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Black Locust   arrow

Robinia pseudoacacia (Roe-bin-ee-a)
Family: Fabaceae, Pea

Key Steps


Black Locust leafLeaf: Oddly pinnate, 7-19 leaflets, egg-shaped, each leaflet 1 -2 inches long, smooth margins. Each leaf 6-14 inches long. Center vein is flat on upper surface, grooved and rounded beneath. Older foliage dark blue-green, new foliage bright yellow-green.

Bud: Tiny, may be completely submerged into stem. Rusty-colored hairs. 3-4 buds clustered, covered with overlapping scales. True terminal bud absent. Scales are brown outside, woolly inside.

Leaf Scar: Nearly circular. 3 bundle scars.

Stem: Hairless, reddish-brown, brittle, zig-zaggy. Ridges along stem from leaf scars. Pair of thorns at leaf axils.

Bark: Heavy, disorganized ridges.

Pith: Brown, solid.

Flower: Creamy white, fragrant clusters, 4-8 inches long. Pea-like blossoms, usually in clusters.

Fruit: 2-6 inch flat pods, thin, papery, reddish-brown, smooth. Persist through winter.

Habit: Irregular branching. Suckers. Can form a thicket.

Culture: Very adaptable.

Note: Young leaves, seeds, roots, and inner bark are poisonous.

Rose Locust (Robinia neomexicana) — Similar to Black Locust except flowers are lavender-rose and the fruit pods are smaller and have glandular hairs. Hairy flower stalks and hairy buds. Glandular, rusty hairs on stems. Naturalized.

Idaho Locust (Robinia. ‘Idaho’) — Lavender-rose flowers. More of a single-trunked tree form. Cultivated.