Common Name: Winged Bean

General Information

Psophocarpus tetragonolobus is a herbaceous, perennial climbing plant producing annual stems from a tuberous rootstock. The stems are up to 4 metres long, they scramble over the ground and twine into other vegetation for support[].
An extremely useful, multipurpose plant that is cultivated as a food plant in the tropics and sub-tropics[, , ]. It has attractive flowers and so is sometimes grown as an ornamental[].

Known Hazards

None known

Botanical References

,

Range

Original habitat is obscure, probably Tropical Africa

Habitat

Not known in the wild.

Properties

Edibility Rating
Other Uses Rating
Habit	Perennial Climber
Height	2.00 m
Pollinators	Bees, Self
Self-fertile	Yes
Cultivation Status	Cultivated, Ornamental

Cultivation Details

Winged bean is a plant mainly of the humid lowland tropics, though it can also be grown al low elevations in the subtropics and up to 2,000 metres in the tropics. It is more problematic in temperate zones since most varieties will only flower when daylight hours are around 12 per day and so the plant will often not start flowering until near the end of summer[]. However, day-neutral varieties are being developed that will flower earlier in the summer in northerly and southerly latitudes[]. The plant grows best in areas where annual daytime temperatures are within the range 18 - 30°c, but can tolerate 14 - 40°c[]. The plant can survive temperatures down to about 3°c[]. It prefers a mean annual rainfall in the range 1,000 - 2,500mm, but tolerates 500 - 4,100mm[]. A dry period when the plant is flowering and when the seed is ripening is beneficial[].
Grows best in a sunny position[]. Prefers a well-drained loamy slightly acidic soil, but there are cultivars suitable for many soil types[, ]. Tolerates heavy soils[] but dislikes wet soils[]. Prefers a pH in the range 5.5 - 7, tolerating 4.3 - 8.5[]. Dislikes drought[].
Most varieties will only flower when daylight hours are around 12 per day[] but day-neutral varieties are being developed that will flower in the summer in northerly and southerly latitudes[]. Plants are also slightly more tolerant of longer days in their second and subsequent seasons of growth[].
Plants take 60 - 80 days from sowing to the first harvest of seedpods, the plants can continue to yield for a considerable period[, ].
Mature tubers can be harvested 120 - 240 days from sowing[].
Seeds take 6 - 9 months to mature[].
Yields can be very high - up to 35 tonnes of green pods per hectare can be produced; 1 - 2 tonnes of seed (if not many of the pods are harvested); plus 2.5 - 6 tonnes of tubers[]. Pod removal stimulates tuber production, but growing the plants for seed reduces tuber yield[].
There are many named varieties[, , ].
The plant is very disease resistant[].
This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[].

Edible Uses

Young seedpods - cooked for a few minutes[, , , ]. Tender, free from stringiness, and of excellent flavour[]. Insipid[]. The young pods can also be eaten raw in salads[]. They tastes like French beans (Phaseolus vulgaris)[]. The pods are harvested when about 15 - 20 cm long and 2cm wide[]. They will store for up to 21 days at 10°c with a relative humidity of 90%[]. The yields of pods average 250 - 500g per m²[].

Immature seeds are used in soups etc[].

Mature seeds are eaten cooked[, , , ]. They are very nutritious, being rich in oil (up to 17%)[], protein, vitamin E and calcium. The seed can also be roasted and eaten like peanuts or fermented and used as tempeh[]. The seeds can be white, yellow, brown, black or variously mottled; there are 5 - 21 seeds produced in a pod and they can range from 6 - 10mm long[, ].

An edible oil is obtained from the seed[]. Similar to soya oil (from Glycine spp.)[].

Root - raw or cooked like potatoes[, ]. Long and thin with a brown skin, looking somewhat like a long yam[]. A slightly sweet flavour, it contains 20% or more protein, which is about 12 times that of potatoes[, ].

Leaves and young shoots -raw or cooked[, ]. Surprisingly delicious, with an appealing texture and an excellent flavour of their own[]. Young leaves can be used in salads, whilst older leaves are best cooked and used like spinach[, , , ]. The leaves should only be harvested up to the stage where the plant starts to flower[].

Flowers and flower buds - raw or cooked[]. A sweet flavour, they make a nice addition to salads[]. They can also be added towards the end of cooking to soups, stews, curries etc[]. They have a flavour similar to mushrooms when sautéed[]. The light blue flowers are also used as a colouring in foods[].

The roasted seed is a coffee substitute[].

Medicinal

None known

Agroforestry Uses:

A very good green manure with exceptional nitrogen-fixing properties, producing a greater weight of nodules per plant than any other member of the Fabaceae[, ]. It is used for soil improvement and restoration[].

Other Uses

None known

Propagation

Pre-soak the seed for 12 hours in warm water and sow in early spring in a warm greenhouse. Place two or three seeds in each pot, thinning to the strongest plant. Plant them out in late spring or early summer, after the last expected frosts and give them the protection of a cloche or cold frame until they are growing away strongly[].