University of Tennessee Forest Resources Research Center

Two native species of Hemlock occur in East Tennessee. Eastern Hemlock is a wide ranging species in the Eastern U.S., and Carolina Hemlock is found only in the Southeast. Eastern Hemlock ranges from southern Canada south through the Mid-Atlantic states and the Appalachians to Alabama and Georgia and west to the Upper Midwest. In our region, Eastern Hemlock is typically found on northern or eastern exposures where the microclimate is cooler and moister than on surrounding topography or in the mountains above 2000 ft. Carolina Hemlock is often found on somewhat drier sites, although the two species may be found together in the same stand. Eastern Hemlock has shorter needles than Carolina Hemlock, and the needles tend to be in two ranks rather than spreading in all directions from the twigs.

The Hemlock Wooly Adelgid (Adelges tsugae), an invasive insect that is devastating hemlock forests throughout much of the Southeastern U.S., has been found on the Arboretum’s trees this spring. Although the insect is not evident in our trees at this time of year, it is likely to become manifest in coming years and will require treatment if the trees are to be preserved.

A unique plant at the Arboretum, Valentine’s Weeping Hemlock, is found near the Dwarf and Unusual Conifer Collection on the Main Drive. This plant was collected near Cosby, Tennessee, in 1940 by William L. Valentine and planted in his nursery. It was moved to the UT Arboretum in 1966. Children visiting the Arboretum love to climb under and around this unusual plant.

Chinese Chestnut (Castanea mollissima)

Late September to Early October

At this time of year, the ground below two Chinese Chestnut trees upslope from the Arboretum Visitors Center is littered with large spiny chestnut burs (up to 3 in. long and over 1 in. in diameter) that quickly open to reveal one to three dark brown nuts. These 20-year-old trees are resistant to chestnut blight which virtually eliminated American Chestnut from the Eastern Deciduous Forest of North America.

Chinese Chestnut cultivars are being crossed with American Chestnuts in efforts to develop a chestnut hybrid resistant to chestnut blight. Old stumps of American Chestnut can be seen along the Lost Chestnut Trail and elsewhere on the Arboretum. Sprouts from these stumps can occasionally be found, but they generally succumb to chestnut blight after a few years.

Muscadine Grape (Vitis rotundifolia)

Early to Mid October

Muscadine is one of three conspicuous grape species found at the Arboretum. The large twisted vines and distinctive leaves of the Muscadine grape are commonly seen along many of the Arboretum’s trails. Muscadine grapes flower in June and produce their tasty fruits in September and October (below left photo.) At this time of year, one can see the ripening deep purple to bronze fruit on vines which have climbed small trees or shrubs. The larger vines produce their fruit in the upper forest canopy making them more difficult to see. The fruity odor of the grapes often provides a clue to their presence in the canopy. Plants with a bronze or golden green fruit are commonly called scuppernongs. Muscadine is used in home-made wines and jellies and is an important wildlife food.

Both Fox grapes and summer grapes are also found along our trails. Fox grapes (above center photo) produce many smaller grapes in elongate bunches. This species has been hybridized with European grapes to provide resistance to a disease introduced from North America that devastated Europe’s vineyards in the 1860’s. Summer grapes (above right photo) have distinctive lobed leaves. These and the other grape species are a food source for birds and other wildlife.

Flowering Dogwood (Cornus florida)

The Arboretum hosts several research collections of dogwood. An extensive collection of dogwood species and cultivars near the Program Shelter provides researchers with genetic material to breed new dogwood varieties. Additional research collections of Flowering Dogwood (Cornus florida) and Kousa Dogwood (Cornus kousa) are found along the lower portion of Arboretum Drive where it merges with Old Kerr Hollow Road. The Arboretum also has an extensive research collections of Cornealian Cherry Dogwood (Cornus mas).

In the fall, Dogwood also provides red to mauve leaf colors and bright red fruits that are eagerly harvested by a variety of birds and squirrels.

Flowering Dogwood is most conspicuous in the spring with its bright flowers composed of four large white bracts surrounding the small yellow flowers.

Virginia Roundleaf Birch (Betula uber)

Virginia Roundleaf Birch at the Arboretum Visitors Center

A specimen of Virginia Roundleaf Birch, a rare native tree species, is planted in front of the Arboretum Visitor’s Center. The only known native population of this tree is in Smyth County in southwest Virginia. It was first collected in 1914 and then rediscovered in 1975. The U.S. Fish and Wildlife Service listed it as an Endangered Species in 1978, and initiated an extensive recovery program involving collection of seeds which were planted in a variety of sites. The recovery plan was sufficiently successful that in 1994 the status of the species was reclassified from Endangered to Threatened. It can now be found in arboreta and botanical gardens and is available to the public for planting.

This species has been considered a variety of Sweet Birch (Betula lenta) by some taxonomists. Sweet Birch is found along Arboretum trails (e.g., at the junction of the North Forest Loop Road Trail and the Backwoods Trail). Virginia Roundleaf Birch is a relatively small tree, reaching a height of 40 ft. The rounded leaves and dark bark have a wintergreen smell when crushed. The small cone-like fruit containing small nutlets are prominent on the tree at the Visitor’s Center in the fall.

Sawtooth Oak (Quercus acutissima)

Sawtooth Oak is a native tree of Japan, Korea, China, and the Himalayas that has been widely planted in the U.S. as a shade tree. It is considered a good tree for wildlife because it produces large crops of acorns, but it has also been identified as being a potentially invasive species in some areas.

Sawtooth Oak grows quickly, reaching heights of 40 to 50 feet. Its distinctive dark green leaves are oblong to lance-shaped and have bristle-tipped teeth along the leaf margin. The dark brown, oval shaped acorns are covered by a cap with spreading reflexed scales resembling hair. The gray-brown bark is ridged and deeply furrowed.

Several Sawtooth Oaks are found in an oak collection area along Arboretum Drive, and one labeled tree is located at the end of Marsh Road near its junction with the Forest Loop Road.

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 (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 (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.

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.

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.

Hickories (Carya spp.)

A variety of hickories occur in the Arboretum forests. Identifying a tree as a hickory is relatively easy - it has alternate, compound leaves (several leaf blades associated with each axillary bud) with 5 to 9 leaflets. Identifying the species of hickory, however, is more challenging and often requires determining characteristics of the leaves, hickory fruits (outer husks and nuts), the terminal buds, and the bark. Furthermore, there is considerable variation of these characteristics within a species and hybridization of species produces individuals with intermediate or mixed characteristics. Three of the more common hickories found at the Arboretum are described below.

Pignut Hickory (C. glabra) leaves typically have 5 to 7 glabrous leaflets (i.e. without hairs). The pear-shaped to ovoid fruits are about 1 inch in diameter, with thin husks and nuts that are not ribbed. The bark is relatively tight, has vertically oriented ridges that are rounded, and may be flaky.

Mockernut Hickory (C. tomentosa) has leaves with 7 to 9 leaflets that are pubescent on the undersides. The globular to oval fruits are about 1 1/4 inches in diameter, with thick husks and a 4-ribbed nut. The tight bark has flat to rounded, interlaced ridges.

A few Shagbark Hickories (C. ovata) are found along our trails. Their leaves usually have 5 essentially glabrous leaflets. The 1 1/2 inch diameter fruit has a thick, rounded husk that splits all the way to the base, and a nut ridged on 4 sides. The distinctive bark is broken into long, shaggy plates.

Japanese Larch (Larix kaempferi)

Late October to Early November

As you walk through the Arboretum’s Marsh Area in late October/early November, you may notice a tall conifer with leaves changing from green to bright yellow. This Japanese Larch is native to central and northern Japan. It is planted in Japan and northern Europe (including the British Isles) where its decay resistant wood is used for construction and fences. It is also the most popular of the larches for use in Bonsai. Japanese Larch can grow to more than 100 feet in height with spreading branches that give it a cone-shaped appearance.

First-year shoots bear single leaves (needles), while older branches bear clusters of needles (up to 60 per cluster) on short shoots. Japanese Larch is one of several deciduous conifers at the Arboretum — others include Dawn Redwood (Metasequoisa glyptostrboides), Bald Cypress (Taxodium disticum), and Pond Cypress (Taxodium ascendens). Typically larches are trees of mountains or high latitudes. Three species of larch are native to North America: Tamarack (Larix laricina) is a component of boreal forests and peatlands in Canada and the northern U.S., extending south into Ohio, Pennsylvania, and West Virginia; Western Larch (L. occidentalis) occurs in the Northwestern U.S. and adjacent Canada; and Subalpine Larch (L. lyalli) grows at or near timberline in the mountains of the Pacific Northwest.

Ginkgo (Ginkgo biloba)

Late October to Early November

Ginkgo (or Maidenhair Tree) is putting on its spectacular fall display. For a short period its leaves turn bright yellow, and then almost overnight they fall to the ground creating a conspicuous leaf shadow under the tree's spreading branches. A well-developed Ginkgo can be seen across the Arboretum entrance road from the Visitors' Center. Several Ginkgos can also be seen in the Shade Tree Study Area near the Program Shelter.

Ginkgo is a Gymnosperm — its developing ovules and seeds are not enclosed in an ovary. Its fan-shaped leaves resemble those of Maidenhair Fern (hence its common name) and have dichotomous (forked) venation. Ginkgo is well-represented in the fossil record. For thousands of years it only survived in temple gardens in China. The tree is often referred to as a living fossil. Ginkgo is dioecious with separate male and female trees. The male trees are most commonly planted because the female trees produce fruits with a strong, malodorous odor. Ginkgos are hardy trees that are planted in many parts of the U.S. and elsewhere.

Hemlock (Tsuga canadensis and T. caroliniana)

Chinese Chestnut (Castanea mollissima)

Muscadine Grape (Vitis rotundifolia)

Flowering Dogwood (Cornus florida)

Virginia Roundleaf Birch (Betula uber)

Sawtooth Oak (Quercus acutissima)

White Oaks (Quercus spp.)

Hickories (Carya spp.)

Japanese Larch (Larix kaempferi)

Ginkgo (Ginkgo biloba)