Common Name: Wild Indigo
Indigofera caroliniana is an erect, perennial plant with stems that become more or less woody, especially near the base; it can grow 30 - 200cm tall.
The plant is a minor source of the dye 'indigo'. It was cultivated as a dye plant by the European settlers in the Carolinas in the 18th century, but is little used at present[
Southeast N. America - North Carolina to Florida, west to Louisiana
Dry sandy pinelands and scrub along the coastal plains[
|Other Uses Rating||
|Cultivation Status||Cultivated, Wild
Indigo species generally grow best in a sunny position, preferring a well-drained but moist soil[
]. Many of the species will also succeed in drier conditions and in poor soils.
This species has a symbiotic relationship with certain soil bacteria; these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[
The leaves are a source of the dyestuff indigo[
The leaves and twigs of Indigofera species do not actually contain indigo, but rather they contain colourless precursors that must be extracted and then processed in order to produce the indigo dye[
The harvested leafy branches are placed in a tank containing water to which some lime has been added, and are weighted down with planks[
]. After some hours of fermentation, during which enzymic hydrolysis leads to the formation of indoxyl, the liquid is drained off and then stirred continuously for several hours to stimulate oxidation of the indoxyl[
]. Afterwards the solution is left to rest and the insoluble indigo settles to the bottom as a bluish sludge[
]. The water is drained and after the indigo has dried, it is cut into cubes or made into balls[
To dye textiles, indigo is reduced to a soluble form by a fermentation process under alkaline conditions. In traditional preparations of the dye, various reducing agents such as molasses are used, together with coconut-milk, bananas and the leaves of Psidium guajava[
]. The alkalinity is maintained by adding lime. After the textile has been dipped into solution it turns blue when exposed to the air[
Seed - it has a hard seedcoat and may benefit from scarification before sowing in order to speed up and improve germination. This can usually be done by pouring a small amount of nearly boiling water on the seeds (being careful not to cook them!) and then soaking them for 12 - 24 hours in warm water. By this time they should have imbibed moisture and swollen - if they have not, then carefully make a nick in the seedcoat (being careful not to damage the embryo) and soak for a further 12 hours before sowing.. Sow late winter in a warm greenhouse. The germination can be variable. Prick out the seedlings when large enough to handle and overwinter the young plants in a greenhouse for the first winter, planting out in late spring or early summer after the last expected frosts[
Cuttings of half-ripe wood, 5 - 8cm with a heel if possible, mid summer in individual pots in a frame. Good percentage[
]. Overwinter the young plants in a greenhouse for the first winter and plant out in late spring or early summer[
Root cuttings 3cm long in December. Good percentage[
Suckers. Remove them in the dormant season, preferably towards the end of winter, and plant out into their permanent positions.