Description from Flora of China
Herbs, 45-60 cm tall. Stems lianescent, sparsely villous. Leaves pinnately 3-foliolate; stipules ovate-lanceolate or ovate-triangular, 5-13 mm; petiole 2.8-11.5 cm; stipels linear or linear-lanceolate, 3-7 mm; petiolules short, 1-2 mm; leaflets elliptic to ovate-elliptic, 2.5-11 × 1.5-5 cm, thinly papery, abaxially sparsely villous or sometimes glabrous, adaxially glabrous, lateral veins 7-11 pairs, obviously convex abaxially, base rounded, apex obtuse or acute, rarely acuminate, with mucro. Peduncle with 4 or 5 or more bracts at base; bracts ovate to ovate-lanceolate, 2-4 mm. Flowers axillary, usually solitary, 2.5-5 cm; bracteoles similar to bracts but larger, 4-8 mm. Calyx large, tubular, membranous, usually glabrous, 5-lobed; lobes lanceolate to ovate-lanceolate, ca. 1/4 as long as to equal to tube, apex acuminate. Corolla light blue or purple, 2.5-5 cm; standard broadly elliptic or almost obovate, base acuminate; wings and keels similar and subequal, much shorter than standard, with slender claws. Ovary and style villous. Legume linear-oblong, 2.5-10 × 0.5-0.8 cm, apex beaked, both ventral and dorsal sutures with ribs. Seeds 2 to many, dark brown, almost cylindric or reniform. Fl. May-Sep, fr. Sep-Jan.
Shrubs, roadsides, forests; 100-2000 m. Guangxi, Yunnan [Bhutan, India, Laos, Myanmar, Thailand, Vietnam; North America].