black locust
Robinia pseudoacacia
  • LEAVES: alternate, deciduous, pinnately compound;
    7-21 leaflets, each 1/2-2” long; bases of petioles and leaflets swollen; stipular spines
  • FLOWER: white, 6-8” long raceme of paplionate (pea-like) flowers; 5 petals: 1 is enlarged (standard), 2 wings, 2 fused to form the “keel"; flowers in spring after leafing-out: easiest time of the year to identify this species
  • FRUIT: legume, 2-4” long, flat; hard, kidney-shaped seeds
  • TWIGS: stout, zigzag; stipular spines; submerged lateral buds (remember:  thorns are modified branches, spines are modified leaves or stipules)
  • BARK: furrowed and fibrous on older trees
  • FORM: medium-sized tree, 40-60 feet tall x 1-2 feet diameter; often poor form (especially on poor sites), and short-lived
  • HABITAT: moist, rich, well-drained sites
  • WETLAND DESIGNATION: Obligate Upland (UPL): Almost never occurs in wetlands of the Atlantic and Gulf Coast Plain Region
  • RANGE: Ozarks and Appalachians; naturalized throughout much of the eastern US; one of the most widely-planted trees worldwide; now common in Europe
  • USES: very durable wood; accumulates silicon which is hard on saw blades; used for fence posts, erosion control; nitrogen fixer; good honey tree; minor use of seed by squirrels and quail; browse by deer
  • Best Recognition Features:
    1. pinnately compound leaf; never bipinnately compound
    2. stipular spines
    3. 2 to 4 inch-long flat legume