Common Name: Anil Indigo

General Information

Indigofera suffruticosa is a sparsely branched, stiffly erect, perennial plant growing from 45 - 250cm tall[]. It has a woody rootstock from which grow stems that are often woody and persist for more than a year but can also be herbaceous[].
Indigo, of which this species is a major 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[]. Indigo is and has been obtained from various species of Indigofera, but this is the species most exploited in Central America[]. Before the introduction of coffee, indigo was one of the most important exports of Central America, but it is now grown commercially only in northern Salvador[]. Indigo dye and the indigo used for whitening clothing when being laundered is now made synthetically, like so many other dyes formerly obtained as natural plant products[].

Known Hazards

An aqueous extract of the fruit has an hepatotoxic effect and causes chromosome aberrations[].

Botanical References

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Range

S. America - Argentina, Paraguay, north to the Caribbean, through Central America to Mexico, Florida

Habitat

Dry to wet fields and thickets, often in waste ground, sometimes on exposed hillsides or on sandbars, sometimes a weed in cultivated ground, most commonly at low elevations, but extending to 1,500 metres[].

Properties

Weed Potential	Yes
Medicinal Rating
Other Uses Rating
Habit	Perennial
Height	1.50 m
Cultivation Status	Cultivated

Cultivation Details

Indigofera suffruticosa succeeds in tropical and subtropical climates, growing best where the mean annual temperature is wirthin the range 15 - 27°c. Plants are not frost resistant according to one report[], whilst another says that occasional light frosts are tolerated[]. Prefers a mean annual rainfall in the range 700 - 4,000mm[]..
Grows best in a sunny position, succeeding in a range of soil conditions so long as they are well-drained[]. Well adapted to fertile silty-sandy soils[]. Succeeds in soils with low fertility[]. Grows well in soils with a low pH[]. Established plants are drought resistant[].
Indigofera suffruticosa is native to the Americas but has been widely introduced elsewhere as a source of dye and for medicinal purposes and has commonly become naturalized. It tolerates a range of soil types and may become dominant in disturbed habitats. It is now classed as invasive on many Pacific Islands including Hawaii, Samoa, Tonga, the Cook Islands and Fiji. It is not often a weed of crops but tends to replace native vegetation. In Hawaii it threatens the endangered species Panicum fauriei var. carteri, Spermolepis hawaiiensis and Wilkesia hobdyi[].
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 plant finds some use in domestic medicine in Guatemala. Indigo is often applied to the stings of bees and other insects to reduce pain and inflammation, although its efficacy is somewhat doubtful[].

A decoction of the roots is taken against stomach-ache[].

A tincture of the roots and seeds in rum is used as a vermifuge[].

The dried and powdered seeds are used in the treatment of ulcers[].

The leaves are resolutive and sudorific[]. An infusion of bruised leaves is used as a treatment for fever[]. Combined with the leaves of Indigofera tinctoria and the bark of Phellodendron chinense, it is used as a medicine against scrofula[].
The fresh leaves are used in a warm bath to act as a calmative[].

The plant juice is used as a treatment for diarrhoea[].

Agroforestry Uses:

Grown as a cover crop and green manure in coffee, rubber and tea plantations[]. In South America it is one of the components of natural pastures developing after clearing rain forest[]. A good cover of the plant can increase the nitrogen content of the soil considerably. In Sri Lanka for example, an increase from 3.7% to 5.3% in 4 years was found[].

Other Uses

The plant is a major source of the blue dye indigo[]. Plants contain the glucoside indican, which transforms into indoxyl (indigo-white) and glucose by enzymatic hydrolysis[]. Indoxyl can then be oxidized to the dye indigo-blue[].
It is perhaps just as well for Central America that the cultivation of indigo has largely been abandoned, since preparation of the dye was injurious to the health of persons employed in the industry. The freshly cut plants were immersed in large vats lined with bricks, such as may sometimes be discovered even now about Central American fincas. After fermentation had proceeded for some time, the plants were trampled by men in the tanks, after which the dye settled to the bottom of the water and was formed into small cakes that were later dried[]. Indigo was formerly much planted in some parts of Guatemala, especially in the Oriente and along the Pacific foothills and plains, and some is grown even today, for dyeing native textiles. The indigo-coloured coats and trousers forming the costumes of the men of certain highland towns are most distinctive. As late as 1883 it was reported that 135 quintales (hundredweight) of indigo were exported from Guatemala.

An extract of the leaves and stems is used as an ingredient in commercial cosmetic preparations as a skin conditioner[].

The powdered seeds and roots are used as an insecticide[].

Propagation

Seed - sowing is done either in seed-beds or directly into the field[]. Pre-soak the seed in warm water overnight for optimal germination[]. Germination takes 4 - 6 days[]. Seedlings quickly develop a deep root system and so, when a seed-bed is used the seedlings should be transplanted into their permanent positions within 4 - 6 weeks after sowing[].
Stem cuttings are taken from well developed branches divided into 30 cm long pieces[]. They are kept for 2 - 3 days in a cool place before planting out, 2 - 3 per hole. Rooting starts in the second week[].

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