Description from Flora of China
Herbs, perennial, suffrutescent, 2-4 m tall. Branches pubescent, glabrescent, internodes often 0.5-2.5 cm, nodes conspicuously gibbous. Stipules triangular-lanceolate, 3-4 mm, caducous, pubescent. Leaves 20-40-foliolate; petiole and rachis appressed pubescent, more so at petiole base; rachis 4-10 cm; petiolules appressed pubescent; stipels acerose; leaflet blades oblong to linear, 1.3-2.5 cm × 3-4(-6) mm, both surfaces with purplish black glands, abaxially sparsely appressed pubescent when young but glabrescent, adaxially glabrous or glabrescent, midvein evident on both surfaces, base obliquely rounded, apex rounded to retuse and mucronate. Racemes 4-10-flowered; peduncle 8-10 cm, slender, pubescent, glabrescent; bracts linear-lanceolate, caducous, abaxially sparsely appressed pubescent. Pedicel ca. 8 mm, slender, pubescent when young; bracteoles smaller than bracts, caducous. Calyx campanulate; teeth shortly triangular, inside appressed pubescent to glabrescent. Corolla yellow or calyx and standard purplish black and wings and keel partly purplish black or red; standard transversely elliptic, 1.1-1.3 cm, wider than long, with a 4-5 mm claw, with a S-shaped callus ca. 2 mm, basally decurrent to lamina, widened in middle, and distinct and acuminate to obtuse at apex, base subcordate, apex emarginate; wings oblong, 1-1.2 cm, with a curved ca. 4 mm claw, base inconspicuously auriculate, apex rounded; keel nearly semicircular, 6-8 × 5-7 mm, lamina base narrower than apex and with a triangular short auricle, claw ± as long as calyx. Stamen tube 8-10 mm; anthers ellipsoid. Ovary glabrous; style ca. 5 mm, glabrous; stigma globose. Legume contorted when young but straight or slightly curved at maturity, subterete, 15-23(-30) cm × 3-4 mm, ca. 5 mm between transverse septa, base often with a marcescent calyx, apex beaked. Seeds 20-40 per legume, subterete, 3-4 × ca. 2 mm, slightly compressed; hilum rounded and concave. 2n = 12, 24.
Cultivated and sometimes naturalized in wastelands, roadsides, riversides, mountain slopes, streamsides; below 300-1300 m. Guangdong, Hainan, Taiwan, Yunnan [origin uncertain; cultivated throughout the tropics].