It was formerly included within a broader interpretation of the genus Sophora. The species of Styphnolobium differ from Sophora in lacking the ability to form symbioses with rhizobia (nitrogen fixing bacteria) on their roots. It also differs from the related genus Calia (mescalbeans) in having deciduous leaves and flowers in axillary, not terminal, racemes. The leaves are alternate, pinnate, with 9-21 leaflets, and the flowers in pendulous racemes similar to those of the Black locust.