Black Locust

Robinia pseudoacacia

twig, fruit, and leaf Leaves are alternate, compound, with thorns or spines.

branchThe black locust's natural range extends from Pennsylvania southwestward to Alabama and westward to southern Illinois. The tree often suffers extensive damage from the locust borer insect.

The leaves are pinnately compound with 11 to 15 leaflets 1 to 1-1/2 inches long, rounded at both ends and with smooth margins.

The twigs are crooked and angular with short, stout, single, unbranched thorns, one-half inch long.

branchThe fruit is a dark, red-brown, flexible pod 3 to 4 inches long, containing small, reddish brown beanlike seeds.

flowers, pod, bark, and twigsOn young branches the bark is smooth and greenish to brown in color. On older branches and trunks it is broken into a network of coarse, deep ridges and is gray to gray-brown in color.

Leaves: pinnately compound; margin entire

Branching: alternate

Bark: mature trees reddish brown to nearly black, deeply furrowed. Bark is poisonous; cattle die from browsing on bark and children become ill from chewing on twigs or bark.

Height: 70 to 80 ft.

Trunk Diameter: 2 to 3 ft.

Longevity: 60 to 80 yrs.

Tolerance: intolerant

Range: east of Rocky Mountains

Fun Facts:

  • Wood is resistant to rot and used to make railroad ties and fence posts.
  • Fruit, pod (legume) eaten by wildlife.


Identify Another Tree

This key was developed by "bt" in June 1982. It was put into HTML format by Stephen Ostermiller in July 1997. Copies of the entire guide in zip format that may be taken to camp on a laptop are available to those who write.