Oxydendrum arboreum, the sourwood or sorrel tree, is the sole species in the genus Oxydendrum, in the family Ericaceae. It is native to eastern North America, from southern Pennsylvania south to northwest Florida and west to southern Illinois; it is most common in the lower chain of the Appalachian Mountains. The tree is frequently seen as a component of oak-heath forests.
The bark is gray with a reddish tinge, deeply furrowed and scaly. Branchlets at first are light yellow green, but later turn reddish brown. The wood is reddish brown, with paler sapwood; it is heavy, hard, and close-grained, and will take a high polish. Its specific gravity is 0.7458, with a density of 46.48 lb/cu ft.
The winter buds are axillary, minute, dark red, and partly immersed in the bark. Inner scales enlarge when spring growth begins.
Leaves are alternate, four to seven inches long, 1.5 to 2.5 inches wide, oblong to oblanceolate, wedge-shaped at the base, serrate, and acute or acuminate. Leaf veins are feather-veined, the midrib is conspicuous. They emerge from the bud revolute, bronze green and shining, and smooth; when full grown, they are dark green, shining above, and pale and glaucous below. In autumn, they turn bright scarlet. Petioles are long and slender, with stipules wanting. They are heavily laden with acid.