An intolerant, medium-sized tree found on a variety of sites with very dense, rot-resistant wood, poisonous inner bark and nitrogen-fixing root nodules. Its native range is restricted to the central Appalachians and Ozarks, but is naturalized throughout eastern North America and parts of the west. Leaves are deciduous, alternate, and pinnately compound. Leaflets are elliptical-ovate, entire, dull, and dark blue-green. Twigs are relatively stout, usually with prominent stipular spines. Minute naked lateral buds are often superposed and submerged beneath the leaf scar. Fruit is a flat, brown legume, 2-4" long. Bark becomes reddish-brown to nearly black and is deeply furrowed.