The winged bean, also known as the Goa bean, Psophocarpus tetragonolobus, is a tropical plant found chiefly in rural areas of Papua (New Guinea) and Southeast Asia. It grows abundantly in hot, humid equatorial countries, from the Philippines and Indonesia to India, Burma and Sri Lanka.

The winged bean plant grows as a vine with climbing stems and leaves, 3-4 m in height. It is an herbaceous perennial, but can be grown as an annual. It is generally taller and more massive than the Common bean. The bean pod is typically 15-22 cm (6-9 in) long and has four wings with frilly edges running lengthwise. The skin is waxy and the flesh partially translucent in the young pods. When the pod is fully ripe, it turns an ash-brown color and splits open to release the seeds. The large flower is a beautiful pale blue.

The plant is one of the best nitrogen fixers with nodulation accomplished by the soil bacterium Rhizobium. Because of its ability to fix nitrogen from the atmosphere, the plant requires very little or no fertilizers.

Being a tropical plant, it is sensitive to frost. It will not flower if day length is more than 12 hours. The seeds have a hard coat and it helps to presoak the seeds before planting to hasten germination. The plant grows very quickly, reaching a length of four meters in a few weeks.

Uses

This bean has been called the “one species supermarket” because practically all of the plant is edible. The beans are used as a vegetable, but the other parts (leaves, flowers, and tuberous roots) are also edible. The flowers are often used to color rice and pastries. The flavor of the beans has a similarity to asparagus. The young leaves can be picked and prepared as a leaf vegetable, similar to spinach. The roots can be used as a root vegetable, similar to the potato, and have a nutty flavor; they are also much more rich in protein than potatoes. The dried seeds can be useful as a flour and also to make a coffee-like drink. Each of these parts of the winged bean provide a source of vitamin A and other vitamins.

It is possible that, with a little genetic improvement through selective breeding, the winged bean could raise the standard of living for millions of people in poor, tropical countries.

References

• Venketeswaran, S., M.A.D.L. Dias, and U.V. Weyers. The winged bean: A potential protein crop. p. 445. In: J. Janick and J.E. Simon (eds.), Advances in new crops. Timber Press, Portland, OR (1990).
• Entry for the Winged Bean in the “Leaf for Life” website
• Wilson, Edward O.; The Diversity of Life. The Belknap Press of Harvard University Press, Cambridge, Massachusetts (1992).