Black locust is a legume with root nodes that, along with bacteria, "fixes" atmospheric nitrogen into the soil. These soil nitrates are usable by other plants. Most legumes have pea-like flowers with distinctive seed pods. Black locust is native to the Ozarks and the southern Appalachians but have been transplanted in many northeastern states and Europe. The tree has become a pest in areas outside its natural range. You are encouraged to plant the tree with caution. Read more on Invasive Exotic Trees.
1. The Silviculture of Black Locust
Black locust (Robinia pseudoacacia), sometimes called yellow locust, grows naturally on a wide range of sites but does best on rich moist limestone soils. It has escaped cultivation and become naturalized throughout eastern North America and parts of the West.
Forestryimages.org provides several images of parts of black locust. The tree is a hardwood and the lineal taxonomy is Magnoliopsida > Fabales > Fabaceae > Robinia pseudoacacia L. Black locust is also commonly called yellow locust and false acacia.
3. The Range of Black Locust
Black locust has a disjunct original range, the extent of which is not accurately known. The eastern section is centered in the Appalachian Mountains and ranges from central Pennsylvania and southern Ohio, south to northeastern Alabama, northern Georgia, and northwestern South Carolina. The western section includes the Ozark Plateau of southern Missouri, northern Arkansas, and northeastern Oklahoma, and the Ouachita Mountains of central Arkansas and southeastern Oklahoma. Outlying populations appear in southern Indiana and Illinois, Kentucky, Alabama, and Georgia
Leaf: Alternate, pinnately compound, with 7 to 19 leaflets, 8 to 14 inches long. Leaflets are oval, one inch long, with entire margins. Leaves resemble sprigs of grapes; green above and paler below.
Twig: Zigzag, somewhat stout and angular, red-brown in color, numerous lighter lenticels. Paired spines at each leaf scar (often absent on older or slow growing twigs); buds are submerged beneath the leaf scar.