Additional Resources

National Register Big Trees

Ohio State Plant Facts

What Tree Is It?

America's forestry movement actually started in Ohio with the creation of the American Forestry Association in Cincinnati in 1875.

Division of Forestry
2045 Morse Rd.
Building H1.
Columbus, OH 43229

A deciduous tree from the Bean Family (Fabaceae)

Black Locust was once native to the southern Appalachian region of the Eastern United States, but has now spread throughout the world, including all of Ohio. It is valuable as an aggressive, rapidly growing invader species that controls erosion in road cuts, abandoned fields, strip-mined areas, logged forests, and fireswept areas. Initially colonizing by seeds, it also suckers from the roots, forming pure stands and snuffing out competitive weeds and woody plants. Trees of sufficient size are valued for their logs, which make fine fenceposts, poles, or railroad ties due to the anti-rotting properties of the olive-green wood.

Black Locust can quickly grow to 50 feet tall by 25 feet wide, when found in the open. However, high winds coupled with several diseases and pests often limit its potential height. As a member of the Bean Family, it is related to Redbud, Honeylocust, Kentucky Coffeetree, and Wisteria, as well as other Locusts.

Planting Requirements - Black Locust prefers soils that are rich, deep, moist, well-drained, and of variable pH, in full sun to partial sun. However, it is often found under poor soil conditions, especially soils that are thin and near limestone outcrops. It tolerates salts and other pollutants in its water (including strip mine runoff), salt spray on its bare bark in winter, and air pollution. It can grow almost anywhere in zones 4 to 8, provided that it is not near wet soils or shady conditions.

Potential Problems - Black Locust has a long list of potential pests (locust borer can be fatal, and leaf miner can make a tree aesthetically unpleasing by mid-summer) and pathogens (bark canker and trunk rot are the worst) that can make this tree unsightly, unhealthy, or in serious jeopardy on some occasions. In general, Black Locust as a colony survives to be a group of fairly sizable trees, unless the land on which it grows is cleared.

Leaf Identification Features

Black Locust has alternate, pinnately compound leaves that have blue-green leaflets with smooth margins and undersides that are silvery-gray. The tips of each leaflet may be slightly notched, rounded, or slightly pointed.

Trees have an upright growth habit throughout their life, and have a medium-fine texture when in summer foliage. Fall color is chartreuse at best, and often blue-green then abscising. Some premature leaf drop may occur during dry summers.

Other Identification Features

The perfect, white, pendulous flowers of Black Locust occur in mid- to late spring and are sweetly fragrant. Individual flowers have the typical look of a Bean Family member and cover the canopy of the tree when most other ornamental trees have long since spent their blooms.

The small fruit pods of Black Locust may shatter by mid-summer, or hang on the twigs throughout much of the winter. Prickles occur primarily on stout juvenile twigs and branchlets, originating from young trees, vigorous new growth from established trees after pruning, or from root suckers.

The brown to gray twigs of Black Locust are zigzag, and cast a crooked outline against the winter sky. Smooth branchlets soon become fissured into crisscrossing flat ridges, which become tall, sinewy-like ridges on mature bark, separated by deep furrows.

Bark color ranges from gray to brown, with olive green tints.