Description from Flora of China
Hedysarum microphyllum Thunberg in Murray, Syst. Veg., ed. 14, 675. 1784; Codoriocalyx microphyllus (Thunberg) H. Ohashi; Desmodium microphyllum var. longipilum Ohwi; D. parvifolium Candolle; D. parvifolium f. yunnanense Pampanini.
Herbs, erect or prostrate, perennial, nearly glabrous. Leaves 3- or sometimes 1-foliolate; petiole 2-3 mm, when 1-foliolate 3-10 mm; leaflet blade narrowly obovate-elliptic or narrowly elliptic and 1-1.2 cm × 4-6 mm, or obovate to elliptic and 2-6 × 1.5-4 mm, both ends rounded. Racemes terminal or axillary, yellow-brown spreading pubescent, 6-10-flowered. Pedicel 5-8 mm. Calyx 5-parted; lobes linear-lanceolate, 3-4 × as long as tube. Corolla pink, nearly as long as calyx; standard obovate or obovate-orbicular, below middle attenuate, shortly clawed; wings obovate, auriculate and clawed; keel narrowly elliptic, longer than wings. Stamens diadelphous. Ovary pubescent. Legume ca. 12 × 3 mm, both surfaces shallowly dentiform, (2 or)3- or 4(or 5)-jointed; articles nearly orbicular, flat, minutely uncinate hairy and ciliate or glabrescent, reticulate veined. Fl. May-Sep, fr. Sep-Nov. 2n = 22.
The roots are used medicinally for reducing fever, relieving coughs, and dispelling phlegm.
One of us (Ohashi) considers this species as a member of Codoriocalyx, C. microphyllus (Thunberg) H. Ohashi (see J. Jap. Bot. 79: 109. 2004). This transfer is supported by molecular analysis, but here we follow the treatment in FRPS for convenience.
Wastelands, grasslands, thickets; 100-2500 m. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hubei, Hunan, Jiangsu, Jiangxi, S Shaanxi, Sichuan, Taiwan, Xizang, Yunnan, Zhejiang [Cambodia, India, Japan, Laos, Malaysia, Myanmar, Nepal, Sri Lanka, Thailand, Vietnam; Australia].