Description from Flora of China
Annual or perennial herbs, twining. Stems pubescent or glabrous. Stipules triangular, 2-3.5 mm; leaflets ovate, 5-12 × 3-9 cm, lateral ones often oblique, sparsely pubescent along veins or glabrous on both surfaces, base rounded or broadly cuneate, apex acuminate or acute. Racemes axillary, 8-20 cm. Bracteoles elliptic, shorter than calyx tube, with 3 elevated veins when dry. Calyx campanulate, 2-3 mm, pubescent. Corolla white, yellowish, or reddish; standard 7-10 × 5-8.5 mm, apex emarginate; wings obovate; keel apex twisted for 1-2 turns. Ovary pubescent. Legumes falcate-oblong, 5-10 × 1.5-2.5 cm, compressed, apex beaked, 2-4-seeded. Seeds white, purple, or other color, subrhombic or reniform, 12-13 × 8.5-9.5 mm. Fl. spring to summer.
The seeds of this species are used for food.
Cultivated. Fujian, Guangdong, Guangxi, Hainan, Hebei, Hunan, Jiangxi, Shandong, Yunnan [native to tropical America; widely cultivated elsewhere].