Selecting and Growing

AcknowledgmentAppreciation is expressed to Dr. Frank Bryan, Albert Penland and James Thornton, members

of the Oconee Chapter of the Azalea Society of America, for their assistance with this publication aswell as a corresponding PowerPoint presentation.

Acknowledgment is also made to Dr. Frank Bryan, Richard Clapp, Allison Fuqua and JamesThornton for providing many of the photos within the publication. Last, but certainly not least, sincereappreciation is expressed to Sharlys Crissafulli, Program Assistant in the Department of Horticulture,for her tireless efforts in editing and formatting this publication.

Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Grouping Azaleas by Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Evergreen vs. Deciduous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Flower Forms and Petal Shapes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Time of Bloom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Native vs. Introduced Cultivars and Hybrids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Considerations When Selecting Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Cold Hardiness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Flowering Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Mature Plant Size and Flower Color . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Plant Health . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Your Landscape Needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Planting Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Site Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Planting Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Mulching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Watering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Fertilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Pruning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Common Azalea Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Cultural and Environmental Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Insects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Propagation of Azaleas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Suggested References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

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Selecting and Growing AzaleasGary L. Wade, Ph.D., Extension Horticulturist

S. Kristine Braman, Ph.D. EntomologistJean Williams Woodward, Ph.D., Extension Plant Pathologist

The University of Georgia

in cooperation withFrank Bryan, Ph.D., Jim Thornton and Albert Penland,

Oconee Chapter, Azalea Society of America

IntroductionFew plants can rival the spectacular floral dis-

plays of azaleas. Their vivid colors, profusion offlowers, and adaptability to a wide range of soilsand climates make them one of the most popularflowering shrubs in Georgia. Although most peopleassociate azaleas with spring, several bloom insummer and fall. By carefully selecting plants, youcan have azaleas blooming at least eight months ofthe year.

Botanically, azaleas are members of the Ericaceae(Heath) family, which includes blueberries andmountain laurel. All azaleas are rhododendrons,and both are in the genus Rhododendron. The term“rhododendron,” however, is commonly used torefer to the group of plants usually with large,leathery, evergreen foliage, while “azalea” refers tothose with smaller, thinner leaves. Generally,azaleas and rhododendrons have the same culturalrequirements.

The Royal Horticultural Society in Londonmaintains an International Rhododendron Registrythat lists over 800 species and several hundrednamed cultivars. To be registered, a cultivar musthave a unique name and unique characteristics thatset it apart from others. Some hybridizers in theUnited States register their new cultivars with theRhododendron Society of America.

Grouping Azaleasby Characteristics

Azaleas are grouped into categories based on anumber of plant characteristics, including whetherthey are evergreen or deciduous (shed their foliagein winter), and whether they are a native plant

species or an introduced cultivar. Evergreen azaleasare described according to flower form, petal shape,variation in petal colors, plant size, time of bloomand growth habit. Many hybrid evergreen cultivarsare grouped according to the name of the plantbreeder who introduced them or the location wherethey were developed. These various groups andcharacteristics are described below.

Evergreen vs. DeciduousEvergreen azaleas maintain some of their leaves

throughout the year, while deciduous azaleas losetheir leaves in autumn.

Most evergreen azaleas originated in Japan, butsome came from China, Korea or Taiwan. Severaldeciduous azaleas are native to North America;others originated in Eastern Europe, Japan, Chinaand Korea. Others come from hybrid crosses.

Flower Forms and Petal ShapesAzaleas are often described according to the

shape or form of their flower. In order to under-stand the terminology used to describe flowerforms, it is helpful to review the parts of a flower(Figure 1). The stigma, style and ovary make up thefemale part of the flower. These three parts arecollectively called the pistil. The male part of theflower includes the anthers and filament, whichmake up the stamen. The petals are the showy partof the flower. Below the petals are the sepals. Insome flowers, the sepals are green and leaf-like,while in others they are colored like petals.

Deciduous azaleas typically have tubular flowerswith long stamens that extend beyond their petals.Evergreen azaleas, on the other hand, may have awide variety of flower forms. Figure 2 shows sixflower forms used to describe the flowers of ever-green azaleas.

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Single flowers consist of five or more petals withfive to ten stamens and a single pistil. This is themost common flower form. Semi-double flowershave had some stamens transformed into petals.Double flowers have had all their stamens trans-formed into petals. Hose-in-hose types consist oftwo flower forms that appear to be inserted intoone another; the top flower is derived from thepetals and a lower flower consists of colored sepals. Then there are semi-double hose-in-hose types,which combine the features of semi-double andhose-in-hose forms, and double hose-in-hose types,which combine the features of double and hose-in-hose forms. Hose-in-hose and double flower formstend to hold their blossoms after flowering. Theblossoms turn brown and wither on the plantinstead of dropping off.

Azaleas also may have a wide variety of petalshapes, including strap-like petals, star-shapedpetals, spider-like petals or round petals. Petals maybe one solid color, or they may be flecked orbordered in a different color.

Time of BloomAnother way azaleas are grouped is whether they

bloom early, mid-season or late. Early floweringtypes generally bloom from mid-February throughMarch, mid-season types bloom in late April andMay, and late-flowering types bloom from Junethrough October.

Native vs. Introduced Cultivars and HybridsNative AzaleasSeveral species of azaleas are native to Georgia

and the Southeast. Their flower color ranges fromwhite to pink, yellow, orange, scarlet or crimson,with several shades in between. Plant size is alsovariable, ranging from 3 feet to more than 20 feet.Although native azaleas are considered more adap-table and more hardy than introduced species, it isimportant to approximate their native growingenvironment if they are to be grown successfully.

The following are some native azalea speciesfound in Georgia:

Alabama Azalea, R. alabamense [ah-luh-ba-MEN-see] bears white flowers with a yellow blotch.It has a lemony-spice fragrance. This low to mediumsize shrub grows in Alabama and western Georgia.

Figure 1. Parts of a flower.

Figure 2. Flower forms.

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Piedmont Azalea, R. canescens [kuh-NES-enz] has white to pinkish tubular flowers with stamenstwo to three times longer than the petals. This tall-growing plant may attain a height of 15 feet. Somehave flowers with a musky-sweet, honeysuckle-likefragrance. As the common name implies, the Pied-mont Azalea is native to the Piedmont region ofGeorgia and other states.

Flame Azalea, R. calendulaceum [kuh-len-dew-LAY-see-um] has flower colors ranging from brilli-ant shades of yellow to orange or red, with a largeprominent yellow to orange blotch on the upperlobe (petal). Its flowers tend to be larger than theother native species. Flame azalea is native from theAppalachian Mountains to the Piedmont region.

Sweet or Smooth Azalea, R. arborescens [ar-bo-RES-enz] has white flowers, sometimes with a pink-ish tinge, and red stamens. It has glossy leaves andred fall foliage. Flowers have a strong, cinnamon-like fragrance. This species is native to west-centralGeorgia. It may attain a height of 8 feet.

Coastal or Dwarf Azalea, R. atlanticum [at-LAN-tih-kum] has white flowers that sometimes areflushed with pink. The plant grows 3 to 5 feet talland is smaller than most of the other native species. It is native to the Coastal Plain from Pennsylvaniato Georgia. Flowers have a rose-like fragrance.

Pinxterbloom Azalea, R. periclymenoides [pair-ih-kly-men-NOY-deez], previously classified as R.

nudiforum, has narrow, wavy flowers that are eitherwhite, pale pink or deep pink. It is native from theAppalachian Mountains to the Piedmont andCoastal Plain.

Swamp Azalea, R. viscosum [viss-KO-sum] has white to pink flowers that have a spicy, clover-likefragrance. The plant is variable in size and usuallygrows in low areas along stream banks from Maineto Georgia and west to Texas.

Florida Azalea, R. austrinum [aw-STRY-num]has yellow to orange flowers with a reddish tube.Some plants have a lemony fragrance. This tall-growing species can be found in Florida and theGeorgia-Alabama Coastal Plain.

Cumberland Azalea, R. cumberlandense [kum-bur-lan-DEN-see], previously classified as R. bakeri, has bright orange-red flowers. Plant height variesfrom 1 foot up to 6 feet. It can be found from theKentucky-Tennessee-Cumberland plateau to themountains of north Georgia.

Oconee Azalea, R. flammeum [FLAM-ee-um],previously classified as R. speciosum, has yellow, yellow-orange or red flowers with a large yellowblotch on the top lobe (petal). This species is nativeto low elevations in open woods and on slopesacross central Georgia.

Plumleaf Azalea, R. prunifolium [prew-nih-FO-lee-um] has flowers that range in color from apricotto orange or red. The petals have a deep red blotch.

Strap-likePhoto: Richard Clapp

Red selfPhoto: Frank Bryan

SectoredPhoto: Frank Bryan

Figure 3. Petal Shapes and color variations.

Star-shapedPhoto: Richard Clapp

Round petalPhoto: Frank Bryan

Spider-likePhoto: Frank Bryan

Flecked/stripedPhoto: CES slides

Margins/bordersPhoto: Allison Fuqua

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Piedmont azalea, R. canescensPhoto: Frank Bryan

Alabama azalea, R. alabamensePhoto: Frank Bryan

Flame azalea, R. calendulaceumPhoto: Frank Bryan

Sweet or Smooth azalea, R. arborescensPhoto: Frank Bryan

Coastal or Dwarf azaleaR. atlanticum Photo: Richard Clapp

Pinxterbloom azaleaR. periclymenoidesPhoto: Frank Bryan

Oconee azalea, R. flammeumPhoto: Richard Clapp

Plumleaf azalea, R. prunifoliumPhoto: Frank Bryan

Swamp azaleaR. viscosumPhoto: Richard Clapp

Florida azalea, R. austrinumPhoto: Frank Bryan

Cumberland azaleaR. cumberlandensePhoto: Richard Clapp

Plants are usually 5 to 8 feet tall, although somemature plants may attain a height of 20 feet.Plumleaf Azalea is native to a small region in

southwest Georgia and eastern Alabama. It is thesignature plant of Callaway Gardens in PineMountain, Georgia.

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Deciduous HybridsNative azaleas have been crossed to produce

many colorful, deciduous hybrid cultivars. Theseinclude ‘Exbury,’ ‘Knap Hill,’ ‘Ghent’ and relatedhybrid groups developed in England and Belgium.Because of their native-azalea parentage, severalhybrids are fragrant. Most of these, however, do notgrow well in Georgia, where the climate is hot anddrought is common.

Selected forms and crosses of native azaleas havebeen made at Transplant Nursery in Lavonia,Georgia, and by the late Fred Galle at CallawayGardens in Pine Mountain, Georgia. Crosses of theEnglish cultivars with the native Florida azalea havebeen made by Dr. Eugene Aromi and at Dodd andDodd Nursery in Mobile, Alabama. These hybridshave outstanding colorful blooms, and they canwithstand hot weather. Among the adapted selec-tions is ‘Gibraltar,’ a Knap Hill deciduous hybridthat performs better in central Georgia than mostEnglish and Belgian deciduous cultivars. It hasfragrant, frilled, crimson-orange flowers in a ball-shaped cluster. ‘Red Pepper’ (vivid red flowers) is anexample of a heat-tolerant Aromi cross. ‘StonewallJackson’ and ‘Admiral Semmes’ are examples ofheat-tolerant Tom Dodd crosses.

Introduced (Non-native) andHybrid Evergreen AzaleasDr. Fred Galle, former Director of Horticulture at

Callaway Gardens in Pine Mountain, Ga., describedmore than 70 hybrid groups of evergreen azaleas inhis book on azaleas (See “Suggested References”),and many more have evolved since then. Some ofthe major hybrid groups are described below.

Kurume Hybrids: Kurume azaleas are one of themost commonly grown azaleas in Georgia. Theywere imported from Kurume, Japan, to the ArnoldArboretum in Boston in the early 1900s and soonmade their way into the nursery trade. MostKurume hybrids are low- to medium-growing

shrubs (2 to 3 feet), but a few grow to 5 to 6 feet.Flowers are small but quite numerous, oftenmasking the foliage. Colors range from white topink, salmon or red, and some are bicolored. Mostare cold hardy throughout Georgia. PopularKurume hybrids include ‘Hinode Giri’ (rose-redflowers), ‘Coral Bells’ (soft pink flowers), and‘Snow’ (white flowers).

Southern Indian Hybrids: Southern Indian(also called Southern Indica) hybrids were dev-eloped from plants at Magnolia Plantation inCharleston, S.C., and therefore are well adapted tothe southern and coastal regions of Georgia. Theyare not reliably cold hardy in the northern half ofGeorgia, however. Most Southern Indian azaleas arefast growing and become quite large (5 to 8 feet talland 5 to 10 feet wide), making them undesirablefor foundation plantings. In south Georgia, they areoften planted under pine trees, where they havefiltered shade and plenty of room to grow.

Most Southern Indian hybrids bloom after theKurume hybrids. Popular cultivars include ‘For-mosa’(deep magenta-purple flowers), ‘GeorgeLindley Tabor’ (white flowers with purplish-pinkblotch and purple throat), and ‘Delaware ValleyWhite’ (pure white flowers with ruffled petals).

Glenn Dale Hybrids: Glenn Dale hybrids weredeveloped by B.Y. Morrison at the U.S. Departmentof Agriculture Plant Introduction Station in GlenDale, Maryland. More than 450 cultivars werehybridized from variable parentage. They are coldhardy to -10 degrees F and have a wide range ofbloom times, flower colors, flower forms and plantgrowth habits. Many are not widely available in thetrade, but their unusual flower colors and combina-tions of colors make them appealing. Interestingcultivars include ‘Zulu’ (vivid purple flowers withdark blotch), ‘Cinderella’ (white and red flowers orwhite stripped with red), ‘Ambrosia’ (deep yellow-pink flowers), and ‘Sagittarius’ (vivid pink flowerswith orange undertones).

‘Admiral Semmes,’ a Tom Doddhybrid. Photo: Frank Bryan

‘Gibralter,’ a Knap Hill hybridPhoto: Frank Bryan

‘Stonewall Jackson,’ a Tom Doddhybrid. Photo: Frank Bryan

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Back Acre Hybrids: Back Acre hybrid hybridswere also developed by B. Y. Morrison after hisretirement to Pass Christian, Mississippi, in 1964,where he continued his azalea breeding work on hisfarm called Back Acres. More than 50 Back Acrecultivars resulted from his crosses. Plants have awide array of flower colors and unusual color com-binations, and many have frilled or double flowers.Examples are ‘Marian Lee’ (white petals with a tintof pink and carmen-red border), ‘May Blaine’ (lightpurple double flowers), and ‘Debonair’(vivid pinkflowers with deep pink edges and light pink togreenish centers).

Robin Hill Hybrids: Robin Hill hybrids weredeveloped in New Jersey, so they are cold hardythroughout Georgia. This group, consisting of 69cultivars, is noted for having attractive foliage andlarge flowers that offer a spectrum of colors andcolor blends, many with soft pastel hues. Robin Hillazaleas bloom late and thrive in either sunny orsemi-shady locations. Most plants are low growing(2 to 3 feet). Cultivars include ‘Nancy of Robin Hill’(pastel-pink semi-double hose-in-hose flowers),‘Olga Niblett’ (white flowers with yellow-greenthroat), and ‘Conversation Piece’ (white to purple-pink flowers having wavy edges).

August Kehr Hybrids: Dr. August Kehr, formergeneticist with the U.S. Department of Agriculture,developed some spectacular azalea cultivars havingdouble or semi-double camellia-like flowers.Cultivars include ‘Anna Kehr’ (double rosey-pinkflowers with wavy edges), ‘Mary Lou Kehr’ (lightpink, semi-double fragrant flowers), ‘Great Expec-tations’ (reddish-orange double flowers), and‘White Rosebud’ (white double flowers with yellow-green center). The plants are hardy to 0 degrees F.

Gable hybrids: Gable hybrids were introducedby the late Joseph B. Gable, a nurseryman andhybridizer in Stewartstown, Pennsylvania. They areamong the hardiest evergreen azaleas, adaptable tohardiness zone 6b (to -5 degrees F). They bloom

mid-season and have a dense, spreading growthhabit and medium height (5 to 6 feet). Severalcultivars have double, hose-in-hose flowers thatlook like roses. The cultivar ‘Rosebud,’ for instance,has purplish-pink double rose-like flowers. Othercultivars include ‘Big Joe’ (purplish-pink flowershaving a brown blotch), ‘Elizabeth Gable’ (deep redflowers with frilled edges), and ‘Polaris’ (whitehose-in-hose flowers with greenish throat).

Linwood Hybrids: Linwood hybrids were devel-oped for greenhouse forcing and the florist trade.Flowers are double and semi-double, and most arehose-in-hose types, 1½ to 2½ inches across. Plantsare generally low-growing. Many are hardy to 0degrees F. Examples are ‘Linwood Lavender’ (vividpurple flowers, semi-double and hose-in-hoseform), ‘Janet Rhea’ (strong fuchsia-colored flowerswith white edges, semi-double, hose-in-hose form),and ‘Hardy Gardenia’ (double white flowers withhose-in-hose form).

Pennington Hybrids: The Pennington hybridgroup, consisting of 16 named cultivars, was devel-oped by the late Ralph Pennington in Covington,Georgia. His former nursery had one of the largestcollections of azaleas in the Southeast. MostPennington hybrids grow 3 to 6 feet tall and arehardy to at least 5 degrees F. Examples are ‘RalphPennington’ (single white flowers with a greenishblotch), ‘Beth Bullard’ (yellowish pink flowers, 3 to4 inches across) and ‘Bill Bullard’ (reddish-orangeflowers).

Harris Hybrids: The Harris hybrid group wasdeveloped by James Harris in Lawrenceville,Georgia. Several cultivars have large vivid-redflowers with light-colored centers and dark margins.Some have a cascading growth habit and areexcellent for hanging basket culture. Most bloommid-season. ‘Pink Cascade’ (deep yellow-pinkflowers with red blotch) is one of the popularcultivars. Others include ‘Fascination’ (singlepinkish-white flowers with deep-red borders),‘Parfait’ (pastel pink flowers with red dots), and

‘Marian Lee,’ Back Acrehybrid. Photo: Richard Clapp

‘George Lindley Tabor,’Southern Indian hybrid Photo: Frank Bryan

‘Coral Bells,’ Kurume hybridPhoto: Allison Fuqua

‘Cinderella,’ Glenn Dale hybridPhoto: Frank Bryan

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‘Midnight Flare’ (single, deep red flowers with wavyedges).

Satsuki Hybrids: Satsuki hybrids from Japanconsist of hundreds of cultivars. In Japanese, Satsukimeans fifth month of the Japanese lunar calendar(June). So plants bloom late (May, June and July),when most other azaleas are no longer blooming.Single, hose-in-hose and double flower forms areavailable. Flower size ranges from less than 1 inchto more than 5 inches across. Flower patterns in-clude solids, stripes, multicolored sections, coloredrings or margins, speckles and combinations ofthese. Many cultivars have variations of flower colorand patterns on the same plant. Popular cultivarsinclude ‘Pink Gumpo’ (single, light-pink ruffledflowers), ‘White Gumpo’ (single, white flowers withsmall flecks of purplish pink and a light-greenblotch), and ‘Wakaebisu’ (deep yellow-pink flowerswith rounded petals, hose-in-hose form).

Pericat Hybrids: The Pericat hybrids weredeveloped in Pennsylvania for greenhouse forcing.Unfortunately, many cultivars in this group are notreadily available in the nursery trade. ‘HamptonBeauty,’ however, is obtainable. It has deep-pinkflowers with a dark pink blotch. Pericat hybrids aregenerally of medium height (3 to 5 feet), bloommid-season, and are as cold hardy as Kurumehybrids (zone 7a — to 0 degrees F).

Encore Hybrids: Encore hybrids were developedby Robert Lee in Independence, Louisiana, and areamong the most popular azaleas on the markettoday because they bloom both spring and fall. Thenames of the cultivars in this group begin with theword autumn, due to their fall-blooming charac-teristic. Most grow to 3 to 5 feet high and wide.Examples are ‘Autumn Rouge’ (rose-colored, semi-double flowers), ‘Autumn Embers’ (bright-red,semi-double flowers with wavy edges), and‘Autumn Amethyst’ (single, vibrant purple flowers).

‘Janet Rhea,’ Linwood hybridPhoto: Richard Clapp

‘Fascination,’ Harris hybridPhoto: Frank Bryan

‘Wakaebisu,’ Satsuki hybridPhoto: Richard Clapp

‘Hampton Beauty,’ Pericat hybrid.Photo: Allison Fuqua

‘Beth Bullard,’ Penningtonhybrid. Photo: Richard Clapp

‘Anna Kehr,’ August Kehrhybrid. Photo: Richard Clapp

‘Rosebud,’ Gable hybridPhoto: Allison Fuqua

‘Nancy of Robin Hill,’ RobinHill hybrid. Photo: Richard Clapp

‘Autumn Rouge,’ Encore hybrid.Photo: Flowerwood Nursery

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Considerations When Selecting Plants

Cold HardinessWhen selecting azaleas, check the cold hardiness

zones to which they are adapted. Cold hardinesszones are based on the average winter temperatureof a region of the United States. In Georgia, thereare five cold hardiness zones, ranging from zone 6bin the north Georgia mountains to zone 8b insouthern and coastal Georgia (see Figure 4).Southern Indian hybrids, for instance, are bestadapted to zones 8a and 8b and may not be reliablycold hardy in zone 7.

Flowering SequenceNative azaleas, as well as the introduced hybrids,

bloom at different times of year, so planting anassortment of species and hybrid cultivars extendsthe floral display in the landscape. Table 1 (page11) shows the flowering sequence of several nativeazaleas.

Likewise, when selecting evergreen azaleas, youcan achieve up to 8 months of color with azaleas bycarefully selecting and matching plants from thevarious hybrid groups (Table 2, page 11). For in-stance, for early spring color, plant Kurume orPericat hybrids. In south Georgia, Southern Indian

hybrids provide early spring color. Add to these afew Back Acre hybrids for color in May and Satsukihybrids, such as Pink Gumpo or White Gumpo, forlate May/early June flowers. Then add a few Encorehybrids that re-bloom in August through fall frost,and the color show lasts from early spring to latefall.

Mature Plant Size and Flower ColorBe sure you know the mature size of plants so

they can be grouped according to height in thelandscape. Place tall plants in the background andshort plants in the foreground. Also, make certainthe flower colors are harmonious in case theirbloom periods overlap. Orange-flowering cultivarsoften clash with pinks and reds, so plant thesecolors in separate locations. Also, planting three ormore plants of the same cultivar in a group providesa more appealing color display than a hodge-podgeof different cultivars.

The best time to shop for azaleas is when theyare in bloom so you can see their flower colors andforms. Also, by purchasing plants in bloom, youwill know they are true to type and not mislabeled.

Plant HealthBuy plants that are sturdy, well-branched and

free of insect damage or diseases. Avoid plants withweak, spindling growth and a poor root system.Before purchasing plants, examine their roots bycarefully placing your hand over the top of the rootball; invert the plant and slowly remove the con-tainer. The roots should appear healthy and lightbrown, not dark brown or rotted.

Your Landscape NeedsLike other plants in the landscape, buy azaleas

with a specific objective in mind. Consider howthey will fit your landscaping plan. Perhaps youwant to create a dazzling display at the entrance ofyour home or a colorful reflection in a water fea-ture. You may want a particular color that blendswell with other plants in a perennial or shrubborder, or you may want just one plant to provide adramatic focal point. Whatever your intentions, useazaleas to complement other plants in the land-scape, not overshadow them.

Figure 4. Cold Hardiness Zones in Georgia.

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Table 1. Flowering sequence of several native azaleas

Mar Apr May June July Aug Sept Oct Nov

R. canescens ***********R. austrimun **********R. flammeum ************R. viscosum *************************R. prunifolium ****************************R. aborescens ************

Table 2. Flowering sequence of several hybrid evergreen azalea groups

Mar Apr May June July Aug Sept Oct Nov

Kurume *********Glenn Dale ********************Gable *********Southern Indian *****Back Acre ********Robin Hill ****Satsuki **************Encore ***** *************************

Planting TimeAzaleas can be planted successfully any time of

year, provided they can be watered during estab-lishment. Fall planting is best because it is lessstressful to the plant than spring and summer plant-ing. During the fall, temperatures are cooler andplants are going dormant. As top growth decreases,there is less demand on the roots for water andnutrients. Roots continue to grow and becomeestablished throughout the fall and winter months,even when the top is dormant. By spring, the well-established roots are ready to support new growthand flowers.

Site SelectionAzaleas thrive in moist, well-drained soils high

in organic matter. Filtered shade is best since somelight is necessary for flower bud formation. Anexposure with morning sun and afternoon shade isideal. Avoid planting azaleas near unshaded side-walks, driveways or west-facing walls because thesesurfaces radiate heat that may cause moisture stressduring the hot summer months.

Azaleas will not survive in wet, poorly-drainedsoil. Do not plant in depressions where water maypuddle after rain or near downspouts where theyexperience wet/dry fluctuations in soil moisture. Onthe other hand, azaleas are sensitive to drought andrequire irrigation during periods of limited rainfall.

Azaleas prefer acidic soils having a pH between4.5 to 6.0. A soil test, available for a nominal feethrough your local county Extension office, willdetermine the pH and nutrient content of your soiland provide recommendations for fertilizer. Whengrown in soils having a pH above 6.0, plants mayappear anemic when certain nutrients such as ironbecome deficient. Materials commonly used tolower soil pH are wettable sulphur or ferrous sul-fate. Do not use aluminum sulfate to acidify thesoil; it has been shown to be toxic to azalea roots.

Avoid planting azaleas under trees. Althoughtrees provide filtered shade, they compete withazaleas for moisture and nutrients.

Planting ProceduresBefore planting azaleas, always water them tho-

roughly. A dry root ball is difficult to re-wet once itis in the ground.

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When planting container-grown plants, carefullyremove them from the pot and examine their roots.If the plants appear pot-bound and have a thick,dense mat of fibrous roots along the surface of theroot ball, used a knife to make three to six verticalcuts, about 2 inches deep, equally spaced aroundthe sides of the root ball. Then use your hands togently loosen the roots where cuts were made andpull the roots outward. This process stimulates newroot growth and allows water and nutrients topenetrate into the root mass. If the roots are notpot-bound, it is not necessary to slice them with aknife, but it is beneficial to loosen and pull themoutward with your hands.

When planting an individual plant, dig theplanting hole two to three times wider than the rootball of the plant but no deeper than the root ball.Likewise, when planting a group of azaleas, culti-vate the planting area no deeper than the depth ofthe root ball. This prevents the root ball fromsettling after planting and becoming stressed.

Thoroughly mix organic matter, such as groundpine bark, shredded decayed leaves or compost,into the soil until the mixture is one-third to one-half organic matter. Then, backfill with theamended soil, and use your hands to firmly pack itin the bottom of the hole to minimize settling.

Planting depth is critical because azaleas areshallow-rooted plants. In sandy soils, set the rootball in the hole so the top is about 1 inch above thesurrounding soil grade. In clay soils and poorlydrained soils, place the top of the root ball 2 to 4inches above the soil grade, gradually sloping thesoil to meet the original grade. This allows forsettling and assures that the roots will be in the

upper layer of soil where they can readily obtainoxygen, water and nutrients (Figure 4).

Once the plant is in place and at the properdepth, backfill with amended soil, and use yourhands to firmly pack the soil around the roots.

Don’t fertilize at planting time. Fertilizer candehydrate and injure sensitive new roots. Wait untilthe plants are established before fertilizing them.

Apply 3 to 4 inches of an organic mulch such aspine straw, pine bark mini-nuggets or shreddedleaves on the surface. Use your hands to pull themulch away from the trunk an inch or two. Thishelps keep the trunk area dry and reduces thechances of wood decay. It also discourages rodentsfrom gnawing on the trunk. Organic mulchesgradually decompose and provide nutrients to theplants.

The final step in planting, and one of the mostimportant, is to water thoroughly immediately afterplanting. Apply water slowly so the soil can absorbit without causing run-off.

MaintenanceMulching

Mulching is a simple yet beneficial culturalpractice for azaleas. Mulches conserve water in thesoil, insulate roots against summer heat and wintercold, and discourage weeds. Replenish mulchesannually, as needed, to maintain a 3- to 5-inch layeron the soil surface. Fine-textured organic mulchessuch as pine straw or shredded bark are best. Fallleaves are an excellent mulch.

Figure 4. Planting depth.

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WateringBecause azaleas are shallow-rooted, they are

among the first plants in the landscape to showmoisture stress. Leaves may turn gray-green or theymay wilt, curl inward or scorch along their mar-gins. Pull back a small area of mulch near the plantcanopy once a week in summer and check the soilmoisture level. When the soil appears dry, waterthoroughly to wet the soil to a depth of 8 to 12inches. One inch of water (6 gallons applied over10 square feet) is enough to saturate most soils to a12-inch depth. Use drip irrigation or a soaker hoseto apply water slowly at a rate the soil can absorb,and avoid flooding the soil all at once. Overheadirrigation can be used, but it encourages foliardiseases like petal blight and azalea leaf gall (see“Diseases”). If overhead irrigation is used, irrigate inearly morning so the moisture will be evaporatedfrom the foliage by the rising sun.

FertilizationUnlike other shrubs in the landscape, azaleas are

shallow rooted and can be easily injured by excessfertilizer. In fact, some experienced azalea growersdo not apply chemical fertilizes at all. They havefound that plants usually can obtain sufficientnutrients for growth and flowering from the organicmatter added to the planting hole and from thedecaying mulch on the soil surface.

Supplemental fertilizers, however, are occa-sionally needed. Pale green leaves or inter-veinalchlorosis are good indicators of a need for fertilizer.A soil test, available for a nominal fee through yourlocal county Extension office, is the most scientificway of determining what type of fertilizer is best. If

soil test recommendations are not available, anazalea/camellia specialty fertilizer is generallyrecommended. This fertilizer contains primary,secondary and minor nutrients specifically formu-lated for azaleas. Because fertilizer analysis andnutrient content varies from product to product,follow manufacturer recommendations on appli-cation rate.

Apply fertilizer just after flowering. On spring-flowering cultivars, a second application of fertilizercan be made in June, at one-half the spring rate, ifnecessary. Avoid fertilizing after July 1 because budset and winter hardiness may be reduced.

Broadcast fertilizer over an area extending 4 to 6inches from the trunk to beyond the dripline oredge of the canopy. Be careful when broadcastingfertilizer over the top of plants, because the fertilizergranules may collect in the leaf whorls and causefoliar damage as it dissolves. Always fertilize whenthe foliage is dry, then use a broom or rake to brushresidual fertilizer from leaves or stems. Applyoverhead irrigation soon after application to washany residual fertilizer from the foliage and todissolve the fertilizer applied. Do not remove themulch when fertilizing. The fertilizer will dissolveand move through the mulch with irrigation waterand rain.

The old adage “if a little is good, a lot is better”certainly does not hold true when fertilizing azaleas.Over-fertilization may cause foliar burn, suddenleaf-drop or death of the plant.

PruningThe best time to prune azaleas is after they

bloom. Always prune, however, with a purpose inmind, not just because it is the time to prune. Someplants may need pruning to remove tall, lanky

Pine straw mulch. Photo: Frank Bryan

Drip irrigation. Photo: Gary Wade

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growth or vigorous suckers that detract from theoverall form and shape of the plant. It may bedesirable to prune to maintain a more compactform. Sometimes it is necessary to prune old, over-grown plants to rejuvenate them or to reduce theirsize. Like many other broadleaf plants, healthyazaleas can be pruned to within 6 to 12 inches ofground level and will respond with an abundanceof new shoots growing from the old wood.

Spring-flowering azaleas form their blossombuds for the next year during the summer, so avoidpruning them after July 1.

Two pruning techniques are used: heading andthinning. Heading is the indiscriminate cutting backof branches to a uniform length (Figure 5). Shearingis a type of heading. It is done to reduce the size ofthe plant and to increase the number of branches.Rejuvenating old, overgrown plants by cutting themback close to ground level is another form of head-ing. New shoots emerge within 6 inches of whereeach pruning cut is made, so heading encourages anabundance of new shoots.

Thinning is the complete removal of a branchback to another branch, bud or main trunk (Figure5). It is used to remove leggy branches that extendbeyond the canopy of the plant, to reduce the sizeof the plant, or to remove any damaged or diseasedwood. Thinning is the preferred pruning techniquebecause it opens up the canopy, improves air flowand helps minimize diseases. It also results in amore natural growth form than heading andrequires less routine maintenance.

Azaleas are favorite plants of bonsai growers.Bonsai is an ancient Japanese art form in which

plants are trained as miniature trees in containers.Special skills and patience are required to developazaleas into bonsai specimens.

Occasionally, azaleas are pruned and trained togrow as single-trunk tree forms, or standards. Insome Japanese gardens, groups of azaleas arepruned into tight geometric shapes and appear likeflowing clouds when in bloom.

Common Azalea ProblemsCultural and Environmental Problems

Leaf ChlorosisLeaf Chlorosis, characterized by dark-green leaf

veins with yellow areas between them, usuallyindicates a deficiency of iron. Iron deficiency maybe caused by high soil pH or high phosphoruslevels in the soil. Leaf chlorosis also may be causedby poor drainage, nematode injury to the roots, orexcess fertilization. Determining the real cause ofthe chlorosis is the first step in correcting thecondition.

If the problem is iron chlorosis, it can be cor-rected by applying ferrous sulfate to the soil at a rateof 1 ounce (2 tablespoons) per 10 square feet. For aquick but only temporary improvement in theappearance of the foliage, ferrous sulfate can bedissolved in water (1 ounce in 2 gallons of water)and sprinkled on the foliage. Some garden centerssell chelated iron, which provides the same results.Follow the label recommendations for mixing andapplying chelated iron.

Small, yellow leaves and stunted growth aresigns of water stress brought on by water-logged soilor wet/dry fluctuations in soil moisture. Foliarwilting and bronzing are other symptoms some-

Prune azaleas after flowering, if necessary. Photo: Gary Wade

Figure 5. Heading vs. thinning

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times shown by plants growing in wet, soggy soilconditions. In water-logged soils, roots die or arekilled by fungi and are unable to absorb water andnutrients. Avoid planting azaleas in low spots ornear drain spouts where water may stand after rainor irrigation.

Leaf ScorchLeaf scorch (death of leaf tissue along the mar-

gins) is usually caused by over-fertilization ordrought stress. It can also result from broadcastapplication of fertilizer when the foliage is wet.

Cold InjuryCold injury on azaleas may be expressed as foliar

browning, bud abortion, leaf drop or bark splitting.The type and severity of damage depend on a num-ber of factors, including the degree of hardiness ofthe plant at the time of the freeze, the location ofthe plant in the landscape, the severity and durationof the cold, and the daily temperatures prior to thefreeze. Selecting cold hardy cultivars, making certainthe plants are well-mulched and watered prior to afreeze, locating the plants in areas where they are

protected from cold northwest winds, and coveringthe plants with cardboard boxes or wrapping themin blankets, are ways to minimize freeze injury.Plants usually recover from leaf scorch or bud abor-tion, but they seldom recover from bark splittingwhen it occurs on the main trunk.

InsectsAzalea Lace BugAzalea Lace Bugs are major pests of azaleas. They

feed on the underside of leaves, but the damagethey cause is most apparent on the upper leafsurface, which appears stippled when groups ofadjoining leaf cells become chlorotic. Brown toblack droplets of excrement and old “skins” of thenymphs (immature lace bugs) are visible on theundersides of damaged leaves. Adult lace bugs areflattened and rectangular in shape and c to ¼ inchlong. The area behind the head and the wing coversform a broadened, lace-like covering over the bodyof the insect. The wings of most lace bugs are lightamber to transparent in color.

Bark splitting from freezePhoto: Frank Bryan

Left: Iron chlorosis. Photo: UGA Plant PathologyRight: Azaleas dying in poorly-drained soil. Photo: Gary Wade

Leaf scorch caused by over-fertilizationPhoto: Gary Wade

Bud freeze. Photo: Frank Bryan

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Lace bug nymphs are flat and oval with spinesprojecting from their bodies in all directions. A lacebug nymph goes through five growth stages (in-stars) before becoming an adult. At each stage thenymph sheds its skin (molts), and these old skinsoften remain attached to the lower surface ofinfested leaves.

Azalea lace bug eggs are football-shaped and aretransparent to cream colored. The eggs are found onthe lower leaf surface, usually alongside a leaf vein.Adult females secrete a varnish-like substance overthe eggs that hardens into a scab-like protectivecovering. The egg stage overwinters in leaves ofevergreen azaleas. There are four generations peryear. Control of the first generation in March mayreduce the need for additional insecticide applica-tions and conserve the many predators and an eggparasite that are natural control agents of the lacebug.

Azalea CaterpillarAdult moths of the azalea caterpillar are about 1

inch long and brown. Mature (2½ inches long)larvae have a reddish brown head, legs and “neck”area, while the body is black with rows of white orpale yellow spots. There is one generation per year.Larvae feed from late summer through early fall.Caterpillars feed together when they are young,then disperse as they get older. They overwinter aspupae in the soil. Entire branches can be defoliatedby large larvae.

Caterpillars can be removed by hand when onlya few are present. Bacillus thuringiensis may beapplied when caterpillars are numerous and are lessthan ¾ inch long. Residual insecticides can beapplied for larger larvae.

Azalea Bark ScaleThis insect prefers azalea or rhododendron but

can infest andromeda, maple, willow, poplar andother plants. There are two generations per year inGeorgia. Adult females may be c inch long. Whitefelt-like sacs are secreted in May that enclose thebody and eggs. Overwintering nymphs are about1/16 inch long, gray, and can usually be found intwig forks.

Azaleas can tolerate low numbers of theseinsects. Honeydew, sooty mold and leaf yellowingwith dieback are signs associated with infestation bythis insect. Beneficial insects often control thisinsect. Light pruning or dormant oil may be used tosuppress overwintering nymphs on twigs. Dormantoils and insecticidal soap may be used to controlcrawlers that emerge from eggs.

Southern Red MiteThis mite has a broad host range but is very com-

mon on broad-leaved evergreens including azalea.Red eggs overwinter on the underside of leaves.There are several generations each year, but they aremost active in the spring and fall. Adults are approx-imately 0.5 mm long. White stippling on upper andlower surfaces is characteristic. Leaves turn gray orbrown and may appear “dusty” from cast skins andegg shells.

When mites are suspected, tap leaves over whitepaper to dislodge mites. Count the slow-movingsouthern red mites, but also look for long-legged,faster moving predatory mites that may be feedingon these pests. Application of dormant oil in thewinter may reduce spring populations. Use of hor-

Azalea bark scalePhoto: www.bugwood.org,Clemson University

Southern red mitePhoto: Kris Braman

Azalea lace bug. Photo: Kris Braman

Azalea caterpillar. Photo: www.bugwood.org,Chris Evans

Azalea leafminer damagePhoto: Kris Braman

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ticultural oil or insecticidal soap may help conservebeneficial organisms. When heavy infestations ofmites are present, residual miticides may be needed.

Azalea LeafminerYoung larvae tunnel inside the leaf and form

elongate blotches in April or May. These blotchesmay resemble leaf spot diseases. Older larvae exitthe tunnels, curl the leaf tip and feed inside the curl.Large populations cause the leaves to turn brownand drop from the plant. There are two generations.Adult moths are about d inch long with wingsfolded. They are yellowish-brown with purplemarkings. Mature larvae are about ½ inch long.Treat in May if numerous. Shake plants in June andJuly to make adults fly and estimate whether re-treatment is necessary.

For information on controlling any of the insectslisted above, contact your local county Extensionagent or garden center professional, or visit thefollowing web sites:

http://www.caes.uga.edu/departments/ent/lpm/http://www.ent.uga.edu/pmh/Hm_Ornamentals.pdfhttp://www.ent.uga.edu/pmh/Com_Ornamentals.pdfhttp://www.caes.uga.edu/departments/ent/lpm/ornamentals/

ornamentals.html

DiseasesNumerous diseases affect azaleas in landscapes

and plant nurseries. The most common diseases aredescribed here. In order for a plant disease todevelop, three major factors need to be present atthe same time: 1) a susceptible host, 2) a disease-causing organism (pathogen) capable of causingdisease on that host, and 3) an environment thatfavors disease development — often humid, wetconditions. This is often referred to as the “diseasetriangle.”

To control plant diseases, at least one side of thedisease triangle must be removed. For example, if a

pathogen requires a wet leaf surface to infect, thenchanging irrigation type from overhead sprinklers todrip irrigation or soaker hoses, which do not wetthe plant foliage, can reduce disease development.For the following diseases, cultural methods and/orfungicides are used to control. Contact your localcounty Extension agent or consult the Georgia PestManagement Handbook for specific and currentfungicide control recommendations.

Leaf GallLeaf galls, caused by the fungus Exobasidium

vaccinii, are common on azalea in the spring duringwet, humid, cooler weather. The fungus invadesexpanding leaf and flower buds causing thesetissues to swell and become fleshy, bladder-likegalls. Initially, the galls are pale green to pinkish.Eventually, they become covered with a whitishmold-like growth. Fungal spores are producedwithin the white growth and are spread by water-splashing or wind to other expanding leaf or flowerbuds, or they adhere to newly formed buds, over-winter, and infect these buds the following spring.Older leaves and flowers are immune to infection.As the galls age, they turn brown and hard. Thedisease does not cause significant damage toaffected plants. It just looks unsightly.

Azalea leaf gall can be prevented in subsequentyears by removing the galls by hand as soon as theyare detected and destroying them before they turnwhite and release spores. Fungicides are generallynot needed or recommended for control of thisdisease.

Petal BlightPetal blight, caused by the fungus Ovulinia

azaleae, is a serious disease of flowering azaleas. Itstarts as pinhead-sized pale or whitish spots oncolored flowers and rust-colored spots on whiteflowers. The spots enlarge rapidly into irregular tanblotches. The flowers become soft, then slimy and

Azalea leaf gall. Photo: Jean Woodward

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fall apart when rubbed gently between fingers. Thistest distinguishes diseased flowers from thoseinjured by freeze damage, in which infected flowersdry and cling to the plant. The blight can spreadrapidly when plants are in bloom.

Small, black sclerotia (survival structures) areproduced on the infected flowers six to eight weeksafter infection. Blighted flowers fall to the ground orcan remain attached to the plant until flower budbreak the following year. Small cup-shaped struc-tures (apothecia) develop from the sclerotia in thespring. Fungal spores are propelled from thesestructures to flower buds in the lower plant canopy,or they are carried by wind to adjacent plants tocause new disease.

Rake and remove flower debris from beneathplants and, if possible, remove old flowers stillattached to plants. Apply new mulch around thebase of plants to serve as a barrier to new infection.On large azalea plantings, where it is not practicalto remove infected flowers, make weekly fungicideapplications beginning just before bloom andcontinue until the last buds open.

Rhizoctonia Web BlightDieback of the interior leaves of compact,

tightly-growing azaleas within irrigated landscapebeds may be due to a web or aerial blight caused bythe fungus Rhizoctonia. (Photo on page 19.) Rhizoc-tonia web blight is often seen during the warmer,humid summer months. Infection begins in theinterior of the plant as the fungus survives in thesoil or container rooting medium.

Infected leaves develop brown lesions andeventually the entire leaf will brown and separatefrom the stem. The affected leaves often remainmatted together by the fungus’s web-like growth(hyphae) that holds the brown leaves within thecanopy. As the temperature cools in the fall, thefungus stops growing and the matted leaves dropfrom the plant.

The disease in only a problem in landscape aza-leas that are sprinkler irrigated. Wet foliage and highhumidity favor infection. Use drip irrigation orsoaker hoses to irrigate landscape beds. Also, re-move fallen leaf debris from beneath plants. Fungi-cides can provide some control but should not berelied upon solely. Apply fungicides at the first signof disease and continue through the summermonths.

Twig BlightTwig blight of azaleas is caused by several fungi,

including Phomopsis and Botryosphaeria and infectslarger branches. Symptoms include wilting of leaveson only one or several branches but never on theentire plant. Eventually the entire branch turnsbrown and dies. If the bark is scraped off of infectedbranches, a reddish brown discoloration can befound underneath. Infection occurs throughwounds, fresh leaf scars and cracks in the bark.Environmental stresses such as drought and freezeinjury often predispose plants to infection.

Twig blight may be reduced by preventing mois-ture stress and stem splitting as much as possible.Prune out infected branches as soon as detected.Fungicide applications are ineffective in reducingtwig blight.

Phytophthora Root RotPhytophthora root rot can be one of the most

serious diseases of azaleas. It infects plants in poorlydrained soils or where plants are over irrigated andsoils remain saturated. The entire plant canopy maybecome off-color, dull or chlorotic (yellow). Stemsmay wilt, and eventually the plant dies. Roots ofaffected plants are darkly discolored and necrotic.

Azalea petal blightPhoto: Jean Woodward

Freeze injury instead of petalblight. Affected flowers do notbreak apart when rubbed gentlybetween fingers. Photo: Jean Woodward

Azalea petal blight sclerotiaPhoto: NC State University

21

The wood beneath the bark at the soil line may bediscolored reddish-brown.

Remove infected plants and correct excessive soilmoisture. The disease only develops in landscapebeds with too much water. Correct poor site condi-tions to reduce root rot disease development. Avoidover-watering, compacted soils and planting plantstoo deeply. Chemical control through fungicides isneither effective nor recommended in landscapes.

Poor Root Growth or Root Rot DiseaseAzaleas within landscapes often show symptoms

of thinning foliage or poor growth. This is mostlikely due to some kind of root injury or disease.Plants with poor roots cannot support a full leafcanopy, so interior leaves drop and all that remainsare tufts of new growth at the ends of branches.Root rot disease, planting plants too deep, plantingin compacted soils, girdling roots, over-wateringand/or over-fertilizing plants contribute to foliagedecline and poor plant growth. The only way todetermine the cause of the poor growth is to dig upthe plant and evaluate root health, pattern ofgrowth, and the soil and area in which the plantsare planted.

If roots are soft and brown, and slough offbetween your fingers when tugged, then the prob-lem is most likely a root rot disease, which is due toover-watering, or planting in an area with poor soildrainage or where water pools around plants. If theroot ball is flattened or roots are encircling the rootball, then the soil is compacted or the plant is root-bound with girdling roots. Compacted soils areprevalent in heavy clay soils, and they prevent rootgrowth downward and outward from the root ball.Always break apart root balls from container-grownplants upon transplanting. If roots are growing fromthe lower stems and branches, then the original rootball was planted too deep, which will kill the orig-inal root ball and force the plant to develop rootshigher within the plant canopy. Transplant plants atthe same level or slightly higher than they weregrowing in the container.

The only way to correct poor root and plantgrowth is to correct planting site conditions: avoidover-watering, break up compacted soils, redirectwater flow from gutter downspouts, etc., away fromlandscape beds, and do not plant plants too deeply.

Poor root growth.Photo: Jean Woodward

Rhizoctonia web blight.Photo: Jean Woodward

Internal discoloration caused by Phytophthora root rot.Photo: Virginia Tech

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Propagation of AzaleasAzaleas can be propagated from cuttings, seeds,

or by a process called layering. Most evergreenazalea cultivars are propagated from cuttings tomaintain their genetic purity.

To propagate azaleas from cuttings, take terminalcuttings (mid-June to September), 2 to 3 incheslong, when new growth has hardened. Make the cutjust below a node, and remove the lowest leaves.Then pinch out the terminal bud, leaving two tothree leaves on the stem.

Next, dip the cut end of the cutting in a rootinghormone, such as Rootone or Homodin, and insertit into a prepared growing mix. Many growingmixes are available in bags at garden centers andnurseries, or you can make your own by mixingfinely ground pine bark, perlite, vermiculite and/orsand. The medium should stay moist yet drain well.

Cuttings may be rooted in flats, cell packs, plasticdrink containers, milk cartons or other convenientand economical containers. Make certain the con-tainer has adequate drainage holes and drains well.Water the growing mix before and after the cuttingsare in place.

If you do not have a greenhouse, you can simu-late one by placing a clear plastic bag over therooting container and sealing it with a twist-tie.Place the container in a warm, shaded location, andcheck the moisture level frequently. If there is con-

densation within the bag, moisture level should beadequate. Some azalea growers place cuttings underartificial light because it enhances rooting.

Rooting time depends on cultivar, but most willbegin to form roots within 4 to 6 weeks. Once thecuttings are firmly rooted, they can be transferredinto larger containers. They should be ready fortransplanting into the landscape in about 1 yearand should be blooming in 2 to 3 years.

Azalea hybridizers and some hobbyists growazaleas from seed. Seeds are borne in terminal podsafter flowering. Harvest the pods in October,remove the seeds, and sprinkle them on top ofmoist milled sphagnum moss in a covered seedingflat. Place the flat under artificial lights (gro-lightsor full spectrum bulbs are recommended). Use atimer to control light duration so the seeds receive16 hours of continuous lighting each day. In 2 to 3weeks, small seedlings will appear. When they areabout an inch tall, transplant them into small, 3- to4-inch pots, and keep them moist. It takes about 3years to produce a blooming plant from seed.

A third way azaleas are propagated is by layering,a technique that induces root growth along an exist-ing branch. Two methods of layering are commonlydone: stem layering or air layering. Both methodsare slow and used only when a few plants aredesired.

Stem layering is done by selecting a vigorousbranch long enough to bend and touch the ground,at least 12 inches from the tip. Next, wound the

A plastic bag is used to createa mini-greenhouse.

Photos: Frank Bryan

Stem layering.Seed pods on native azalea.

Flat of rooted cuttingsready for transplanting.

Air layering.

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branch where it contacts the ground by removing a1-inch ring of outer bark all the way around thestem, or by making a slight cut in the branch at anangle about halfway through the branch. Cover thewounded area with 3 to 4 inches of soil, then placea brick or rock on top of the soil to hold the branchin place. Keep the area moist. After several weeks,roots will form in the wounded area, and the plantcan be separated from the mother plant and trans-planted.

Air layering is done in late spring on the previousyear’s wood. Select a vigorous branch and a locationalong the branch for the layer, then remove anyleaves in the immediate vicinity. Make a shallowcut, approximately 1 to 2 inches long, at an angleon the underside of the stem, being careful not tosever the stem. Then dust the cut with a rootinghormone and place approximately 1 cup of dampsphagnum moss around the cut stem and tie it inplace with string. Next, cover the moss with plasticsecured on both ends with twist-ties. Then cover theplastic with aluminum foil to reflect heat and toprevent heat build-up during the summer months.Rooting usually occurs within 6 to 12 months.

By purchasing healthy, pest-free plants adaptedto your area, planting properly, and following the

cultural guidelines provided in this publication, youwill be rewarded with years of colorful blooms andlasting landscape beauty.

Suggested ReferencesFoote, Leonard E., and Samuel Jones. 1989. Native

Shrubs and Woody Vines of the Southeast.Portland, Ore.: Timber Press.

Galle, Fred C. 1987. Azaleas. Portland, Ore.: TimberPress.

Reiley, H. E. 2004. Success with Rhododendrons andAzaleas. Portland, Ore.: Timber Press.

Towe, L. C. 2004. American Azaleas. Portland, Ore.:Timber Press.

Wade, Gary L., Frank Bryan, Albert Penland, andJim Thornton. Selecting and Growing Azaleas.PowerPoint Presentation CD-226, University ofGeorgia Cooperative Extension (available onloan from your local county Extension officeand for sale from the Oconee Chapter of theAzalea Society of America).

Callaway Gardens, Pine Mountain, Georgia.Photo: Frank Bryan

Bulletin 670 Reviewed September 2010

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