The Winged bean (Psophocarpus tetragonolobus), also known as the Goa bean, is a tropical legume plant native to Papua New Guinea. It grows abundantly in hot, humid equatorial countries, from the Philippines and Indonesia to India, Burma and Sri Lanka. It does well in humid tropics with high rainfall.
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 dark red. The beans themselves are similar to soybeans in both use and nutritional content (being 29.8% to 39% protein).
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.
