University of Tennessee Forest Resources Research Center

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.

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.

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.

Chinese Chestnut (Castanea mollissima)

Muscadine Grape (Vitis rotundifolia)

White Oaks (Quercus spp.)

Hickories (Carya spp.)

Ginkgo (Ginkgo biloba)