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.

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.

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.

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.

Hackberry, a member of the Elm family (Ulmaceae), is a tree found throughout much of the Eastern U.S. and adjacent Canada, south to Florida, and west through the Great Plains. It occurs on moist bottomland soils and somewhat drier sites with limestone derived soils. Several good examples of Hackberry can be seen along Arboretum trails. One is located near the start of the South Forest Loop Road just downhill from the entrance to the Cemetery Ridge Trail. There are also several Hackberries along the Heath Cove Trail, three at its entrance on the Valley Road, and another at the top of the loop before proceeding uphill to the Program Shelter.

Hackberry leaves are ovate in shape, being wide at the base and tapering to the tip. The leaf tip margins are toothed (serrate), and the leaf base tends to be asymmetrical. The light brown to gray bark of older trees is typically warty.

The dark orange to purple fruits ripen in September. (Note: This year there were few fruit produced on our Hackeberries.) These fruits are eaten and widely dispersed by birds (e.g., wild turkeys, grouse, and quail) and other wildlife. Sugarberry (Celtis laevigata), a closely related species, is hard to distinguish from Hackberry — one feature is that Sugarberry’s long leaves differ from those of Hackberry in having mostly smooth edges with few teeth.

A beautiful example of a River Birch cultivar (‘Heritage’) can be seen next to Scarborough Creek just below the Arboretum entrance. River birch is found throughout the Southeastern U.S. and ranges from southern New York and Pennsylvania, west to Indiana, and south to Texas and Florida. It is found on moist soils along stream banks, floodplains, and swampy bottomlands and can play an important role in stream bank erosion. It grows to heights of 50-75 ft and has alternate, doubly serrate (both fine and coarse teeth) leaf margins that are triangular in shape.

Its attractive, scaly, beige-colored bark is a conspicuous feature that makes River Birch desirable as a landscape tree. The knotty wood has limited value for lumber but is used for pulp and as firewood. Another native birch found at the Arboretum is Sweet Birch (Betula lenta), which is present at the junction of the North Loop Rd and Backwoods Trail, as well as at other places along our trails.

Bald Cypress is typically a Coastal Plains tree that is found in swamps and other wet areas. However, it is often planted in drier habitats where it thrives. Younger trees are pyramidal in shape and may grow up to 150 ft in height. It is a deciduous gymnosperm — the green needle-like leaves turn brown before being shed each autumn. The round green cones turn brown at maturity. At the Arboretum a number of Bald Cypress trees are planted in the Marsh Area, along Scarborough Creek, and in an area above the Program Shelter next to the Oak Collection.

A unique feature associated with Bald Cypress is the development of cypress knees, which are outgrowths from the root system that grow upward around the trees on wet sites. Although the function of these knees is unknown, it has been postulated that they facilitate gas exchange in the low oxygen environment of wetland habitats and/or provide support for the shallow-rooted trees. The decay-resistant wood has many uses in construction, such as docks, bridges, and buildings.

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.

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