Description from Flora of China
Crotalaria akoensis Hayata; C. kawakamii Hayata; C. sinensis J. F. Gmelin.
Herbs, 15-60 cm tall, brownish yellow pilose except for legumes. Stems terete, branched at base. Stipules absent. Leaves simple, subsessile; leaf blade variable in shape, usually lanceolate, linear-lanceolate, linear, or oblong-linear, 2-3.5 × 0.4-1 cm, abaxially densely brown coarsely pilose but more densely so on veins and along margin, adaxially glabrous or sparsely pilose, base attenuate, apex acuminate. Racemes congested on branch apices, 1-5-flowered or with 1 or 2 flowers in axils; bracts lanceolate, 3-5 mm. Pedicel 2-4 mm; bracteoles inserted at base of calyx tube, similar to bracts. Calyx 2-lipped, 8-10 mm, parted to base; abaxial 3 lobes linear to linear-lanceolate; adaxial 2 lobes broadly lanceolate. Corolla pale yellow, included in or ± as long as calyx; standard ovate to orbicular, 7-9 mm, base with 2 appendages; wings oblong, 7-9 mm; keel narrowed apically from middle and extended into a twisted beak. Ovary subsessile. Legume cylindric, 0.8-1.2 cm, included in or exserted from calyx, 15-20-seeded. Seeds cordate, ca. 2.5 mm, smooth. Fl. Jun-Oct, fr. Sep-Dec.
Montane grasslands; below 100-1000 m. Fujian, Guangdong, Guangxi, Hainan, Hunan, Jiangxi, Taiwan, Yunnan [Cambodia, India, Indonesia, Laos, Malaysia, Myanmar, Nepal, Papua New Guinea, Philippines, Thailand, Vietnam].