Description from Flora of China
Trees or shrubs, all parts (excluding corolla) sometimes with glandular bristles. Buds only axillary. Stipules bristlelike or spinelike. Leaves imparipinnate; leaflet blades petiolulate and stipellate, margins entire. Racemes axillary, pendulous; bracts membranous, caducous. Calyx campanulate, 5-lobed, adaxial 2 lobes subconnate into an apical lip. Corolla white, pink, or rosy; petals stipitate; standard large, retroflexed; wings curved; keel incurved, blunt. Stamens diadelphous, 1 distinct from other 9 connate ones; anthers homomorphic, 2-loculed, longitudinally dehiscent. Ovary stipitate, many ovuled; style subulate, apically piliferous; stigma small, terminal. Legume compressed, narrowly winged along ventral suture, segments often with appressed bristles. Seeds oblong or obliquely reniform, strophiole absent.
Between four and ten species: North America and Central America; two species (both introduced) in China.