30. Indigofera tinctoria Linnaeus, Sp. Pl. 2: 751. 1753.
木蓝 mu lan
Shrublets, erect, 50-100 cm tall. Young branches with appressed white medifixed symmetrically 2-branched trichomes. Stipules narrowly triangular, ca. 2 mm. Leaves 2.5-11 cm, 9-13-foliolate; petiole and rachis adaxially grooved, with appressed medifixed trichomes; petiole 1.3-2.5 cm; stipels minute; petiolules ca. 2 mm; leaflet blades opposite, obovate-oblong to obovate, 1.5-3 × 0.5-1.5 cm, both surfaces with appressed medifixed trichomes, adaxially sometimes glabrous, midvein adaxially impressed, secondary veins not visible, base broadly cuneate to rounded, apex rounded to emarginate. Racemes 2.5-5(-9) cm, laxly flowered; peduncle absent; bracts bristlelike, 1-1.5 mm. Pedicel 4-5 mm, reflexed in fruit. Calyx ca. 1.5 mm, with appressed medifixed trichomes; teeth triangular, as long as tube. Corolla red; standard broadly obovate, 4-5 mm, outside with brown trichomes; wings ca. 4 mm; keel as long as wings. Stamens 4-5 mm; anthers cordate. Ovary glabrous. Legume linear, deflexed and straight to semicircular but never falcate, 2.5-3 cm, hairy or glabrous; endocarp purplish red blotched. Seeds 5-12 per legume, cubic, ca. 1.5 mm. Fl. year-round, fr. Oct. 2n = 16.
Cultivated in SW Anhui, Guangdong, Guangxi, Guizhou, Hainan, Taiwan, and Yunnan [widely distributed in tropical Asia and Africa].
Indigofera tinctoria is widely used as the source of the dye indigo.