Over 1,700 trees representing more than 90 species comprise the Bucknell University Arboretum, a legacy representing over 150 years of wise stewardship and management. Trees representing 73 species and many of our most remarkable trees are marked with plaques corresponding to the map numbers shown on the back cover.

Tree Description Key N = Native to eastern North America I = Introduced NI = Native to North America, but not Pennsylvania

= Introduced species with potential to become invasive in Pennsylvania.⊗

Begin on the Academic Quad looking west When European settlers arrived in the Buffalo Valley in the eighteenth century, forests of oak, pine, American chestnut, and other native hardwoods covered the mountains visible to the west. The valley between was an open oak woodland, described in one early account as “wooded…with large but scattered trees, so that the grass grew abundantly and furnished good pasturage for the buffalo.”1 Such an open landscape was unusual for an otherwise densely wooded region. It was almost certainly maintained by aboriginal burning in order to provide habitat for wild game, including elk, deer, and the buffalo (bison) that gave the valley its name and to facilitate useful plant species, including fruit and nut trees.

In the wake of European settlement after the Revolutionary War, farm fields replaced the oak woodlands. Logging during the 19th and early 20th centuries denuded the mountain forests, but with the help of Depression-era conservation efforts, oak forests reclaimed the mountains. In recent decades, fire suppression has allowed red maple (a species formerly limited by low-intensity ground fires that oaks can withstand, but that kills maples) to thrive, creating a forest unlike any that existed in the past.

Introduced pests have also left their mark on our landscapes. The American chestnut was one of the most common and most valuable tree species throughout the Appalachians. Chestnut blight, a fungal disease, was first described in the US in 1904 and had eliminated chestnuts from the forests by 1945. Dutch elm disease similarly killed off most of the American Elms that once

1 Allen, J.A. 1877. History of the American Bison, Bison Americanus. Washington, D.C.: U.S. Geological Survey.

dominated Bucknell’s campus. Our hemlock, flowering dogwood, and ash trees all face a similar fate from introduced pests.

The most dramatic changes, however, have occurred where we have deliberately created environments by planting trees, shrubs, flower beds, and lawns for aesthetic and other reasons. Bucknell’s campus tree flora represents a combination of both formal constructions and echoes of the Buffalo Valley’s ecological history.

1. Japanese cherry, Prunus serrulata (rose family; I) Note the plaque on Marts Hall commemorating the gift of these trees. 2. Sugar maple, Acer saccharum (maple family; N) 3. Sweetbay magnolia, Magnolia virginiana (magnolia family; N)Magnolias and their nearest relatives represent an early branch within the phylum of flowering plants, distinct from the monocots and the eudicots. Magnolia flowers have primitive characteristics including radial symmetry, a large number of unfused floral parts, and similar morphology of the sepals and petals (referred to as tepals).

Exit Academic Quad between Bertrand Library and Vaughn Lit. 4. Douglas fir, Pseudotsuga menziesii (pine family; NI) Native to western North America, where it is an important timber species.5. Red maple, Acer rubrum (maple family; N)

Left to Tilton Garden 6. Panicled golden raintree, Koelreuteria paniculata (soapberry family; I) 7. Fringetree, Chionanthus virginicus (olive family; N)

Return to main tour route. 8. Common hackberry, Celtis occidentalis (elm family; N) 9. Princeton American elm, Ulmus americana 'Princeton' (elm family; N) American elms once dominated Bucknell’s landscape but fell victim to Dutch Elm Disease in the 1970s. Environmental Residential College students planted this naturally-occurring disease-resistant variety in 2008.10. Katsura, Cercidiphyllum japonicum (katsura family; I) A dioecious species (male and female flowers on separate trees), this specimen is a female; a male grows on the opposite side of the stairway.

Left between Olin and O'Leary Buildings 11. Franklin tree, Franklinia alatamaha (tea family; NI) Naturalists John and William Bartram discovered the only known grove of these trees along Georgia’s Altamaha River in 1765 and named the species for Benjamin Franklin. It was last seen growing wild in 1803 and survives today only in cultivation. All specimens alive today derive from seeds the Bartrams collected and cultivated in their Philadelphia botanical garden.12. Kousa dogwood, Cornus kousa (dogwood family; I)Kousa dogwood, from Asia, has been planted widely as a replacement for our native flowering dogwood because it has a similar appearance, but is highy resistant to dogwood anthracnose. The Kousa dogwood can be distinguished from the flowering dogwood by its later flowering time, the presence of large red berry-like fruits as well as by the shape of its leaves and buds.13. Blue spruce, Picea pungens (pine family; NI)Endemic to the central and southern Rocky Mountains.14. Weeping white pine, Pinus strobus ‘Pendula’ (pine family; N)

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Gardeners prize weeping varieties for the ornamental value of their unusual growth habit, which arises from a mutation that alters the balance of auxin and cytokinin hormones. Weeping trees display horizontal (plagiotropic) rather than vertical (orthotropic) growth of their branches and a reduction in apical dominance. 15. Japanese tree lilac, Syringa reticulata (olive family; I)16. Paperbark maple, Acer griseum (maple family; I)

Exit courtyard north; cross 7th St. to Roberts Quad17. American basswood, Tilia americana (linden family; N)

OaksThe genus Quercus includes ~400 species that are subdivided into five “sections,” three of which are represented in this quad: chestnut and white oak (white oak section-Europe, Asia & N. America), sawtooth oak (Turkey oak section-Europe and Asia), and scarlet oak (red oak group-the Americas). 18. Chestnut oak, Quercus prinus (beech family; N)19. Redbud, Cercis canadensis (pea family; N)20. White oak, Quercus alba (beech family; N)21. Sawtooth oak, Quercus acutissima (beech family; I)22. Scarlet oak, Quercus coccinea (beech family; N)

Exit between Roberts and Trax Halls; proceed east through the parking lot and down the sidewalk. Turn right and cross the lawn to #23.

23. Common persimmon, Diospyros virginiana (ebony family; N)The genus name means “food of the gods” in reference to the fruit, which are highly astringent until fully ripe, at which point they become very sweet.Proceed down the parking lot. Tree #24 is across Snake Road. 24. Norway spruce, Picea abies (pine family; I)

Continue down Snake Road (Caution!) to the grassy area where tree # 29 is visible. Cross Snake Road and follow the path south.

25. European larch, Larix decidua (pine family; I) [tree succumbed to a storm in 2012]Most members of the pine family are evergreen, but two genera are deciduous: larches and Metasequoia. The latter was known only from fossils until discovered growing in China during WWII, and is thus considered a “living fossil.” Larches are one of the dominant trees in European and Canadian boreal forests.26. Red oak, Quercus rubra (beech family; N)27. White oak, Quercus alba (beech family; N)This impressive white oak is the largest on Bucknell’s campus and, according to Forestry Association of Pennsylvania records, is one of the largest in Pennsylvania.28. Pin oak, Quercus palustris (beech family; N)Pin oak named for the many horizontally growing branches along the main trunk that form “pins” on the lower branches.

Cross Snake Road towards Health Services (Caution; no sidewalks)

Biogeography: The Acto-Tertiary GeofloraFrom 65-15 million years ago (mya), the northern continents were often connected and shared a warm climate that supported a continuous forest biome and flora. Climatic change during the past 15 million years fragmented the biome allowing distinct floras to evolve on each continent.

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Some taxa, such as pines, beeches and oaks, are present on all three continents. Others, such as tulip trees and hemlocks, did not survive Ice Age glaciations in Europe but persist in eastern Asia and eastern North America, which gives these two regions very similar forest floras.

Species transplanted to new continents often leave their enemies behind and thrive in their new habitats. This makes them attractive for cultivation but can lead to their becoming invasive. Introduced pest species may encounter new hosts lacking evolved defenses (e.g., chestnut blight). Such introduced organisms can have dramatic effects on biodiversity, soil nutrients, hydrology, fire regimes, and aesthetic values. Environmental damages, losses, and management exceed $100 billion per year in the U.S. alone.

29. White pine, Pinus strobus (pine family; N)Members of the pine family are, with one exception, native only to the northern hemisphere. Widely introduced to the southern continents in the last century, they have escaped cultivation and become invasive in many regions.30. Tulip poplar, Liriodendron tulipifera (magnolia family; N)This is one of our largest native trees, often growing to a height of 50 m (165’) or more. Liriodendron split from the rest of the magnolia family ~100 million years ago. The only other living species is the Chinese tulip tree. “Poplar” is a misleading common name, since Liriodendron is only distantly related to the true poplars in the genus Populus. 31. European beech, Fagus sylvatica (beech family; I)32. American beech, Fagus grandifolia (beech family; N)Fossil and biological evidence suggests that Fagus originated in Asia and spread to both Europe and North America. The North American beeches diverged starting ~15 mya, while the European beeches split from their Asian kin 5-2 mya.

North past small shed towards Public Safety Building33. Eastern hemlock, Tsuga canadensis (pine family; N)Pennsylvania’s state tree. Hemlock woolly adelgid, an insect pest introduced from Asia into North America in 1924 and to Pennsylvania in 1967, has spread through most of eastern hemlock’s native range causing widespread mortality. It was first recorded in Lewisburg in 1999. This insect feeds by sucking the phloem sap, thus desiccating young growing branches. The adelgid reproduces quickly, producing two generations per year. Their wooly egg sacs may be visible on the underside of the branches.34. Sycamore maple, Acer pseudoplatanus (maple family; I)

Cut across lawn towards the small evergreen (see arrow)35. Black walnut, Juglans nigra (walnut family; N)36. White ash, Fraxinus americana (olive family; N)Trees in the genus Fraxinus are under threat from an invasive insect, the emerald ash borer, first detected in Michigan in 2002. This insect has spread to the east and killed millions of trees in its wake. It arrived in Pennsylvania in 2007 and has since been observed in Union County. 37. Black cherry, Prunus serotina (rose family; N)38. Black locust, Robinia pseudoacacia (pea family; N.)The mature black locust is located ~10 yards down the slope. Invasive species have established in the wake of disturbance and are crowding out the native vegetation. For the past 5 years, student groups have worked to remove invasive species and have planted native redbuds and flowering dogwoods throughout this area. 39. American elm, Ulmus americana (elm family; N)

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This magnificent elm is clearly resistant to Dutch Elm Disease and provides a hint of what the campus might look like had the disease not been introduced.

Cross the parking lot, proceed between the Gateway buildings.40. Yellowwood, Cladrastis kentukea (pea family; N)

The GroveThe grove is a relic of the forest in which Bucknell’s campus was established. Tree-ring counts reveal that the oldest trees on the slope above you date to the 1770s. These trees most likely germinated in the wake of logging to provide timber for a sawmill operated by Lewisburg’s founder, Ludwig Derr, and located about 400 yards northeast of here. It is remarkable to think that every Bucknellian has passed under the oldest of these trees. 41. Pignut hickory, Carya glabra (walnut family; N)42. Cucumber magnolia, Magnolia acuminata (magnolia family; N)43. Osage orange, Maclura pomifera (fig family; N)During past interglacial periods this species grew throughout the U.S. and Canada, where it is now widely cultivated as an ornamental. Clearly able to tolerate a wide variety of environments, its natural range is limited to parts of Texas and Oklahoma. Why? Fleshy fruits are an adaptation to large animal dispersal, but no native species eats the softball-sized “oranges.” Most likely, the Osage orange retreated southwards during the last Ice Age, but its disperser went extinct, leaving it stranded. Species 23, 61, 63, and possibly 11 also appear to be ecological anachronisms.44. Black maple, Acer nigrum (maple family; N)Some taxonomists classify black maple as a subspecies of sugar maple. Black maple is more common in the Midwest and may have arrived on campus from a nursery there.45. Green ash, Fraxinus pennsylvanica (olive family; N) See #36 above.

Cross 7th Street to President's House. (Private residence; please do not enter the yard.)46. Ginkgo, Ginkgo biloba (ginkgo family; I)Ginkgo is not a flowering plant or conifer, but the sole surviving species of an ancient (at least 190 million years) division of gymnosperms (Ginkgophyta). It may have survived to the present only through cultivation at Buddhist temple sites in China, and debate continues as to whether G. biloba is extinct in the wild. This specimen is a female (Ginkgo is dioecious) as evidenced by the large number of seeds released each fall. The outer coating of the seeds produce butyric acid giving it a very pungent odor; yet, the underlying seed is used in Chinese cuisine.47. Umbrella tree, Magnolia tripetala (magnolia family; N)48. White spruce, Picea glauca (pine family; N)49. Thread cypress, Chamaecyparis pisifera (cypress family; I)50. Norway maple, Acer platanoides (maple family; I⊗)Norway maple is classified as a noxious weed and is invasive on our campus, as can be seen by the large number of seedlings in disturbed areas. Norway maples are more efficient at nutrient and water acquisition than our native maples, have higher net photosynthetic rates, and a longer growing season than their native competitors.51. Scholar tree, Styphnolobium japonicum (pea family; I)

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West along Loomis St.52. Callery pear, Pyrus calleryana (rose family; I⊗)53. Shagbark hickory, Carya ovata (walnut family; N)

Right to courtyard behind Hunt Hall.54. Flowering dogwood, Cornus florida (dogwood family; N)Flowering dogwood occurs from Maine to Florida and as far west as Texas and eastern Kansas. It has declined throughout its range due to dogwood anthracnose (Discula destructiva), an invasive fungal disease introduced to the U.S. in the 1970s. Plant pathologists have not yet been able to determine the native region of this fungus. A map of Bucknell trees from 1972 shows a large number of flowering dogwoods that are now absent. Many of these trees were undoubtedly killed by this disease.55. Bur oak, Quercus macrocarpa (beech family; N)Bur oaks have thick bark (exceeded only by Mediterranean cork oak) that allows them to survive frequent intense fires. They are one of the dominant trees of the oak savannas that once bordered the Great Plains from Texas to Canada.56. Japanese maple, Acer palmatum (maple family; I)

Exit courtyard between Vedder and Larison Halls.57. Saucer magnolia, Magnolia x soulangiana (magnolia family; I)

Return to St. George Street; turn left.58. Sweetgum, Liquidambar styraciflua (witch-hazel family; N)59. White fir, Abies concolor (pine family; N)60. Swamp white oak, Quercus bicolor (beech family; N)61. Kentucky coffeetree, Gymnocladus dioicus (pea family; N)62. White oak, Quercus alba (beech family; N) [no Arboretum plaque on tree]This is one of the oldest trees in Lewisburg (see the memorial plaque next to the tree).

South on 7th Street.63. Thornless honeylocust, Gleditsia triacanthos inermis (pea family; N) Most honeylocusts have large thorns that once protected the tree from now-extinct large mammals. Inermis is a thornless variety.

Left through passageway through Smith Hall.64. American hornbeam, Carpinus caroliniana (birch family; N)

Right to Walker St., across to south side of footbridge.65. Catalpa, Catalpa speciosa (trumpet-creeper family; N)700 species of predominantly tropical trees, shrubs, and vines make up the trumpet creeper family (Bignoniaceae). The family reaches its highest species density in South America and includes the genus Jacaranda, species of which have been introduced to tropical and sub-tropical regions throughout the world because of their spectacular ornamental value. Catalpa is one of the few members of the Bignonaceae that have evolved adaptations needed to survive outside the tropics and subtropics, and it retains a number of typically tropical characteristics including large showy flowers and large leaves with smooth margins and drip tips.Take path, left.66. Red pine, Pinus resinosa (pine family; N)67. Japanese zelkova, Zelkova serrata (elm family; I) The Japanese zelkova has a vase shape similar to the American elm and been used as a replacement for this native tree because it is also well adapted to urban conditions and is highly resistant to Dutch elm disease.

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68. Arbor vitae, Thuja occidentalis (cypress family; N)Cross 7th Street to Biology Building.69. Silver maple, Acer saccharinum (maple family; N)70. Crimson cloud hawthorne, Crataegus laevigata (rose family; I)71. American holly, Ilex opaca (holly family; N)72. European linden, Tilia europaea (linden family; I)73. Littleleaf linden, Tilia cordata (linden family; I)

End Tour

The Bucknell University Arboretum www.bucknell.edu/arboretum

Co-directors Mark Spiro (spiro@bucknell.edu), Biology Dept. Duane Griffn (dgriffin@bucknell.edu), Geography Dept.

Bucknell Facilities Staff Bill Kuntz, Certified Arborist John Testa, Grounds and Labor Supervisor Bill Zimmerman, Grounds and Labor Supervisor (retired)

Student Interns Ray Schlitt (’14) 2012Jack Ingram (’13) 2011Nick Gonsalves (’11), 2009 & 2010 Bobby Mullin (’11), 2010 Giorgina Alfonso (’12), 2009 Daniel Wang (’10), 2008 Internships provided by the Wayne E. and Margaret S. Manning Internship in the Botanical Sciences and have played integral roles in establishing the Bucknell University Arboretum and creating the Arboretum Walking Tour.

Collaborators Warren Abrahamson, Biology Dept Dina El-Mogazi, Environmental Studies Program & Environmental Center Michael Weaver, LIT Senior Instructional Technologist

November 27, 2012

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