African Yam Bean
Sphenostylis stenocarpa

Family: Fabaceae

What it is like

African Yam Bean, Sphenostylis stenocarpa, is a tropical, fast-growing climbing vine growing up to 2 m in height from a tuberous rootstock. Its leaves are comprised of three leaflets each of 14 cm long and 5 cm wide. The flowers can be pink, purple, or greenish-white, occurring in the axils of the leaves. Seed pods are flat and smooth. This species has no medicinal uses. However, it is cultivated as food source particularly for its pods and roots. Immature seedpods and the seeds are cooked and used as a vegetable. The roots, high in protein, can also be consumed either raw or cooked. Similarly, the leaves are also cooked and consumed as a vegetable. This species has a symbiotic relationship with certain soil bacteria that form nodules on the roots and fix atmospheric nitrogen.

Sphenostylis stenocarpa is a PERENNIAL CLIMBER growing to 2 m (6ft) by 0.3 m (1ft in) at a fast rate. See above for USDA hardiness. It is hardy to UK zone 10. It can fix Nitrogen. Suitable for: light (sandy) and medium (loamy) soils and prefers well-drained soil. Suitable pH: mildly acid and neutral soils and can grow in very acid soils. It cannot grow in the shade. It prefers moist soil.

Height (m): 2

Where it is found

Brachystegia woodland, riparian and lakeshore bushland, grassland, roadsides, often in rocky places and on termite mounds, at elevations of 10 - 1,500, occasionally 2,000 metres.

Tropical Africa - Guinea to Ethiopia and south to Angola, Zimbabwe and Mozambique

Conservation Status: This taxon has not yet been assessed

Countries/locations it is found in

Africa, Angola, Burkina Faso, Burundi, Cameroon, Central Africa, Chad, Congo, Côte d'Ivoire, East Africa, Ethiopia*, Ghana, Guinea, Guinée, Ivory Coast, Kenya, Malawi, Mozambique, Nigeria, Southern Africa, Tanzania, Togo, Uganda, West Africa, Zambia, Zimbabwe.

How it is used

Food

Rating: 4

Immature seedpods - cooked and used as a vegetable. The pods are up to 25cm long and 15mm wide. Seeds - cooked. Rich in protein, they are boiled and eaten as a vegetable, or added to soups etc. The seed is about 9mm long. Root - raw or cooked. The white fleshed roots can be cooked like potatoes, which they resemble in taste. They are rich in protein. Leaves - cooked and used as a vegetable.

Root: includes bulbs, corms, tubers, rhizomes etc.

Seed: includes nuts, cereals, peas and beans.

Seedpod: things such as Okra, French and Runner beans.

Medicine

Rating: 0

Other

Rating: 0

This species has a symbiotic relationship with certain soil bacteria that form nodules on the roots and fix atmospheric nitrogen.

Agroforestry Services: Nitrogen: Plants that contribute to nitrogen fixation include the legume family – Fabaceae.

Management: Standard: Plants grow to their standard height. Harvest fruit, seeds, or other products. Non-Destructive management systems.

Regional Crop: These crops have been domesticated and cultivated regionally but have not been adopted elsewhere and are typically not traded globally, Examples in this broad category include perennial cottons and many nuts and staple fruits.

Staple Crop: Protein: (16+ percent protein, 0-15 percent oil). Annuals include beans, chickpeas, lentils, cowpeas, and pigeon peas. Perennials include perennial beans, nuts, leaf protein concentrates, and edible milks.

Agroforestry Services: Nitrogen: Plants that contribute to nitrogen fixation include the legume family – Fabaceae.

Management: Standard: Plants grow to their standard height. Harvest fruit, seeds, or other products. Non-Destructive management systems.

Carbon Farming: Plants that can be a critical part of the solution to climate problems. The Carbon Farming Solution - Eric Toensmeier.

Food Forest: Plants for Edible Forest Gardens and Food Forests.

How it is grown

A plant of the tropics, where it is found at elevations up to 2,000 metres. It grows best in areas where annual daytime temperatures are within the range 23 - 29°c, but can tolerate 15 - 35°c. It prefers a mean annual rainfall in the range 1,000 - 1,200mm, but tolerates 800 - 1,400mm. Requires a dry period when flowering. Prefers a position in full sun. Grows best in a fertile, sandy soil. Prefers a pH in the range 5.5 - 6, tolerating 4.5 - 7. Although perennial, the plant is usually treated as an annual in cultivation. Harvesting of the seedpods can commence about 5 months after sowing, and continue for another 2 months. Tubers mature 7 - 8 months after sowing. Optimum yields of the seed is 2 tonnes per hectare, and of the tubers 4 tonnes. Plants are probably day length sensitive. 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. When removing plant remains at the end of the growing season, it is best to only remove the aerial parts of the plant, leaving the roots in the ground to decay and release their nitrogen.

Propagating it: Seed - sow in situ. Division of tubers.

Best place to grow:

Habit: Perennial Climber

Hardiness: 10-12

Growth: Fast

Soil: Light (sandy), medium

Shade: No shade

Moisture: Moist

Things to keep in mind

Its other names

Local names

Adagora barracha, Amalumbwe, Chinkhoma, Diegemtenguere, Girigiri, Ground Squirrel’s bean, Igname haricot, N'taco, Nkhoma, Norouko, Nsama, Odudu, Pempo, african yam bean, akitereku, girigiri, haricot grimpant, haricot igname, igname haricot, kotonosu, kulege, okpo dudu, pomme de terre du mossi, sese, sfenostilo, wild yam bean, yam bean, yam pea.

Synonyms

Dolichos stenocarpus Hochst. Ex A.Rich. Vigna ornata Welw. Ex Baker

African Yam Bean Sphenostylis stenocarpa