Muscadine Grape (Vitis rotundifolia)
Mid September to Mid October
Muscadine is one of at least 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.
Hemlock (Tsuga canadensis and T. caroliniana)
Late September to Early October
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.
Flowering Dogwood (Cornus florida)
Mid October
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)
Mid October
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)
Mid October
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.)
Mid October
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. For general information about oaks, read "On the Prowl for Oaks", a Tree Fact article written by Richard Evans, UT Arboretum Director.
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.
Post Oak (Quercus stellata)
October
Post Oak, a small to medium sized tree, is mostly found along forest edges at the Arboretum. The heavy wood is resistant to decay and has a variety of uses such as railroad ties, mine timbers, and fence posts. Post Oak ranges from southern New England south to Florida and west to Kansas, Oklahoma, and Texas. It is tolerant of drought and is found on dry, sandy to rocky sites but also occurs on moister floodplains. In Texas and Oklahoma, Post Oak and Blackjack Oak are major components of the Cross Timbers - a dense forest of small trees forming the transition zone from forest to prairie grassland.
Its distinctive leathery leaves typically have five lobes, with the terminal three squarish lobes resembling a cross. The upper leaf surface is dark, shiny green in summer, while the lower surface is paler and covered with stellate (star-shaped) hairs. In the fall, leaves turn to a golden or bronze color.
The bark is similar to White Oak but not as flaky in older trees. The light to dark brown acorns are less than 1 in. length, with a cap covering about 1/3 of the nut.
Black Oak (Quercus velutina)
October
Black Oak is a common and important tree in the deciduous forests of our area, as reflected in the name of the ridge on which the City of Oak Ridge is built. Its range extends throughout much of the Eastern and Midwestern US. Black Oak leaves are quite variable and often difficult to differentiate from other members of the red oak group, such as Northern Red Oak. The leaves are from 4-10 in. long with 7-9 bristle-tipped lobes. Their upper surface is shiny green, while the lower is a paler green. Shade leaves have relatively shallow lobes, while sun leaves are more deeply lobed. As fall progresses, the leaves turn yellow to bronze and then red. Seeds mature over a two-year period, germinating in the spring after they fall. Seeds are an important food for wildlife such as squirrels, deer, and turkey.
The smooth, gray bark of young trees becomes dark gray to black with deep furrows as it matures. The grayish pubescent terminal buds tend to be square in cross section. The inner bark is orange to yellow in color (“pumpkin” color), which is a diagnostic feature for identifying Black Oak. A scaly cap covers 1/3 to 1/2 of the brown acorn at maturity.
Although the seeds contain bitter tannins, these can be leached with water. The powdered acorns have been used as a thickening for stews and as a flour. Acorns have also been roasted as a substitute for coffee. The dense wood is used for furniture, flooring, railroad ties, rough lumber, and fuel.
Chestnut Oak (Quercus montana)
October
Chestnut Oak, a member of the White Oak group, is a major component of the forest along the Lost Chestnut and the Oak Hickory trails and is frequently found elsewhere at the Arboretum. Chestnut Oak is typically found on dry, rocky sites, often in hilly or mountainous terrain and is also known as Rock Oak or Rock Chestnut Oak. It is not shade tolerant and may form almost pure stands. Its range in the US extends from southern Maine to Georgia, Alabama, and Mississippi and west to southeastern Michigan, southern Indiana and Illinois. In the east, it is best developed in the Appalachians and is uncommon on the coastal plain. The heavy wood is strong and durable and used for lumber and fuel.
Its common name reflects the resemblance of its leaves to American Chestnut - however, Chestnut Oak has rounded teeth around the leaf margin, while the leaves of American Chestnut have sharp teeth. In the fall the dark green leaves turn yellow-brown.
The relatively large, brown acorns (1.5 in long) have a cup that covers less than half of the acorn. Along with other oaks, they contribute to mast production providing an important source of food for wildlife. The dark, deeply ridged bark has a high content of tannins and has been used extensively for the tanning of leather.
Scarlet Oak
(Quercus coccinea)
October
At the end of October, the peak of fall colors is waning, and leaves are accumulating on the forest floor. The leaves of Scarlet Oak, one of the most colorful contributors to this fall display, turn bright red before falling. You can see this tree along our Arboretum trails. It is a member of the red oak group, with its sharply lobed, bristle-tipped leaves and deep, C-shaped sinuses extending close to the mid-vein — features distinguishing it from northern red oak and black oak. The swollen bases of many older trunks is caused by the same fungus that causes chestnut blight. Scarlet Oak ranges from New England, south along the Appalachians and Piedmont to Alabama and Georgia, and west to Michigan, Illinois, Missouri and Mississippi. The wood is used as lumber, flooring, and furniture. Its acorns are favorite food for deer, small mammals, and birds.
Hickories (Carya spp.)
Late October
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. For more information about hickories in general, read "Hickory Hunt", a Tree Fact article written by Richard Evans, UT Arboretum Director.
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) puts on its spectacular fall display in early November. 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 beautiful Ginkgo can be seen across the Arboretum entrance road from the Visitors’ Center, and another is located near the end of Marsh Road as it turns up to the Forest Loop Roads.
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, and no wild populations are known to exist. The tree is often referred to as a living fossil. Ginkgo is dioecious (i.e., meaning two houses) 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. Extracts from Ginkgo leaves have been used for medicinal purposes for many years.
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