Psophocarpus scandens (PROTA)

Plant Resources of Tropical Africa Introduction

List of species

General importance
Geographic coverage Africa
Geographic coverage World
Medicinal
Forage / feed

Psophocarpus scandens (Endl.) Verdc.

Protologue: Taxon 17: 539 (1968).

Family: Papilionaceae (Leguminosae - Papilionoideae, Fabaceae)

Chromosome number: 2n = 18

Synonyms

Psophocarpus longepedunculatus Hassk. (1842), Psophocarpus palustris auct. non Desv.

Vernacular names

African winged bean, tropical African winged bean, kikalakasa (En). Pois ailé africain, kikalakasa (Fr). Mabala (Po).

Origin and geographic distribution

African winged bean is a common wild plant in Central and East Africa and the Indian Ocean islands, extending to eastern West Africa (Nigeria) and the northern part of southern Africa (Malawi, Zambia, Angola, Mozambique). It has been introduced in Jamaica and Brazil, where it is naturalized. A recent promotion campaign in DR Congo made it a quite popular vegetable for home gardens and a commercial crop for local markets, especially around Kinshasa. It was introduced as a cultivated leafy vegetable in several African countries, but acceptance was minimal, although the trials have been successful from the production point of view.

Uses

The main product of African winged bean are the leaves and young sprouts, consumed as potherb. The immature fruits and ripe seeds are also eaten. In DR Congo African winged bean leaves are recommended as a galactagogue for women who are breastfeeding. The leaves made into a poultice are applied in the treatment of lumbago, wounds and haemorrhoids. A tea from the leaves is taken to relieve stomach-ache. Psophocarpus scandens is grown as a cover crop in Africa and Asia, e.g. in oil palm or rubber plantations, whereas the leaves mixed with other legumes and grasses are used as fodder.

Production and international trade

African winged bean is mainly collected from the wild, but it is grown in home gardens and in DR Congo also for local markets. No international trade is known to exist.

Properties

In DR Congo young fresh leaves were found to contain per 100 g edible portion: water 82 g, protein 7.1 g, fat 2.2 g, carbohydrate 5.8 g, Ca 565 mg, P 65 mg, Mg 270 mg. The nutritional composition of young fruits per 100 g is: water 87 g, protein 3.6 g, fat 0.35 g, carbohydrate 7.3 g, Ca 297 mg, P 61 mg, Mg 200 mg (Harder, D., Lolema, O.P.M. & Tshisand, M., 1990).

Adulterations and substitutes

The taste of eru (Gnetum spp.) is rather similar to the cheaper and more widely available African winged bean leaves.

Description

Perennial climbing or twining herb; stem up to 6 m long, glabrous or sparsely pubescent. Leaves alternate, 3-foliolate; stipules oblong-lanceolate, 1–1.5 cm long, spurred, persistent; petiole 5–18 cm long, rachis 1–5 cm long; leaflets ovate-rhomboid to broadly rounded, 2.5–12 cm × 2–10 cm, cuneate to truncate at base, acute or acuminate at apex, occasionally 3-lobed, glabrous or glabrescent on both surfaces, margin often ciliate. Inflorescence a few- to many-flowered pseudoraceme; peduncle 3–40 cm long, rachis 5–12 cm long, pubescent; bracts semi-caducous, up to 1 cm long, bracteoles persistent, up to 1.5 cm long. Flowers bisexual, papilionaceous; pedicel 2–6 mm long, pubescent; calyx with tube 5–7 mm long, lobes unequal, up to 3.5 mm long; corolla with obovate-oblong standard up to 2 cm × 1.5 cm, pale blue or mauve, emarginate, blue-lilac wings and blue-lilac or whitish keel; stamens 10, 9 with fused filaments and 1 free or somewhat connate in the middle; ovary superior, oblong, 1-celled, style bent, with a row of hairs below the stigma. Fruit an oblong pod, square in cross-section, 3.5–8 cm × 6–7 mm, prominently 4-winged, glabrous, 4–8-seeded. Seeds oblong to cylindrical, (5–)6–7.5 mm × (3.5–)5–6 mm, blackish-purple, with minute granular, orange, easily removable tomentum or brown silky hairs on the edges. Seedling with epigeal germination.

Other botanical information

Psophocarpus comprises about 10 species, one of which is only known from cultivation: winged bean, Psophocarpus tetragonolobus (L.) DC. The other species are all native to tropical Africa.

Psophocarpus scandens is closely related to Psophocarpus palustris Desv., which occurs from Senegal to Sudan. The latter species is also known as African winged bean and is still often confounded with Psophocarpus scandens. Psophocarpus palustris differs from Psophocarpus scandens in its leaflets which are usually more hairy beneath, its shorter bracteoles (up to 6.5 mm long) and usually shorter fruits (2.5–5.5 cm). In the region where the distribution areas of the two species meet (Nigeria to Sudan) some intermediate specimens, perhaps hybrids, have been found. Most agronomic information published under Psophocarpus palustris should be attributed to Psophocarpus scandens. However, Psophocarpus palustris is undoubtedly similarly used as a vegetable; the young fruits are eaten in Senegal.

Leaves and young pods of Psophocarpus grandiflorus R.Wilczek are eaten in DR Congo after boiling in water or milk. Roasted seeds are also eaten. Wooden statuary and artefacts are rubbed with the leaves to darken them. The strong shoots serve for tying purposes. A leaf infusion is given to induce labour in humans and cattle. Psophocarpus grandiflorus has larger flowers than Psophocarpus scandens and is restricted to high-altitude areas in eastern DR Congo, Ethiopia and Uganda.

Ecology

In the wild, Psophocarpus scandens occurs in lowland areas up to 1000 m altitude, in DR Congo in regions with an annual rainfall of 1200–1800 mm and a mean annual temperature of 25°C. It prefers swampy localities, periodically flooded forest and river banks, but occurs also in drier localities, e.g. in grassland, thickets and fallow land.

Propagation and planting

The seeds are very hard and can be kept for several years. They require scarification before planting. The weight of 100 seeds is 9–10 g. The spacing depends on the method of growing. When grown on flat land a distance of 50 cm × 50 cm is adequate; when allowed to climb fences, trellises or shrubs in the garden, one or two seeds are placed near the base of the support.

Management

Early weeding is required as initial growth is slow. In DR Congo, people plant African winged bean on open land, often in association with sweet potatoes. It is also planted as a cover crop in agricultural systems with banana, maize, cassava, oil palm and rubber.

Diseases and pests

Psophocarpus scandens is generally little affected by diseases and pests. It is resistant to several diseases and pests affecting Psophocarpus tetragonolobus such as false rust (Synchytrium psophocarpi) and dark leaf spot (Pseudocercospora psophocarpi). It is also less susceptible to necrotic mosaic virus and flower blight. The nematode Heterodera marioni attacks it in Mauritius and Sumatra (Indonesia). In DR Congo bruchid weevils attack the seed.

Harvesting

The leaves are mainly picked before the plants set fruit.

Handling after harvest

The leaves can be dried and powdered for long-term conservation. The seeds can be roasted and give good flour.

Genetic resources

African winged bean is a common wild plant, which is not in danger of genetic erosion. The International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria and the Southern Regional Plant Introduction Station, Griffin, Georgia, United States hold collections of Psophocarpus germplasm including a few accessions of Psophocarpus scandens.

Breeding

Efforts to cross Psophocarpus scandens with Psophocarpus tetragonolobus, which has the same chromosome number, have failed, probably because of differences in karyotype. If interspecific hybrids can be obtained, they will probably be sterile, so it will not be easy to transfer genes for disease and pest resistance from Psophocarpus scandens to Psophocarpus tetragonolobus.

Prospects

African winged bean is a nutritious and easy to grow vegetable. There is a need for breeding of improved cultivars, together with research on cultural practices.

Major references

• Harder, D.K., Lolema, O.P.M. & Tshisand, M., 1990. Uses, nutritional composition, and ecogeography of four species of Psophocarpus (Fabaceae, Phaseoleae) in Zaire. Economic Botany 44(3): 391–409.

• Latham, P., 2004. Useful plants of Bas-Congo province, Democratic Republic of the Congo. DFID, London, United Kingdom. 320 pp.

• Maxted, N., 1990. A phenetic investigation of Psophocarpus Neck. ex DC. (Leguminosae, Phaseoleae). Botanical Journal of the Linnean Society 102(2): 103–122.

• Maxted, N., 1991. Intergeneric relationships between Psophocarpus Necker ex DC. (Phaseoleae, Leguminosae) and its allies. Candollea 46(2): 367–382.

• Paulus, J., 1997. Extension of African winged bean in Zaire. In: Schippers, R.R. & Budd, L. (Editors). Proceedings of a workshop on African indigenous vegetables, Limbe, Cameroon, 13–18 January 1997. Natural Resources Institute/IPGRI, Chatham, United Kingdom. pp. 42–45.

• Pickersgill, B., 1980. Cytology of two species of winged bean, Psophocarpus tetragonolobus (L.) DC. and P. scandens (Endl.) Verdc. (Leguminosae). Botanical Journal of the Linnean Society 80: 279–291.

• Schippers, R.R., 2002. African indigenous vegetables, an overview of the cultivated species 2002. Revised edition on CD-ROM. National Resources International Limited, Aylesford, United Kingdom.

• Verdcourt, B. & Halliday, P., 1978. A revision of Psophocarpus (Leguminosae - Papilionoideae - Phaseolae). Kew Bulletin 33(2): 191–227.

• Wulijarni-Soetjipto, N., 1997. Psophocarpus scandens (Endl.) Verdc. In: Faridah Hanum, I. & van der Maesen, L.J.G. (Editors). Plant Resources of South-East Asia No 11. Auxiliary plants. Backhuys Publishers, Leiden, Netherlands. pp. 214–217.

Other references

• Drinkall, M.J. & Price, T.V., 1986. Studies of the infection of the winged bean by Synchytrium psophocarpi in Papua New Guinea. Annals of Applied Biology 109: 87–94.

• Gunasekera, S.A., Shanthichandra, W.K.N. & Price, T.V., 1990. Disease incidence, severity and pod yield of winged bean (Psophocarpus tetragonolobus) accessions and Psophocarpus scandens. Tropical Pest Management 36(3): 207–210.

• Harder, D.K., 1992. Chromosome counts in Psophocarpus. Kew Bulletin 47(3): 529–534.

• Klauer, S.F., Franceschi, V.R., Ku, M.S.B. & Zhang, D.-Z, 1996. Identification and localization of vegetative storage proteins in legume leaves. American Journal of Botany 83(1): 1–10.

• Mackinder, B., Pasquet, R., Polhill, R. & Verdcourt, B., 2001. Leguminosae (Papilionoideae: Phaseoleae). In: Pope, G.V. & Polhill, R.M. (Editors). Flora Zambesiaca. Volume 3, part 5. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 261 pp.

• Mulongoy, K. & Akobundu, I.O., 1992. Agronomic and economic benefits of N contributions by legumes in live-mulch and alley cropping systems. IITA Research 1(4): 12–16.

• Tong, T.H., Tjong, J.K. & Lubis, I.P., 1961. Psophocarpus palustris - an ideal ground cover for oil palm and rubber. Proceedings of the national rubber research conference, 26 September – 1 October 1960, Kuala Lumpur. Rubber Research Institute of Malaysia, Kuala Lumpur, Malaysia. pp. 312–324.

Sources of illustration

• Verdcourt, B. & Halliday, P., 1978. A revision of Psophocarpus (Leguminosae - Papilionoideae - Phaseolae). Kew Bulletin 33(2): 191–227.

Author(s)

• R.R. Schippers

De Boeier 7, 3742 GD Baarn, Netherlands

Correct citation of this article

Schippers, R.R., 2004. Psophocarpus scandens (Endl.) Verdc. [Internet] Record from PROTA4U. Grubben, G.J.H. & Denton, O.A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. <http://www.prota4u.org/search.asp>.

Accessed 6 March 2025.

• See the Prota4U database.