Hyacinth Bean

Lablab purpureus is a fast-growing twining perennial, often grown as an annual, with large trifoliate leaves and showy spikes of purple, pink or white flowers. The flat, curved pods can be purple or green and hold two to six seeds. Seeds vary in colour from white and cream to brown, red or black, and are plump and slightly flattened with a distinct raised white hilum along one edge. The flavour is earthy and mildly sweet, a little like other field beans, with a dense, starchy texture when cooked. Immature pods are eaten as vegetables, and dry seeds are sold whole or split. Leaves, flowers and roots are also eaten in some regions, while the plant serves as forage and green manure.

The hyacinth bean is native to Africa and was domesticated there, with the greatest wild diversity found in the savannas of eastern and southern Africa. From Africa it spread to India probably several thousand years ago, and India became a second centre of diversity with many local cultivars. The species name purpureus refers to its purple flowers and stems. The unusual word lablab is thought to come from Arabic and is applied in several languages to this bean. Its common English name compares the flower spikes to those of the hyacinth. Today it is grown widely in tropical and subtropical regions, including East Africa, India, Southeast Asia, Australia and the Caribbean.

Hyacinth bean has been cultivated for millennia and is mentioned among crops in ancient Egypt in some accounts, which explains the name Egyptian bean. In India it entered cuisine early and developed into numerous regional varieties, such as the flat green pods called sem or avarekai in Karnataka, where an annual festival celebrates the fresh seeds. Its drought tolerance and ability to fix nitrogen made it valuable in mixed farming systems in Africa, where smallholders intercropped it with cereals, and it was fed to livestock. In the nineteenth and twentieth centuries it spread as a forage crop to Australia and the Americas. Gardeners in Europe and North America adopted it as an ornamental, with the purple-podded varieties admired in Thomas Jefferson's Monticello garden records. In recent decades, researchers have championed lablab as an underused crop for climate-resilient food and fodder, noting its wide genetic variation.

Fresh immature pods are cooked as a vegetable in curries, stir-fries and stews, especially in India, Bangladesh and Southeast Asia. The mature seeds are simmered into dal, soups and stews, or sprouted. In Karnataka, avarekai is made into upma, usli and fried snacks during the harvest season. In East Africa, the seeds are cooked with maize, and leaves are eaten as greens. The vine is used as animal forage, a soil-improving cover crop, and a showy trellis plant in gardens.

Mature hyacinth beans provide protein, complex carbohydrate, fibre, and minerals such as iron, folate and potassium, making them a useful pulse in plant-based diets, especially where animal protein is scarce. Some varieties contain polyphenols and other bioactive compounds that are under study. As with other legumes, the evidence for specific therapeutic effects is limited, and the main nutritional benefit is as a protein- and fibre-rich staple when properly prepared.