Description from Flora of China
Dolichos purpureus Linnaeus, Sp. Pl., ed. 2, 2: 1021. 1763; D. albus Loureiro; D. lablab Linnaeus.
Herbs, twining. Stems to 6 m, usually purplish. Stipules lanceolate; leaflets deltoid-ovate, 6-10 × 6-10 cm, lateral ones oblique, base subtruncate, apex acute or acuminate. Racemes axillary, erect, 15-25 cm. Flowers 2-5 clustered at each node. Calyx ca. 6 mm, upper 2 teeth wholly connate, lower 3 subequal. Corolla white or purple; standard orbicular, ca. 12 mm; wings with blade ca. 10 mm; keel base attenuate. Ovary linear; style longer than ovary. Legumes oblong-falcate, 5-7 × 1.4-1.8 cm, compressed, straight or slightly curved, beaked. Seeds 3-5, white, purple, or purple-black, oblong; hilum linear. Fl. Apr-Dec.
This species is edible and is used medicinally.
Widely cultivated in China [native to Africa; cultivated throughout the tropics].