Natural History

Black Locust

Robinia pseudo-acacia, Legume family (Fabaceae)

Leaves:
Leaves are pinnately compound, 6 to 12 inches long. Each leaf has 7 to 19 leaflets. Leaflets are 1 inch long, ½ inch wide. Leaflets are elliptical with untoothed edges. Leaflets are dark blue-green above, pale below

Bark:
Bark is light gray, thick, deeply furrowed into long rough forking ridges

Twigs:
Each twig has a stout pair of thorns at its base.  Thorns are 1/2 inch long

Flowers:
Flowers are very fragrant, white, pea-shaped, grouped in showy drooping clusters, 4 to 8 inches long. Blooms in late spring.  Black locust trees are easily recognizable in late May and early June with their dense arrays of flowers.

Fruit:
Fruit is a long flat pod, dark brown, 2 to 4 inches long. Each fruit contains 3 to 14 dark brown flat beanlike seeds

Black locust leaves are larger and
rounder than Honey Locust leaves.
(photo source #7)