Trees of Wisconsin

Robinia pseudoacacia L.
black locust
Family: Fabaceae
tree branch leaf twig with thorns inflorescence flower fruit bark

Robinia pseudoacacia has alternate compound leaves with blunt entire leaflets. The paired, stout thorns at each node are unlike any other tree in our area except for Zanthoxylum americanum, which has pointed leaflets and is likely to be recognized as a shrub. Zanthoxylum also tends to have at least a few small thorns on the midrib of many leaves and Robinia has no thorns on the leaves. The buds of Robinia pseudoacacia are hidden beneath the bark of the twigs, but buds of Zanthoxylum are clearly visible. The flowers of Robinia pseudoacacia are white and very aromatic and the fruit is easily recognize as a legume. It is similar to Robinia hispida, but that species has prominently bristly branches and pink flowers.

The native range of Robinia pseudoacacia was from Arkansas and Missouri to Georgia and Pennsylvania, but it has been widely planted and it readily escapes into disturbed sites. It has been recorded throughout the state and it can cause serious problems as an invasive species.


known Wisconsin distribution


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