Black Locust

Latin name: Robinia pseudoacacia

Etymology: The genus Robinia is named after the 17th century French botanist Jean Robin. The species name is a combination of the Latin words for ‘false’ (pseudo) and ‘Acacia’ (acaia), as its’ leaves are resembling those of the Acacia genus.

Family: Fabaceae (Legumes)

Origin: Appalachian Mountains from Pennsylvania to Alabama and the Ozark region

Native habitats: Black Locust is typical of young woodlands and disturbed areas with high light conditions and dry soils.

Black locust is a native tree rarely seen in the forest, but often found around dwellings, including historic houses. In the Princeton area, Clark House, Brearley House, and Veblen House all have towering black locusts nearby. The tree bears abundant white flowers for pollinators, but most extraordinary is the tree’s wood. It burns hot and clean in woodstoves, and is highly resistant to rot, making it ideal for fenceposts, including around Veblen House. Fallen black locusts here have been milled for use in building a boardwalk.

Description: Black Locusts have a height of between 70-80 feet and a diameter of 2-3 feet. Leaves are once-compound with 6-20 egg-shaped leaflets. They measure between 6-12 inches. The mature bark is dark, deeply ridged and crosshatched, twigs are hairless. Strong paired thorns, measuring between 0.5 and 1 inches, flank nearly circular leaf scars, through which white, hairy buds burst upon enlargement. Flowers are white, fragrant and appear in clusters between May and June. Fruits are 2-6 inches long, flat pods that appear from September until April.

Similar species: Other locusts within the Robinia genus have bristly, glandular or hairy twigs. Honey locust has large branched unpaired thorns.

Wildlife value: Black Locust is a larval host plant for several butterflies and the flowers are a great source of nectar for bees. Buds and catkins are eaten by birds and rabbits consume the sprouts and seeds during the winter.

Uses: The yellow, coarse grained wood is hard, strong, and naturally rot resistant and is often used to make fence posts and rails, mine timbers, and landscaping ties. Black locust honey is commercially sold.