Indigofera tinctoria L.
(Fabaceae – the pea family)
subfamily: Faboideae – the bean subfamily
common names: Indigo, True Indigo
Indigofera is from the Spanish indigo, through the Latin indicum, indigo, and fero, to bear, carry. It is a genus of about 700 species of flowering plants occurring throughout the tropical and subtropical regions of the world, with a few species reaching the temperate zone in eastern Asia. They are mostly shrubs, though some are herbaceous, and a few can become small trees reaching up to 5 or 6 m tall. Most are dry-season or winter deciduous. The leaves are pinnate with 5–31 leaflets, including a terminal leaflet. Leaf lengths vary from 3 cm to 25 cm. The flowers are small, produced on racemes 2–15 cm long.
Tinctoria is derived from the Latin tinctus, dyed. Indigofera tinctoria is a deciduous shrub growing 1–2 m high, and is insect pollinated. As it has been widely cultivated and naturalized throughout the tropics, the exact native distribution has been obscured; but it is thought to have been from the eastern Asia – China region. The flowers are pink, and the pods are typically scimitar-shaped.
India is one of the oldest-known centres of indigo dye production. The association of India with indigo is revealed in the Greek word for the dye, ινδικον (indikon), which is merely the adjective ‘Indian’. The Latin word for the plant was derived from this. Many species of the Indigofera genus give blue indigo dye, but Indigofera tinctoria is usually the type preferred for cultivation, as it gives the highest yield.
The Romans used indigo as a pigment for painting, and also for medicinal and cosmetic purposes. It was a luxury, being imported from India to the Mediterranean by Arab merchants. In 1498 the Portuguese Vasco da Gama discovered a sea route to India. This enabled direct trade with India and the far east, bypassing the tax sites on the old land route where heavy taxes were levied on the passage of indigo and other luxury items. There was now a significant rise in the amount of tropical indigo arriving in Europe. This had a serious effect on the European production of blue dyes, mainly from woad. The woad plant is Isatis tinctoria, native to the steppes and deserts of the Caucasus and central Asia, but spread to and naturalized in many parts of Europe, where it was extensively cultivated for the production of its dye, also known as woad. This industry was threatened by the appearance of a better supply of indigo, and many governments, particularly those of Great Britain, France and Germany, outlawed the importation of tropical indigo. Eventually the European powers established their own indigo plantations in the new American and Caribbean colonies, and the importation of indigo from these plantations eventually led to the demise of the woad industry.
In response to environmental concerns, more interest is now being shown in the revival of the indigo dye industry in developing countries, where, not only can dye be produced with less atmospheric pollution than the chemical dye industry generates, but village-based Indigofera growing and dye production provides a new source of income, particularly for the women, and assists to rejuvenate degraded land by the nitrogen-fixing properties of the legume.
Photographs © Donald Simpson, taken in Picnic Bay 2009, 2010