This species has been much confused with Indigofera articulata Gouan.[
Indigofera coerulea is a stout shrubby semi-woody herb or shrub that can grow up to 2 metres tall[
Indigo, of which this species is a secondary source, has a very long history of use as a dye. Because of its fascinating deep blue colour, its great colour fastness to light and the wide range of colours obtained by combining it with other natural dyes, it has been called 'the king of dyes' and no other dye plants have had such a prominent place in as many civilizations as this genus. It was at one time widely cultivated for this purpose but, with the advent of synthetic dyes, demand for the plant dropped dramatically[
]. It is still sometimes grown for indigo in drier areas[
Africa - Egypt, Niger, Chad, Sudan, Eritrea, Ethiopia, Uganda, Djibuti, Somalia, Kenya; through the Arabian Peninsula to Pakistan, India, Sri Lanka.
Subdesert and open Acacia - Commiphora bushland; sandy-clayey hollows, humid or flooded; dry grassland; roadsides; coastal arid plains; at elevations from 200 - 2,700 metres[
|Other Uses Rating||
|Cultivation Status||Cultivated, Wild
A plant of arid and semi-arid tropical and subtropical areas, where it is found at elevations from 200 - 2,700 metres. It can be found in areas where the mean annual rainfall is as low as 200 - 250mm[
The dried, ground up leaves and roots are used as a wound dressing[
An extract of the leaves is drunk as a remedy for constipation and is applied as a wash against infected eyes[
All the above-ground parts of the plant are a source of the dye indigo, which is used to colour textiles blue. The leaves and twigs do not actually contain indigo but 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.
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