Indigofera
Indigofera tinctoria
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Rosids
Order:	Fabales
Family:	Fabaceae
Subfamily:	Faboideae
Tribe:	Indigofereae
Genus:	Indigofera L. (1753)
Type species
Indigofera tinctoria L.
Species
See text.
Synonyms[1][2]
Acanthonotus Benth. (1849) Amecarpus Benth. (1847) Bremontiera DC. (1825) Brissonia Neck. (1790), opus utique oppr. Eleimanthus Hochst. (1846) Elasmocarpus Hochst. ex Chiov. (1903 publ. 1902) Hemispadon Endl. (1832) Indigo Adans. (1763) Oustropis G.Don (1832) Sphaeridiophorum Desv. (1813) Tricoilendus Raf. (1837) Vaughania S.Moore (1920)

Indigofera is a large genus of over 750 species^[3] of flowering plants belonging to the pea family Fabaceae. They are widely distributed throughout the tropical and subtropical regions of the world.^[3][2]

Indigofera is a varied genus that has shown unique characteristics making it an interesting candidate as a potential perennial crop.^{[clarification needed]} Specifically, there is diverse variation among species with a number of unique characteristics. Some examples of this diversity include differences in pericarp thickness, fruit type, and flowering morphology. The unique characteristics it has displayed include potential for mixed smallholder systems with at least one other species and a resilience that allows for constant nitrogen uptake despite varying conditions.

Species of Indigofera are mostly shrubs, though some are small trees or herbaceous perennials or annuals. The branches are covered with silky hairs. Most of them have pinnate leaves made of three foliolates with short petioles.^{[3][4]: 341}

Small flowers grow in the leaf axils from long peduncles or spikes, their petals come in hues of red or purple, but there are a few greenish-white and yellow-flowered species.^[4]: 341 Indigofera flowers have open carpels, their organ primordial^{[clarification needed]} is often formed at deeper layers than other eudicots.^[5] This variety could have significant implications on its role in an actual perennial polyculture. For example, different flowering morphologies could be artificially selected for in varying directions in order to better fit in different environmental conditions and with different populations of other plants.

The fruit is a long, cylindrical legume pod of varying size and shape.^{[3][4]: 341}

The types of fruit produced by different species of Indigofera can also be divided into broad categories that again show great variation. The three basic types of fruit categories can be separated by their curvature including straight, slightly curved, and falcate (sickle-shaped). In addition, several of the species including Indigofera microcarpa, Indigofera suffruticosa, and Indigofera enneaphylla have shown delayed dehiscence (maturing) of fruits^[6] This variation could again allow for artificial selection of the most abundant and nutritious fruit types and shapes.

Another way to categorize Indigofera is by its pericarp thickness. The pericarp (the tissue from the ovary that surrounds the seeds) can be categorized as type I, type II, and type III with type I having the thinnest pericarp and fewest layers of schlerenchymatous (stiff) tissue and type III having the thickest pericarp and most schlerenchymatous layers. Despite the previous examples of delayed dehiscence, most fruits of this genus show normal explosive dehiscence to disperse seeds.^[7] Similar to fruit shape, the variation in fruit sizes allows for the thickest and most bountiful fruits to be selected.

Several species, especially Indigofera tinctoria and Indigofera suffruticosa, are used to produce the dye indigo. Scraps of Indigo-dyed fabric likely dyed with plants from the genus Indigofera discovered at Huaca Prieta predate Egyptian indigo-dyed fabrics by more than 1,500 years.^[8] Colonial planters in the Caribbean grew indigo and transplanted its cultivation when they settled in the colony of South Carolina and North Carolina where people of the Tuscarora confederacy adopted the dyeing process for head wraps and clothing. Exports of the crop did not expand until the mid-to late 18th century. When Eliza Lucas Pinckney and enslaved Africans successfully cultivated new strains near Charleston it became the second most important cash crop in the colony (after rice) before the American Revolution. It comprised more than one-third of all exports in value.

The chemical aniline, from which many important dyes are derived, was first synthesized from Indigofera suffruticosa (syn. Indigofera anil, whence the name aniline).

In Indonesia, the Sundanese use Indigofera tinctoria (known locally as tarum or nila) as dye for batik. Marco Polo was the first to report on the preparation of indigo in India. Indigo was quite often used in European easel painting^{[clarification needed]} during the Middle Ages.^[9][10]

Indigofera comprises the following species:^{[11][3][12][13][14]}

The status of the following species is unresolved:^[13][14]

Indigofera species are used as food plants by the larvae of some Lepidoptera species, including the turnip moth (Agrotis segetum).

• Baptisia (false indigo)—a related genus.

• Kumar P. (2012). Indigo Plantations and Science in Colonial India. Cambridge University Press. p. 350. ISBN 978-1-107-02325-3.

• Indigofera. eFloras Lists.
• Dressler, S.; Schmidt, M. & Zizka, G. (2014). "Indigofera". African plants – a Photo Guide. Frankfurt/Main: Forschungsinstitut Senckenberg.