Description from Flora of China
Herbs. Stems twining, slender to slightly robust, pubescent. Leaves pinnately 3-foliolate; stipules small, triangular, ca. 6 mm, deciduous; petiole 4-12 cm, sparsely pubescent; stipels small, bristlelike; petiolules 3-5 mm, densely pubescent; terminal leaflet rhomboid-circular, oblate-circular, or rarely subtriangular, 5-9.5 × 4.5-10 cm, papery, pubescent, with sparse light yellow glands, basal veins 3, base almost truncate or slightly cordate, apex abruptly caudate-acuminate; lateral leaflets much smaller, obliquely ovate. Raceme axillary, to more than 20 cm, ca. 20-flowered, rachis densely villous. Flowers ca. 2 cm. Calyx campanulate, ca. 5 mm, pubescent; lobes triangular to lanceolate, unequal, lower one longest. Standard circular, with accessory substance; keels inflexed, shorter than standard and longer than wings. Ovary 2-ovuled. Legume oblong or obovate-oblong, 2-3 × ca. 1 cm, compressed, green, apex with small curved mucro, densely villous, usually with constriction between seeds. Seeds 1 or 2, purplish black or dark brown, suborbicular, compressed, 5-7 mm wide; hilum short, circular. Fr. Sep-Oct.
● Rocky mountains; 1100-1300 m. Yunnan (Mengzi).