University of Tennessee Forest Resources Research Center

As you walk to the end of Marsh Road, look to the right for a dense thicket of Devil’s Walking Club that exhibits large terminal clusters of creamy white flowers and large compound leaves. This relatively small tree gets its name from the club-shaped branches and the “vicious” prickles along the trunk, especially at the nodes. The prickles only form during the first year of growth, and as the tree matures the older stems gradually lose their prickles.

Leaves are doubly or triply compound and may be up to 5 feet in length, with individual leaflets 2-4 inches long. The purple to black fruits mature in late summer and early fall and are eaten and dispersed by birds; the foliage may be browsed by deer. Devil’s Walking Stick is native to the southeast, but has been successfully introduced to many other parts of the eastern U.S.

American Hornbeam (Carpinus caroliniana)

Late July to October

American hornbeam (also known as ironwood, muscle-wood, blue beech) grows abundantly along Old Kerr Hollow Road. At this time of year the maturing fruit clusters hang down from the canopy. These consist of a 4-6 inch stalk with a series of 3-lobed, leaf-like bracts — the small nutlets are found at the base of these bracts. A related tree, European Hornbeam, is found along the Heath Cove Trail.

Common names of this tree are related to its bark and wood. The dense wood dulls woodworking tools (ironwood) and takes a horn-like polish (hornbeam). The muscle-like bark has sinewy, muscle-like ripples, (muscle-wood) and its otherwise smooth, blue-gray appearance resembles beech bark (blue-beech). The wood has been used for tool handles, bowls, and ox yokes. The fruits and buds are eaten by birds, squirrels, and deer. This understory tree occurs along streams and other low areas throughout the eastern U.S.

Black Walnut (Juglans nigra)

Black Walnut, a relatively common tree at the Arboretum, is readily recognized by its large, pinnately compound leaves with 11-23 leaflets, its dark (almost black) ridged to platy bark, and its green (turning to yellow), ball-shaped fruits. It is considered a pioneer species invading fields and other open areas where it grows rapidly.

Black Walnut is an allelopathic plant, producing a chemical compound, hydrojuglone. When hydrojuglone is oxidized in air or soil, it becomes the toxic chemical juglone. This toxin (produced from the leaves, fruits, and roots) accumulates in the soil under the tree, inhibiting the growth of most other plants. A few plants, especially grasses, are unaffected by juglone and can grow under the tree canopy.

Black Walnut is a highly prized wood. Early settlers used it extensively for construction, but today it is primarily used for making furniture and gunstocks. The nuts are used in cooking, the oily husks have been used to make dyes and walnut stain, and the pulverized shells are used in oil drilling, cleaning jet engines, and for making activated charcoal.

The presence of black walnut trees at various sites around the Arboretum often indicates the location of former home sites. The fruits from these trees appear to be somewhat larger than normal, perhaps reflecting a selection by the homeowners of more vigorous cultivars.

White Oak (Quercus alba)

White Oak, a dominant tree of the eastern deciduous forest, is found along many of the Arboretum trails and in the Oak Collection near the Program Shelter. It grows to heights of 100 ft, with a canopy spread that may be 50-80 ft wide. Its light green leaves have 7-9 rounded lobes and are from 4-7 in. long. White Oak ranges from Maine and adjacent Canada south to northern Florida, Georgia, and Alabama, and west to Minnesota and Texas. White Oak provides important food and cover for many birds and mammals. An important lumber tree, it is used for furniture, whiskey barrel staves, and many other purposes.

The broadly oval buds are reddish brown and have no pubescence. Large crops of acorns are produced periodically - a single tree may produce 10,000 to over 20,000 acorns. The acorns have shallow caps that are smooth underneath. They do not exhibit dormancy but germinate shortly after they fall to the ground with the root penetrating the soil in the fall, but the shoot not developing until the following spring.

The light-gray bark is typically divided into long broad scaly plates or ridges. On large trees the bark is often broken into scaly broad plates and smooth patches may be evident.

White Baneberry (Doll's Eyes) (Actaea pachypoda)

A small population of White Baneberry is present near the lower end of the Oak-Hickory Trail. The white fruits with a dark center (the basis for the common name Doll’s Eyes) are evident in early August. The small white flowers borne on a terminal stalk appear at the end of April or early May, and the white fruit, which is initially green, matures in August. The large alternate, pinnately compound leaves have sharply toothed leaflets. The fruit and other parts of the plant are poisonous (the basis for the common name Baneberry). A member of the Ranunculaceae plant family, Actaea pachypoda is found in forests throughout eastern North America from southern Canada to northern Florida, and west to Nebraska and Kansas.

American Beautyberry (Callicarpa americana)

American Beautyberry is a native shrub found in the Southeastern US from Maryland to Florida, and west to Oklahoma and Texas. An excellent specimen of this plant can be seen in front of the Arboretum’s Visitors Center. The pink flowers develop along the stem at the leaf nodes in early August. After pollination, the fruits develop as dense ball-like clusters of green drupes. These mature later in the fall into conspicuous purple fruits that may persist well into the winter months. The fruits provide a source of food for a variety of birds.

Water Oak (Quercus nigra)

A good example of a Water Oak is present near the last bridge going into the Marsh Area from Marsh Road. Water Oak, a native of the Southeastern U.S., is mainly associated with the Coastal Plain and Piedmont, but extends into the southern and western portions of Tennessee — the UT Vascular Plants Database shows records of Water Oak in Knox and Roane Counties as well. (Click here to reach the UT Vascular Database )

It is a member of the red oak group, with at least some of the leaves having bristle tips. The leaves are variable in shape but most typically are spatulate (shaped like a spatula or spoon). Water Oak is usually associated with bottomland habitats along water bodies, but it does not tolerate prolonged seasonal flooding. Its acorns are eaten by many animals, and it is used extensively in the South as a shade and street tree in urban settings.

Black Alder (Alnus glutinosa)

European Black Alder, a native species of Europe, western Asia, and northern Africa, is also known as Common Alder or Black Alder. It has been widely planted in the U.S. and has become naturalized in the Northeast, the Midwest, and Maritime Canada. As with other species of alder, European Black Alder does well on wet sites such as stream banks and wetland situations, but it can also grow on drier sites where the soils are infertile. It is used for reclamation of strip mines because it can grow rapidly to help control erosion, and its nitrogen-fixing root nodules and abundant leaf litter improve soil fertility. It provides cover and a dependable food source for seed-eating birds during the winter.

The leaves readily distinguish it from other alders in being rounded to obovate — the sticky leaves and twigs are the basis for the specific name "glutinosa."

A European Black Alder in the Arboretum’s Marsh Area has been listed as a Tennessee State Champion Tree based on its girth, height, and crown.

Tree-of-Heaven (Ailanthus altissima)

Tree-of-Heaven, a native of China, was first imported to Europe in the 1740’s and subsequently was widely planted in many European cities. It was brought to the US in the 1780’s and was planted as a street tree in many eastern cities because it is tolerant of smoke and soot and can thrive in poor soils. It gradually became naturalized and spread throughout much of North America. It is considered to be invasive in at least 30 states, including Tennessee where it is ranked as a ‘Severe Threat’ by the Tennessee Exotic Pest Plant Council. Tree-of-Heaven has alternate, very large (1-3 ft long), pinnately compound leaves with leaflets that have one or more glandular teeth near the base and no other teeth along their margins - a feature that distinguishes it from species of Sumac, Ash, and Black Walnut, all of which have teeth around the entire leaflet margins. This tree grows rapidly and reaches heights of 80-100 ft. It is dioecious, with small, pale yellow to greenish male and female flowers usually being borne on separate trees. It produces large numbers of flat, twisted, winged fruits, each with a single central seed. Its prolific production of seeds and its ability to sprout readily from roots after being cut back account for its invasive character. In addition, it is reported to produce toxic chemicals that inhibit the growth of other plants in its immediate vicinity. Tree-of-Heaven is not abundant at the Arboretum but is commonly seen along roads and greenways in the Oak Ridge area.

Downy Rattlesnake Plantain (Goodyera pubescens)

Downy Rattlesnake Plantain, one of our more common orchids, can be found throughout the year. Its basal rosette of dark, blue-green, rounded leaves have a distinctive network of silver veins with a broad stripe down the center of each leaf. These leaves are present throughout the winter and have been reported to persist up to four years. The entire plant is covered with a downy pubescence. The upright inflorescence of small white flowers appears in late July or early August.

This species of Goodyera is found throughout the eastern US and adjacent Canada. In our area it is most commonly seen in dry upland pine and oak woodlands with acid soils. The mottled leaves, which somewhat resemble plantain, a common weed, are also said to resemble a snake’s skin. Some have claimed that the plant can be used as a cure for snakebite. The dried inflorescence, which may persist into the following growing season, also resembles the rattles of a rattlesnake. Take your pick for the basis of the ‘rattlesnake’ portion of the common name!

Cardinal Flower (Lobelia cardinalis)

As you walk through the Arboretum’s Marsh Area in August, you are likely to see a number of bright red flowers growing along the edge of Scarborough Creek. Cardinal Flower is one of nine species of the genus Lobelia that occur in Tennessee (Visit the UT Herbarium web site for more information about the other species in Tennessee.) Lobelia cardinalis is our only Lobelia with brilliant red flowers — however, one other red-flowered species (L. laxiflora) is found in southern Arizona. Cardinal Flower is found throughout eastern North America and adjacent Canada, and across the southwest to California. Its typical habitat is along streams, ponds, and other wetland situations.

The two-lipped, tubular flowers have three prominent lobes on the lower lip and two smaller lobes on the upper lip. Hummingbirds and butterflies are major pollinators. The common name is purportedly a reference to the bright red robes of Roman Catholic Cardinals. Although the plant has been used for a variety of medicinal purposes, its extracts contain as many as 14 poisonous alkaloids. A planting of Cardinal Flowers is present next to the Arboretum’s Visitor Center.

Elms (Ulmus spp.)

Four native species of Elms are found in East Tennessee — American Elm, Winged Elm, Slippery Elm, and Rock Elm. Beginning in the 1930’s, Dutch Elm Disease, caused by a fungus, has greatly reduced the populations of these trees. American Elm, once the major shade tree in towns throughout the Midwest and East, has been virtually eliminated by this pathogen. Three species of elm found along Arboretum trails are briefly described below.

Winged Elm (Ulmus alata) is a relatively small tree growing to heights of 40-50 ft. Distinguishing characteristics include relatively small (1½ - 3½ inches long), narrow, coarsely toothed leaves and thin, corky ridges along many of its branches - the wings that are the basis for its common name. Winged elm is found along the lower parts of Cemetery Ridge Trail.

Slippery Elm (Ulmus rubra) is fairly common along Old Kerr Hollow Road. The leaves are up to 7 inches long, and their upper surface is rough, feeling like sandpaper. Its common name refers to the fact that its inner bark has a very slippery, mucilaginous sap. If you scratch a leaf petiole and run a finger along the split, you can feel its slipperiness. Slippery Elm grows to heights of 60-70 ft.

Rock Elm (Ulmus thomasii) is present along the upper portions of Cemetery Ridge Trail and the South Forest Loop Road. Its leaves are relatively smooth in texture and 2-4 in. long. Rock Elm is also called Cork Elm because of the irregular corky wings that develop on older branches. It can grow to heights of 100 ft. Although present in East Tennessee, Rock Elm is more common in middle Tennessee. In our area, it is typically found on relatively dry, rocky sites.

Hollow Joe Pye Weed (Eupatorium fistulosum)

Great Spangled Fritillary Butterfly on Joe Pye Weed

Hollow Joe Pye Weed, a member of the Aster Family with a head of pink disk flowers (no ray flowers), can be seen along Scarboro Creek near the Arboretum entrance. This type of Joe Pye Weed (also called Trumpet Weed) grows up to 10 ft in height and can be distinguished from similar Eupatorium species by its purplish colored, hollow stems, and whorls of 4-7 simple leaves at each node of the stem. This plant is attractive to many insect pollinators such as butterflies, bees, and wasps.

Other types of Joe Pye Weed include Sweet-scented Joe Pye Weed (E. purpureum), a more northern species with solid green stems and 3-4 leaves at each node, and the smaller Spotted Joe Pye Weed (E. maculatum), with spotted purple, solid stems and flat-topped flower heads.

Various accounts have identified Joe Pye as an Algonquin Indian or a white man who used the plant for treating typhus. The hollow stems were used as straws and blow guns. The plant was also used for a variety of internal and external medicinal uses. Apparently there is little, if any, scientific support for its medicinal values. Hollow Joe Pye Weed is found in moist areas along streams, ditches, and roadsides, and in upland fields and meadows.

Black Gum (Nyssa sylvatica)

Mid to Late August

Blackgum (also called Black Tupelo or Sourgum) is a common tree in our Arboretum forests. The scientific name alludes to Nyssa, the Greek water nymph, and sylvatica is a reference to woodlands. The origin of the common name “Blackgum” is unclear but may refer to the dark blue-purple fruit. The shiny, alternate leaves are usually elliptic in shape, often wider above the middle with a pointed tip, and from 2-5 in. long. In the fall they turn red, orange, or almost purple.

The branches grow out perpendicular to the trunk, somewhat resembling the spokes on a wheel, and older branches tend to droop. The trees are either predominately male or female, but often a few flowers of the opposite sex are present. The small, dark blue fruits (drupes) are found in the fall — this year our trees appear to be bearing few, if any, fruits. The fleshy fruit is eaten by birds, squirrels, and other small mammals, while young leaves provide forage for deer. The tree may grow to heights of 60-100 ft., and can live to be over 400 years old.

Northern Catalpa (Catalpa speciosa)

Two large Northern Catalpa trees (also known as Indian Bean Tree or Cigar Tree) are found near the Juniper Collection, east of the Arboretum Program Shelter. The genus name Catalpa purportedly comes from a Cherokee Indian word for “bean tree” — the seed pod, which is conspicuous at this time of year, has a long, bean-like shape. Catalpa belongs to the Bignoniacea family, which also includes Cross Vine and Trumpet Creeper.

The natural range for Northern Catalpa includes western Tennessee and other parts of the Central Mississippi Valley. It has been widely planted in urban areas and on farms to provide materials for fence posts. The showy white flowers that give rise to the elongate seed pods appear in late spring.

Southern Red Oak (Quercus falcata)

Southern Red Oak is one of several red oak species at the Arboretum. The red oaks have sharply lobed leaves that are bristle-tipped and their acorns require 2 years to mature. Other common native red oaks occurring here include Black Oak (Q. velutina), Scarlet Oak (Q. coccinea), Northern Red Oak (Q. rubra), and Blackjack Oak (Q. marilandica). Red oaks differ from white oaks in having rounded leaf lobes or teeth without bristle tips and acorns that require only 1 year to mature. Southern Red Oak has distinctive alternate leaves which are shiny on the upper surface and rusty colored pubescent on the underside. Leaves on mature trees are deeply divided with long, sharply pointed lobed tips and 2-4 curved side lobes that are bristle-tipped. The leaf base tends to be rounded and resembles a turkey foot. Young trees may have bell-shaped leaves with 3-5 rounded bristle-tipped lobes. These leaves often resemble those of Blackjack Oak.

The dark bark has scaly ridges separated by deep narrow furrows. The acorns are orange-brown at maturity and their caps cover 1/3 or less of the nut. The acorns are important food for wildlife, and the wood is used as lumber for many purposes.

A closely related species, Cherrybark Oak (Q. pagoda) has been considered a variety of Scarlet Oak, but it is now recognized as a separate species. It is typically found along coastal plains in the Eastern U.S., while Scarlet Oak occurs on drier upland sites throughout the Southeast.

Devil's Walking Stick (Aralia spinosa)

American Hornbeam (Carpinus caroliniana)

Black Walnut (Juglans nigra)

White Oak (Quercus alba)

White Baneberry (Doll's Eyes) (Actaea pachypoda)

American Beautyberry (Callicarpa americana)

Water Oak (Quercus nigra)

Black Alder (Alnus glutinosa)

Tree-of-Heaven (Ailanthus altissima)

Downy Rattlesnake Plantain (Goodyera pubescens)

Cardinal Flower (Lobelia cardinalis)

Elms (Ulmus spp.)

Hollow Joe Pye Weed (Eupatorium fistulosum)

Black Gum (Nyssa sylvatica)

Northern Catalpa (Catalpa speciosa)

Southern Red Oak (Quercus falcata)