Pignut Hickory (Carya glabra)
Pignut Hickory (Carya glabra) is one of several hickory species found in our Arboretum forests. It is found throughout the Eastern U.S. and north into southern Ontario. It is one of the most common hickories in the Appalachians. The common name was given by early settlers because the abundant nuts provided food for free-ranging hogs. It’s alternate, compound leaves typically have 5 (occasionally 7) glabrous leaflets (i.e., without hairs) that are finely toothed. The pear-shaped to ovoid fruits are about 1" in diameter, with thin husks and nuts that are not ribbed. A distinctive feature of the fruit is that when mature, the husk only splits about half-way along the fruit axis. The bark is relatively tight, has vertically oriented ridges that are rounded, and may be flaky. The nuts, which are high in crude fat and have moderate content of proteins, calcium and phosphorus, are an important food for a variety of mammals, such as squirrels, chipmunks, and black bear, as well as some birds such as turkeys, woodpeckers, pheasants and several songbirds. The strong, hard, tough wood is used for making tool handles, fence posts, sporting goods, agricultural implements, and as fuel wood. Early settlers used thin splits of the wood to make brooms.
Sourwood (Oxydendrum arboreum)
Sourwood is a small to medium-sized tree found along many Arboretum trails. It ranges from Pennsylvania, Ohio, and Indiana, south to northwest Florida, Alabama, Mississippi, and Louisiana. As a member of the Heath Family (Ericaceae), it is related to such plants as blueberries, rhododendrons, and azaleas. The white, bell-shaped flowers are borne in terminal one-sided clusters and appear in late June and July. The fruits mature in late summer and persist on the flower stalks, often into fall and winter. Because the flowers are often near the top of the trees, they may be difficult to see under a forest canopy. The finely toothed leaves, 5-8 in. long, turn a yellow to crimson red in the fall. A good place to observe these trees in bloom is a Sourwood study plot just below the Arboretum’s Elmore Holly Collection.
The ridged and often deeply furrowed bark of Sourwood is readily identified especially in older trees where it becomes distinctly blocky. Trees may grow 50-60 ft high, with trunks that are often bent or leaning. The common name comes from the sour taste of the leaves and twigs. Leaves and bark of Sourwood were used by Native Americans and early settlers to treat a variety of ailments such as mouth ulcers, asthma, indigestion, and kidney and bladder ailments. Sourwood has little timber value, but the heavy wood has been used for handles, fuel wood, and specialty items. Sourwood honey is a favorite of many.
Dawn Redwood (Metasequoia glyptostroboides)
Dawn Redwood is a deciduous conifer with flat, needle-like leaves that turn a copper-colored brown in November. A specimen of this tree, planted in 1965, can be seen in the Arboretum’s Central China Collection near the end of Marsh Road. Dawn Redwood is related to Bald Cypress (Taxodium distichum) of the southeastern U.S. and to California’s Redwood (Sequoia sempervirens) and Giant Sequoia (Sequoiadendron giganteum).
In the early 1940s, a Chinese paleobotantist recognized that fossils initially thought to belong to the genus Sequoia, should be reassigned to a new genus, Metasequoia. In 1945, living individuals of Metasequoia glyptostroboides were found in the Sichuan Province of China. Extensive field surveys in the late 1940s found this “living fossil” present in limited populations in both Sichuan Province and neighboring Hubei Province. Propagation of seeds and cuttings at arboreta in the U.S. and elsewhere resulted in Dawn Redwood becoming available for planting. Although Dawn Redwood does not have wide-spread commercial value, its lumber is similar to that of Coastal Redwood and has been used to make furniture as well as pulp for making plyboard and composite materials.
Metasequoia is a fast growing tree — some of the oldest U.S. trees (planted in 1948) have attained diameters of over 1 meter. Dawn Redwood can be distinguished from Bald Cypress by several characteristics — the buds develop on the underside of the branches not along the tops; the leaves are opposite, not alternate; the base of the trunk is fluted and buttressed; and the branches have rounded depressions below their junction with the trunk. The light brown pollen cones are borne on long stalks appearing in early spring; the inconspicuous female cones are borne singly.
Invasive Shrubs, Vines, and Trees
Invasive plants are non-native species that aggressively invade areas and displace native species. These plants may have been introduced by gardeners or transported from other countries by accident. Examples of invasive shrubs, vines, and trees commonly encountered at the Arboretum are shown below. These species are listed in the “Severe Threat” category by the Tennessee Exotic Pest Plant Council (tneppc.org/invasive_plants) and present management challenges as well as research opportunities. More detailed descriptions of these can be found by clicking on the individual links below.
View a list of Previously Featured Plants
Please help us preserve our natural heritage!
No collecting of plant materials is permitted at the UT Arboretum.