Shrubs or small trees, 2-6 m tall. Branchlets pubescent, glabrous when old, with brown lenticels. Stipules caducous, deltoid, very small; pinnae 4-8 pairs, 5-9(-16) cm, rachis pubescent with black glands at location of lowest pinnae; leaflets 5-15 pairs, linear-oblong, 7-13 × 1.5-3 mm, main vein close to upper margin, base cuneate, margin ciliate, apex acute. Heads usually 1 or 2, axillary, 2-3 cm in diam.; peduncle 2-4 cm; bracts deciduous, pubescent. Flowers white. Calyx ca. 3 mm, outside glabrous at base, puberulent at apex, 5-toothed. Petals narrowly oblanceolate, ca. 5 mm, outside pubescent. Stamens 10, sparsely pubescent, ca. 7 mm. Ovary shortly stipitate, sparsely pubescent; stigma cupular. Legume straight, strap-shaped, flat, 10-18 × 1.4-2 cm, leathery, base attenuate, pedicel to 3 cm, pubescent, beak acute, hard. Seeds 6-25, brown, glossy, narrowly ovoid, flat, 6-9 × 3-4.5 mm. Fl. Apr-Jul, fr. Aug-Oct. 2n = 104*.
- Cultivated and naturalized in Fujian, Guangdong, Guangxi, Guizhou, Hainan, Taiwan, Yunnan [originally from tropical America, widely distributed in tropical and subtropical regions].
This plant is grown for use as green manure and fodder.