantings on 1-494

Figure 61. Crownvetch plantings in Landscape Arboretum

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