Description from Flora of China
Hedysarum prostratum Linnaeus, Mant. Pl. 1: 102. 1767, not Indigofera prostrata Willdenow (1802); I. dominii Eichler; I. tsiangiana F. P. Metcalf.
Shrublets or perennial herbs, usually prostrate, sometimes ascending, 20-90 cm tall. Stems with appressed medifixed subsymmetrically 2-branched trichomes. Stipules ovate, 3-4 × ca. 2 mm, apex acuminate. Leaves 1.5-3 cm, 5-9-foliolate; petiole and petiolules with appressed medifixed trichomes; stipels not visible; leaflet blades alternate, obovate to narrowly obovate, 5-10(-15) × 2-3(-5) mm, both surfaces with medifixed 2-branched trichomes, secondary veins not visible, base cuneate, apex obtuse to truncate and with a ca. 0.1 mm mucro. Racemes 0.5-2.5 cm, sessile; bracts ovate to triangular, 2-2.5 × ca. 1 mm. Pedicels, bracts, and calyces with medifixed trichomes. Pedicel ca. 0.5 mm. Calyx 2-2.5 mm, with appressed medifixed trichomes; tube ca. 1 mm; teeth narrowly triangular, 1-1.5 mm. Corolla red; standard red to orangish red, broadly ovate to orbicular, 3-4.5 × 2.5-4 mm, outside hairy; wings 3-4 × 1-1.5 mm, glabrous, margin shortly ciliate; keel 3-4 × ca. 1.5 mm, glabrous, margin shortly ciliate, lateral spur ca. 0.5 mm. Stamens 2.5-4 mm; anthers glabrous. Ovary densely strigose, with (1 or)2 or 3 ovules. Legume oblong, straight, spreading, 3-8 × 1.5-2 mm, densely hairy, apex slightly beaked; endocarp not blotched. Seeds (1 or)2 or 3 per legume, dark brown, cubic, ca. 1 × 1 mm. Fl. Jun-Nov, fr. Nov-Dec. 2n = 16, 32.
The name Indigofera enneaphylla Linnaeus has been incorrectly applied to this species. As now lectotypified, this name is an illegitimate synonym of Psoralea pinnata Linnaeus.
Sandy ground near rivers or seashores, dry open places, sunny trailsides; 100-700(-1200) m. Hainan, S Sichuan, Yunnan [India, Indonesia, Laos, Myanmar, Nepal, Pakistan, Papua New Guinea, Sri Lanka, Thailand, Vietnam; Australia].