Common name: True indigo, Neelayamari, Amari
A small, well-branched shrub belong to the pea family, True indigo plants were traditionally used to produce indigo or blue dye. Now with synthetic dyes gaining popularity, True indigo plants are not in demand anymore. They are now seen in the wild, in empty plots, roadsides, hillsides and open areas.
These plants can grow to a height of 1-2 meters with well-branched, woody stems and small, green, pinnate leaves. The leaves are 8-10 cms long with 9-13 small, oppositely-placed leaflets.
The plants flower copiously, producing blue or violet flowers very similar to those of peas or beans. The flowers are borne on long racemes that are 3-5 cms long. These flowers then turn into green and then brown pods that are 3-4 cms long. Each seedpod contains 5-10 small seeds that are about 1.5mm in diameter.
The intensity and fastness of color obtained from this plant made it a favorite in olden times and was called the ‘king of dyes’. There are records of the True indigo plants being used over 4000 years ago in dyeing the garments of Egyptian royalty.
These plants are now naturalized in warm tropical weather in Asia and Africa, though the country of origin is unknown. They need bright sunlight and well-drained soil, but is not fussy about the nutrients in the soil.
In fact, being a leguminous plant, True Indigo plant roots contain nitrogen-fixing bacteria that can absorb atmospheric nitrogen and convert it into a form of nitrogen that can be absorbed by plants. For this reason, these plants are grown as ground cover and alternate crops that improve soil quality.
The dye is obtained from the leaves of the plant, which are harvested by cutting the stems when the plants are 4-5 months old. The harvested branches are placed in large tanks containing water mixed with lime. The fermentation process creates a chemical called Indoxyl which on oxidation produces indigo dye.
This insoluble dye settles at the bottom of the tank, which is dried and cut into cubes or made into balls. Indigo dye has to go through further chemical processes before it can be used on fabrics.
True indigo plants have medicinal uses as well, the leaves are used in treatment of wounds, ulcers, sores, hemorrhoids, and skin diseases. An infusion of the leaves can treat nerve disorders, epilepsy, asthma, bronchitis, liver and kidney ailments, fever and spleen infections.
Roots are used to treat worm infections, toothache, gonorrhea, kidney stones, insect and scorpion stings. Twigs of True indigo plant are used as toothbrushes after crushing it lightly to bring out the fibers. Leaves are also used in cosmetic preparations such as skin conditioners and masking agents.
Propagation is through seeds and stem cuttings.
Indigofera tinctoria: True indigo