University of Tennessee
Forest Resources AgResearch and Education Center
Plants W

Walking Fern (Asplenium rhizophyllum)

Walking FernWalking Fern Sori One of the most interesting ferns present at the Arboretum is the Walking Fern, typically found on moss covered, calcareous rocks in shady microhabitats. It occurs at scattered sites around the Arboretum and adjacent research areas, but is not obvious along our trails. This unique fern characteristically forms circular patches with its lance-shaped, undivided, evergreen leaves tapering to slender points arching over the mossy substrate. Where the tips touch the moist substrate, they may develop roots and new plants - thus "walking" across the substrate. The brown linear sori (spore-bearing structures) are borne on the undersurface of the leaves, more or less paralleling the network of veins. Research suggests that Walking Fern may require an exposed rock surface to become established. This member of the Spleenwort family (Asplenaceae) is found throughout eastern North America, from southern Ontario and Quebec, south to Florida, Georgia, and Mississippi, and west to Oklahoma, Kansas, Iowa, Wisconsin and southeastern Minnesota. It is known to occur throughout eastern and middle Tennessee.

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Water Oak (Quercus nigra)

Marsh Area Water Oak 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.

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Western White Fir (Abies concolor)

Western White Fir Western White Fir Needles Western White Fir Branches

Western White Fir (also known as Rocky Mountain White Fir, Colorado White Fir or simply White Fir) is native to the Oregon Cascades, the California Sierra's, and the Rocky Mountains from southern Idaho south to Arizona, New Mexico, and northern Mexico. A specimen of this species planted in 1966 can be seen in the Conifer Collection on the slope to the north of Arboretum Drive. In California it may grow as high as 140-180 ft, but in the Rockies its maximum height is on the order of 125 ft. Western White Fir has silvery blue-green, blunt tipped needles, 2-3 inches long, that curve upwards when mature. The gray to silvery-white bark is smooth in younger trees, but becomes deeply fissured in older ones. The seed cones are borne upright, a distinguishing characteristic of firs.

Native Americans used Western White Fir for such medicinal purposes as treating rheumatism, pulmonary problems, sores and boils, and cuts. Extracts have been shown to have anti-tumor activity, and resin collected from the bark was purportedly used to fill tooth cavities. The wood is used for plywood, paper pulp, crating, furniture, and to a limited extent for construction. Western White Fir is also a popular Christmas tree.

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

White Baneberry (Doll's Eyes) Flower

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.

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White Oak (Quercus alba)

White Oak Tree White Oak Leaf 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.

White Oak Buds White Oak Acorns 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.

White Oak Bark White Oak Bark 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.

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White Oaks (Quercus spp.)

Several types of white oaks are producing abundant acorns this year. The acorn production (mast) from these oaks provides an important food for such animals as deer, squirrels, turkeys, and bears. The acorns of white oaks need 1 year to mature; red oaks require 2 years. White oaks have lobed leaves or ones with rounded teeth, while red oaks generally have sharp-lobed, bristle-tipped leaves.

White Oak Acorns White Oak Leaf White Oak (Q. alba) is one of the most common oaks found along Arboretum trails. Its acorns, which occur in clusters of two or three, are often green when they first fall but at maturity are a rich brown.

Chestnut Oak Acorns Chestnut Oak Leaf Chestnut Oak (Q. montana) is also common along our trails and is especially conspicuous along the Lost Chestnut Trail. The large (up to 1 1/2 in.) acorns have a thin, warty cap and are shiny and brown to black at maturity.

Post Oak Acorns Post Oak Leaf Scattered individuals of Post Oak (Q. stellata) are found at the Arboretum. Typical leaves are broader at the top and often resemble a cross. The relatively small acorns (up to 3/4 inch long) are covered for 1/3 to 1/2 their length by a bowl-shaped cup.

Bur Oak Acorns Bur Oak Leaf The range of Bur Oak (Q. macrocarpa) extends into northwestern Tennessee, but is centered in the Midwest. Several individuals are found in the Oak Collection near the Program Shelter. Bur Oak has broad spatulate leaves and produces large acorns (up to 2 inches long) with a distinctive fringed cup.

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Wild Comfrey (Cynoglossum virginianum)

Comfrey Plant Comfrey Flower Comfrey Fruit
If you were walking along the South Forest Loop Road or the Cross Roads Trail in early April, you may have noticed numerous rosettes of broad green leaves emerging on the deciduous forest floor. By late April these plants developed a flower stalk with several clasping leaves, terminating in a small cluster of white to light blue flowers. By mid-May, the bristly fruits, covered with many "hooks" that adhere to ones clothing or to an animal's fur, are well developed. Wild Comfrey, a member of the Boraginaceae plant family, is found throughout the eastern US. Extracts from its roots were used by the Cherokees to treat a variety of ailments, and the leaves have been used to smoke like tobacco. The genus name, Cynoglossum, comes from the Greek referring to the leaf shape resembling a dog's tongue. Cynoglossum officinale, a related species introduced from Europe is commonly called Hound's Tongue. It has reddish flowers and is considered an invasive species in many western states.

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Winged Sumac and Smooth Sumac
(Rhus copallinum and Rhus glabra)

Winged Sumac Flower Winged Sumac Berries Winged Sumac Fall Leaves

Winged Sumac (R. copallinum) is one of two common species of sumac found in our area. It has large pinnately compound leaves with petioles that have "wings" - flattened blade-like structures - running along the leaf stalk between the leaflets. The flowers appear in June, and the dull red to purple fruits are well-developed by September. The leaves turn bright red in the fall.

Smooth Sumac Red Flowers Smooth Sumac Flower Smooth Sumac Bark

Smooth sumac (R. glabra) differs from Winged Sumac in having toothed leaflets and no wings along the leaf axis. The bark of Smooth Sumac has distinct lenticels but lacks dense pubescence that is characteristic of other species of Sumac. The fruits of both these species provide a food source for many birds and small mammals. Other members of this genus include Staghorn Sumac (R. typhina) and Fragrant Sumac (R. aromatica).

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Winter Fruits

As one walks the Arboretum trails in late December and early January, the fruits of a variety of woody plants and vines can be seen. Our native Dogwood, American Holly and Greenbriar are found along with several non-native, invasive plants, such as Oriental Bittersweet, Chinese privet, and Amur Honeysuckle. Some of these fruits, such as those of the Dogwood provide food for a variety of birds (e.g., robins, cedar waxwings) and small mammals. Six of the more common winter fruits found at the Arboretum are described below.

Flowering Dogwood Fruit Oriental Bittersweet Fruit

Left: Flowering Dogwood (Cornus florida)
Right: Oriental Bittersweet (Celastrus orbiculatus)
American Holly Fruit Chinese Privet Fruit

Left: American Holly (Ilex opaca)
Right: Chinese Privet (Ligustrum sinense)
Amur Honeysuckle Fruit Greenbriar species Fruit

Left: Amur Honeysuckle (Lonicera maackii)
Right: Greenbriar species (Smilax sp.)

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Winter Jasmine (Jasminum nudiflorum)

Winter Jasmine Flowers As we progress through the month of March, our anticipation for discovering spring flowers rises. Meanwhile, a few winter-blooming plants such as Winter Jasmine must satisfy our thoughts of spring. This spreading shrub blooms in early February near the Program Shelter and will continue to flower sporadically throughout March. Its bright yellow tubular flowers extend from the axils of the green, angled stems and appear before the leaves come out.

Winter Jasmine Shrub Winter Jasmine was originally imported from China to Britain in the 1840s. It provides a good ground cover, particularly on sloping ground or raised structures where it can cascade downward. It is often mistaken for Forsythia, but blooms earlier and for a longer period. It can also be readily distinguished by its green shoots and spreading habit.

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University of Tennessee - Forest Resources AgResearch and Education Center
901 South Illinois Avenue, Oak Ridge, Tennessee 37830 · Telephone: 865-483-3571 · Email: UTforest@utk.edu