Tall tree with dark bark. Normally the bark is adorned with long, stout, branched thorns that make tree-hugging very risky, however, in Wildwood we have the variety inermis, which has no thorns. Leaves divided into numerous pairs of small, narrow, oval, untoothed leaflets, with a pair at the end. Sometimes the leaflets then divided into still smaller leaflets. Flowers are small, greenish, in long clusters in late spring. Fruits are leathery pods with thick seeds bulging out the sides. The pods curl and twist into bizarre shapes.

Believed to be originally native only to the Mississippi River Valley, but spreading, especially with the help of humans. We have at least two trees in Wildwood, near the entrance, one under the cliffs east of the gate and the other next to the parking lot behind the bank. Since they are of the unarmed variety they probably persist from cultivation.

The fruits are unmistakeable and provide easy identification. When not in fruit, the the untoothed leaflets can distinguish it from most other trees with many leaflets. Black locust (Robinia pseudo-acacia) is most similar, but that tree has larger leaflets and small thorns on the branches.