Dye indigo

Indigofera tinctoria (true indigo, dye indigo) is a shrub or subshrub in the legume family (Fabaceae), typically 1–2 m tall, probably native to tropical Asia and now cultivated and naturalised throughout the tropics. It has slender, much-branched stems bearing pinnately compound leaves with several pairs of small, oval, grey-green leaflets that are appressed-hairy beneath. The small pinkish to coppery-red pea-like flowers are arranged in short axillary racemes, followed by narrow, curved cylindrical pods containing several seeds. The plant is best known historically as the principal source of natural indigo dye, the blue pigment being produced by fermentation of the leaves, which yield the precursor indican. Long valued as a commercial dye crop, it grows readily in warm, well-drained soils and has been spread worldwide through cultivation.