Description from Flora of China
Annual or perennial herbs, erect, trailing, or twining. Stems 1-3 m, subglabrous. Stipules lanceolate, ca. 1 cm, with a narrow spur below point of attachment; leaflets ovate-rhomboid, 5-15 × 4-6 cm, lateral ones oblique, puberulent or glabrous on both surfaces, base acute to rounded, apex acute. Racemes axillary, with 2-6 flowers clustered at top of rachis. Calyx campanulate, 6-10 mm; teeth lanceolate. Standard yellowish white or violet, suborbicular, 1.2-3.3 × 1-3.2 cm, apex emarginate; wings blue to purple, subdeltoid; keel usually white or pale, not twisted. Legumes terete, 7.5-30(-90) × 0.6-1 cm. Seeds several, dark red or black, mottled with black or brown, oblong or reniform, 6-12 mm.
Widely cultivated in China [native to Africa and Asia; widely cultivated in tropical and subtropical regions].