Description from Flora of China
Crotalaria macrophylla Willdenow, Sp. Pl. 3: 982. 1802; Flemingia congesta Roxburgh ex W. T. Aiton; F. ferruginea Wallich ex Bentham; Maughania ferruginea (Wallich ex Bentham) H. L. Li; M. macrophylla (Willdenow) Kuntze.
Shrubs, erect, 0.8-2.5 m tall. Young branches densely adpressed silky villous. Leaves digitately 3-foliolate; stipules lanceolate, up to 2 cm, villous, with glandular striations, apex long acuminate, usually deciduous; petiole 3-6 cm, narrowly winged; petiolules 2-5 mm, densely hairy; leaflets papery to thinly papery; terminal leaflet broadly lanceolate to elliptic, 8-15 × 4-7 cm, glabrous except for veins, abaxial surface with small dark brown sessile glands, basal veins 3, base broadly cuneate, apex acuminate; lateral leaflets smaller, oblique, base rounded at one side, cuneate on other. Racemes usually clustered at axil, 3-8 cm, with many clustered flowers; peduncle usually extremely short. Calyx campanulate, 6-8 mm, shortly very pale brown villous; lobes linear-lanceolate, ca. 2 × as long as tube, lower one longest. Corolla purple, slightly longer than calyx; standard oblong, shortly clawed, auriculate; wings narrowly elliptic, slenderly clawed, one with auricle; keel oblong, long clawed, apex slightly curved. Ovary elliptic, with very pale brown hairs. Legume elliptic, 10-16 × 7-9 mm, sparsely pubescent, apex with small acute beak. Seeds 1 or 2, glossy black, orbicular. Fl. Jun-Sep, fr. Oct-Dec. 2n = 22.
The glands on the fruit are separated after drying and are used as a purple or orange dye.
Disturbed meadows, roadsides, forest margins; 200-1800 m. Fujian, Guangdong, Guangxi, Guizhou, Hainan, Jiangxi, Sichuan, Taiwan, Yunnan [Bangladesh, Bhutan, Cambodia, India, Indonesia, Laos, Malaysia, Myanmar, Nepal, Thailand, Vietnam].