Description from Flora of China
Annual herbs, 30-80 cm. Taproot to 80 cm, fibrous roots lateral. Stem erect, terete, branched. Leaves 3-foliolate; stipules entire, membranous, base adnate to petiole, apex acute; petiole spreading, 6-15 mm; leaflets narrowly obovate, ovate, to oblong-elliptic, terminal equal to laterals, 15-40 × 4-15 mm, sparsely pubescent or glabrescent abaxially, glabrous adaxially, lateral veins 5 or 6 pairs, base cuneate, margin dentate in upper 1/2. Flowers sessile, axillary, solitary or in pairs. Calyx 7-8 mm, villous. Corolla creamy or pale yellow, base violet, 13-18 mm. Ovary puberulent; ovules numerous. Legume long conical, 7-12 × 0.4-0.5 cm, straight or slightly curved, glabrescent, veins longitudinally reticulate, apex with long beak to 2 cm, distal suture thickened. Seeds 10-20, brown, oblong-ovoid, 3-5 × 2-3 mm, surface uneven. Fl. Apr-Jul, fr. Jul-Sep.
The seeds are used medicinally. The tender leaves and stems are used as vegetables; and the dried stems, leaves, and seeds are used as flavoring for foods and in baking. The dried plant also is used as insect repellent.
Cultivated throughout China, escaped in fields as a semi-wild weed in Gansu, Hebei, Heilongjiang, Liaoning, Nei Mongol, Ningxia, Qinghai, Shaanxi, Shanxi, Sichuan, Xinjiang, Xizang [Himalayan region; SW Asia].