Black Locust

Robinia pseudo-acacia

Fabaceae (Legume family)


Black locust is an introduced tree up to 50 feet tall that often forms colonies by root sprouts. Spines on the young stems are unbranched and resemble large rose thorns. Seven to 19 oval leaflets are arranged opposite with the entire leaf up to 6 inches long.

The fragrant, abundant flowers have white petals and a banner with a yellowish center and are arranged in hanging clusters 4 to 8 inches long. The pods are flat, thin and brown and may persist through the winter.


Black locust is extensively planted in shelterbelts and as an ornamental. It can be found in all areas of Texas except the Rolling Plains and the Trans-Pecos. It is probably native to the southeastern United States.

Toxic Agent

The toxic agent of black locust is robin, a protein toxin. All parts of the plant except the flower are toxic.

Horses, cattle, sheep and poultry have been poisoned.

Horses are most often poisoned and are the most susceptible species. Horses that consumed as little as 0.04 percent of their weight in bark showed signs of poisoning in 1.5 hours.

Signs of Livestock Ingestion

Signs of poisoning are similar in all species and may include: Anorexia; Depression; Diarrhea; Weakness (posterior paralysis in cattle and horses); Cold extremities; Weak pulse; Irregular heartbeat.

In fatal cases, death usually occurs within 1 or 2 days.

Management Strategies

Most clinically affected animals recover after removal from the source. However, complete recovery may take several weeks, and horses often founder or develop laminitis. Do not place horses in a paddock with a black locust tree. Boredom may cause them to consume the leaves or strip the bark from the trees.