Indigofera arrecta aka Bengal Indigo

Indigofera arrecta is a perennial plant in the pea family, Fabaceae. Its common names include Bengal indigo, Java indigo, and Natal indigo. It comes from tropical Africa and parts of Arabia. Its African range runs from Senegal to Somalia, then south to South Africa. It grows in bushland, woodland, grassland, and along forest edges. It also grows beside roads, on flood plains, and on disturbed ground.

This bushy plant has many branches and partly woody stems. The stems spread outward or rise from the base. Useful Tropical Plants gives a usual height of 1–6.6 feet [0.3–2 metres]. PFAF lists a garden size of 6.6 feet [2 metres] tall and wide. Taller plants can reach 9.8 feet [3 metres], according to Useful Tropical Plants. PFAF mentions an upper height of 13.1 feet [4 metres]. The leaves have a light covering of hairs. Flowers are pink or brown. Plants may start to flower three months after sowing.

Bengal indigo grows best in hot, moist sites with full sun. It does not grow well in shade. It accepts sandy, loamy, and clay soils, but prefers good drainage. Moist soil suits it best, though plants can endure two months of waterlogging. Its preferred soil pH is 5–6, with tolerance from 4.5–6.5. PFAF lists USDA zones 10–12 for this tropical plant. Seeds have a hard coat that needs treatment before sowing. Nicking the coat and soaking the seed can help water enter.

This species is an important source of blue indigo dye. Its leaves and twigs hold compounds that yield dye after processing. Growers also use it as a cover crop and green manure. It fixes nitrogen and helps improve soil. In plantations, it provides shade and helps limit weeds. Growers plant it among tea, coffee, and rubber crops. They also use it for hedges along land contours. Waste left after dye extraction can return to the soil as manure.

People cook the young leaves and eat them as a vegetable. PFAF says the root may also be edible, but gives no firm confirmation. Traditional medicine uses the leaves and roots for many complaints. These include skin sores, stomach problems, and nervous disorders. The reported uses also include preparations intended to cause abortion. These records describe traditional use, not proven safety or treatment. Both sources list no known hazards, which does not establish safety.