Common Name:

General Information

Indigofera hirsuta is an erect or spreading herbaceous legume growing 60 - 230cm tall, with spreading or ascending branches[]. More or less annual in habit, the stems can become somewhat woody and persist for more than a year[].
The plant is harvested from the wild for local use as a medicine and a dye (a minor source of indigo). It is often grown as a ground cover and green manure[].

Known Hazards

The plant is possibly poisonous and can severely irritate the hooves of animals[].

Botanical References

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Range

Tropical Africa - Senegal to Sudan, south to Angola, Mozambique and Madagascar; through tropical Asia to northern Australia.

Habitat

A weed in cultivated and waste areas, in grassland, savannah, dry and deciduous forest, on river banks and beaches, at elevations from sea level to 1,500 metres[].

Properties

Weed Potential	Yes
Medicinal Rating
Other Uses Rating
Habit	Annual
Height	1.20 m
Pollinators	Insects
Cultivation Status	Cultivated, Wild

Cultivation Details

A plant of the moist tropics, where it is found at elevations up to 1,350 metres. It grows best in areas where annual daytime temperatures are within the range 22 - 30°c, but can tolerate 13 - 34°c[]. It is intolerant of frost[]. It prefers a mean annual rainfall in the range 900 - 1,700mm, but tolerates 750 - 2,700mm[].
Succeeds in full sun and in light shade[]. Grows best in a well-drained, moderately fertile, light to medium textured soil[]. Tolerant of poor soils, it grows well on moderately poor, sandy soils with a low pH[]. Prefers a pH in the range 5.5 - 6.5, tolerating 4.5 - 8[].
Indigofera hirsuta has been widely introduced as a cover crop and forage plant in the tropics, and is now naturalized in many parts of the world including the Americas. It may compete with and dominate the native flora, as it is well adapted to a wide range of soil types. As a free-seeding annual without specific Rhizobium requirements, it can quickly spread and naturalize in suitable habitats, especially arable and disturbed land. It has been declared a weed in many countries - in Florida, the species has proven to be self-regenerating, even in fields that have been burned or disked[, , ].
A summer annual or biennial plant, flowering in the summer and fruiting in early autumn. If cut in late summer, a second growth may be expected[]. Total life span for dye crops is 2 - 3 years and 1.5 - 2 years for cover crops[].
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[].

Edible Uses

None known

Medicinal

The leaves are considered to be laxative, generally healing and pain relieving. They are used in the treatment of a range of conditions including liver problems, pulmonary problems, yaws, paralysis, epilepsy, convulsions, spasms and insanity[]. A decoction made from the leaves is used as a treatment against stomach problems and yaws[].

The whole plant/seed is ophthalmic[].

The root is diuretic. It is used to treat kidney problems, haemorrhoids, venereal diseases and food poisoning[].

Agroforestry Uses:

The plant is grown as a cover crop and for soil improvement. It is mixed with grass grown for pasture[]. It is a valuable green manure and cover crop, used especially in tea, coffee and rubber plantations[]. It is used especially where erosion control is important[].

Other Uses

The leaves are a source of the dye 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[].

An insecticide and an arachnicide can be made from the root and seed[].

Propagation

Seed - sow in situ[]. The seed has a hard seedcoat and may benefit from scarification before sowing to speed up 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[]. Germination of treated seed takes 7 - 9 days[]. Early growth of the seedlings is very slow, it can be 6 weeks or more before they are large enough to be able to weed them[].

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