Indigofera hendecaphylla and Indigofera spicata Forssk., used to be considered as the same species and were then united under Indigofera spicata. They are now considered to be different species. The literature is therefore confusing, and references to toxicity most probably refer to Indigofera hendecaphylla[
Indigofera compressa auct.
Indigofera endecaphylla auct.
Indigofera enneaphylla auct.
Indigofera hendecaphylla auct.
Indigofera neglecta N.E.Br.
Indigofera parkeri Baker
Indigofera parvula Robyns
Indigofera pusilla Lam.
Common Name: Creeping Indigo
Indigofera spicata is a prostrate, herbaceous perennial plant with several stems radiating from a central woody, strongly taprooted, rootstock[
]. The stems can attain a length of 2 - 3 metres, and may produce roots from the nodes. Plants grow taller as they mature, and after two years are normally 30 - 40cm tall[
The plant is harvested from the wild for local use as a medicine and source of materials. Indigo, of which this species is a minor 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. This species was at one time cultivated for this purpose but, with the advent of synthetic dyes, demand for the plant dropped dramatically[
]. The plants adaptability to various soil types and usefulness in erosion control, crop cover and green manures has led to its widespread cultivation and use across tropical regions around the world[
Reports of toxicity for this species are often confused with the closely related Indigofera hendecaphylla. It is likely that Indigofera hendecaphylla is the more toxic of the two, but this is not clear. Below are the reports on toxicity for the two species.
Some strains of this species have leaves and seeds that are highly hepatotoxic[
The leaves of Indigofera hendecaphylla, possibly only of tetraploid forms originally from Sri Lanka, contain per 100 g dry matter 0.1 - 0.5 g indospicine (2,7-diamino-7-amino-heptanoic acid) while the seeds contain 0.1 - 2 g. Indospicine is a specific antagonist of arginine, interfering with its synthesis and incorporation into proteins and with the synthesis of DNA. Indospicine is highly toxic to chicken, rabbits, pigs, goats, sheep, cattle and horses. In small doses it causes loss of vitality and abortion in cattle and goats. Indospicine is especially dangerous to horses, which relish plants containing it and eat them preferentially[
Tropical Africa - widespread, avoiding areas of higher rainfall, from Cameroon to Ehiopia, south to S. Africa, Madagascar; Arabian Peninsula - Yemen
Disturbed grasslands, cultivated areas and waste places; at elevations up to 2,700 metres[
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Indigofera spicata is widespread in the tropical regions of Africa, where it tends to avoid areas of higher rainfall; it can be found at elevations up to 2,700 metres. It grows best in areas where annual daytime temperatures are within the range 22 - 30°c, but can tolerate 13 - 36°c[
]. It is not tolerant of frost[
]. It prefers a mean annual rainfall in the range 1,500 - 2,000mm, but tolerates 500 - 4,300mm[
Prefers a sunny position but tolerates light shade. The plant is well adapted to a wide range of soil types - it thrives best on clay soils, but can tolerate various soil types including limestone, sandy, nutrient-poor and phosphorus-deficient, as well as moderately acidic[
]. It prefers a pH in the range 5 - 6.5, tolerating 4.5 - 7.7[
Indigofera spicata may potentially threaten native flora, as it will send out trailing stems reaching up to 3 metres long, producing numerous adventitious roots at the nodes and smothering other weeds[
].The plant is invasive to many parts of Asia and the Pacific, including French Polynesia (Marquesas Islands, Society Islands., Austral Islands), the Cook Islands (Mangaia), Micronesia (Pohnpei and Nauru), New Caledonia, Hawaii, Singapore, Japan, and Taiwan. Other tropical places where it is a known weed include Australia, Puerto Rico and adjacent islands, the United States (southern Florida), French West Indies (Guadeloupe), and Mexico[
The plant will usually maintain itself by self-sowing[
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 root is abortifacient, ecbolic, vermifuge. It is also used in the treatment of naso-pharyngeal affections, tonsilitis, pulmonary troubles, stomach troubles[
The whole plant is used to treat diarrhoea, ascariasis and stomach aches[
With its fast growth, creeping habit and ability to fix atmospheric nitrogen, this plant has often been used as a green manure and soil stabilizer. It is cultivated in coffee, tea and rubber plantations[
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[
The roots are used as chew-sticks to clean the teeth and maintain oral hygiene[
Like many species within the family Fabaceae, once they have been dried for storage the seeds of this species 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[
Cuttings of about 20cm long are planted in situ at a spacing of 60 cm x 60 cm with 5 cuttings per hole. Plants produced from cuttings usually remain very low and cover rarely exceeds 12cm in height. A fair cover can be established in 4 - 6 months and a continuous, even cover in a year from planting[