Bald Cypress (Taxodium distichum)

Early September

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.

Resurrection Fern (Pleopeltis polypodioides)

Early September

Among the interesting ferns found at the Arboretum is the Resurrection Fern which can be observed on several Eastern Red Cedar trunks along the Cemetery Ridge Trail. It also occurs on rocky ledges off the trails. The fern is an epiphyte (or air plant) — a plant that uses another plant as a substrate but does not depend on that plant for food, nutrients, and water as does a parasitic plant.

During dry periods, the fern’s fronds appear shriveled. The common name is based on the fern’s ability to expand quickly (i.e., resurrect) in response to a rainy period, such as the rain we had at the end of August. The fern obtains its water and nutrients directly from rainwater and the wet bark or other substrate on which it grows. Resurrection Fern is widely distributed in Tennessee and the Southeastern U.S.

Honey Locust (Gleditsia triacanthos)

Early September

As you walk along Marsh Road, you will find two large trees with large thorns on their trunks. These Honey Locusts (or Sweet Locusts) have abundant yellowish, bean-like pods hanging down from the branches. The compound leaves are bi- or tri-pinnate (leaves divided two or three times). The native range of Honey Locust extends from central Pennsylvania south along the Appalachians to Alabama and west to Texas and the Central U.S.

Honey Locust belongs to the plant family Fabaceae (the bean or pea family). The large pods, which are yellowish now, turn brown as fall progresses and may persist into winter. The pods are sweet and eaten by cattle, hogs, and wildlife (thus the name "honey" or "sweet"), and the rattling of the seeds in the pods is said to resemble the singing of locusts (thus the second part of the common name).

The conspicuous thorns on the trunk and limbs are modified branches—they occasionally bear leaves. These have likely evolved over geologic time as protection against large herbivores. In the past, the very hard thorns have been used as nails, for carding wool, and as pins for closing sacks. The durable wood has been used for railroad ties, fence posts, and pallets. A number of thornless varieties have been developed for shade and ornamental use.

Eastern Red Cedar (Juniperus virginiana)

Early September

Eastern Red Cedar (also known as Old Field Juniper) is a small to medium sized coniferous tree with scale-like or awl-like leaves and bluish, berry-like fruits. It is widespread throughout the eastern U.S. and adjacent Canada. It invades open areas that have been disturbed by fire or cleared for agriculture. Areas dominated by Eastern Red Cedar are referred to as “Cedar Barrens” and are present in the Oak Ridge area. Eastern Red Cedar trees may persist in older forests for many years, and their presence may provide evidence of past land use for agriculture or other human or natural disturbance.

The female cones of Eastern Red Cedar develop into bluish “berries” with a waxy coating. These fruits are an important winter food source for birds, which disperse the seeds widely.

The aromatic wood repels insects and is used for lining cedar chests and as fence posts. The tree is also planted for windbreaks and used for making pencils and for Christmas Trees in the South. It is an alternate host for cedar-apple rust and should not be planted near fruit trees .

River Birch (Betula nigra)

Early to Mid September

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.

Hackberry (Celtis occidentalis)

Mid to Late September

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.

Fall Flowers

Mid to Late September

A walk along Scarboro Creek below the Magnolia Orchard and in the Marsh Area provides a good view of a variety of fall wildflowers along the stream banks. A sample of these are highlighted at left. Clockwise from upper left: Spotted Touch-Me-Not (Impatiens capensis), Cut-Leaf Coneflower (Rudbeckia laciniata), Turtlehead (Chelone glabra), Cardinal Flower (Lobelia cardinalis), Great Blue Lobelia (Lobelia siphilitica). Center: Sweet Joe-Pye Weed (Eupatoreum purpureum).

Persimmon (Diospyros virginiana)

Late September

Persimmon is a moderately sized tree growing to 60 feet tall and 2 feet in diameter. It is the most northern member of the Ebony family — other members of the family are tropical or subtropical. A Persimmon tree found just above the end of the Tulip Poplar Trail is currently loaded with orange fruit that will become deep purple as they mature during the next few weeks.

Persimmons are dioecious — meaning that male and female flowers are found on separate trees. The leaves and fruits of the tree are astringent, and have been described as puckery. However, when mature, the fruits lose their astringent tannins and become sweet and delicious. The genus name Diospyros can be translated from the Greek as ”food for the gods.”

Persimmon is native to the Eastern U.S. — New England to Florida, west to Texas, Iowa, and Kansas. The bark is dark brown to black and is deeply divided into small blocks. The dense wood has been used for such purposes as golf club heads and billiard cues.

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.

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