Vigna subterranea (L.) Verdc.

International Legume Database and Information Service

Conservation

Not Threatened

Ecology

Africa: Cultivated, Sudanian woodland

Morphology General Habit

Annual, Not climbing, Herb

Vernacular

Bambara, Bambara Bean, Bambara Groundnut, Bambarra Groundnut, Mani Congo, Ouange, Pistache Malgache, Voanjabory, Voanjobory

Extinction risk predictions for the world's flowering plants to support their conservation (2024). Bachman, S.P., Brown, M.J.M., Leão, T.C.C., Lughadha, E.N., Walker, B.E. https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.19592

Conservation

Predicted extinction risk: not threatened. Confidence: confident

Morphology Reproductive morphology Seeds Protein Content

18.00% Entire seed/nut. Moisture content not stated (Vaughan, 1970)

Kew Species Profiles

General Description

Bambara groundnut (Vigna subterranea) is an important grain legume which grows in the semi-arid regions of Africa. Its ability to fix nitrogen and its resistance to high temperatures and drought makes it a valuable crop in areas where soils are too poor for other leguminous crops to grow. By burying its fruits in the soil it protects them from insect damage which can devastate other crops such as cowpea, common bean and soybean, whose tastiest parts are above ground.

Bambara groundnut is very nutritious, boasting a 65% carbohydrate content and an 18% protein content, making it an important addition to the diets of people who cannot afford expensive animal protein. It is considered to be a complete food and people can survive exclusively on bambara groundnut for all of their nutritional needs.

Bambara groundnut is a lifesaver during the hungry season, the period that exists when the old crops have been eaten and the new crops have not yet been harvested. Despite all of these benefits it is a much underutilised and has the potential to be more than just a subsistence crop. Part of the problem is its stigma as a 'poor person's crop'. 

Species Profile

Geography and distribution

Bambara groundnut most likely originated in north-eastern Nigeria and northern Cameroon, where it can still be found growing wild today. It is cultivated throughout tropical Africa and to a lesser extent in the tropical parts of the Americas, Asia and Australia. 

Habitat

Bambara groundnut grows best in dry areas with sandy soils. It is also well suited to upland areas such as the highlands of Zambia and Zimbabwe. Bambara groundnut can produce a reasonably good yield in humid regions, although the dampness makes it susceptible to fungal diseases and the plant needs careful handling. 

Description

Vigna subterranea is a leafy, annual, creeping legume with glabrous (hairless) leaves supported by a petiole 5-30 cm long. Each leaf is composed of three leaflets (trifoliolate) and can be up to 11 cm long. 

Yellow flowers are clustered 1-3 on an unbranched axis, known as a raceme. They are papilionaceous, typical of species belonging to the subfamily Papilionoideae, and resemble, for example, the pea flower. The peduncle (the stalk supporting the raceme) is up to 3 cm long, hairy and after flowering it expands and bends downwards so that the fruits develop underground.

The ovary, which develops into the seed pod, contains 1-4 ovules. Once mature the seeds, which can be of various colours, are almost spherical and are 8-15 mm in diameter. Bambara groundnut has a deep taproot surrounded by lateral roots bearing nitrogen-fixing nodules.

Threats and conservation

Vigna subterranea is not considered to be threatened in the wild and its conservation status is of least concern (LC). 

Uses

Bambara groundnut is cultivated mainly for its seeds which can be boiled, roasted or fried to make a delicious snack or mixed in with maize or plantains to serve as a meal. The seeds can be ground into flour after roasting and used to prepare porridge or they can be soaked, boiled and ground into a paste and used in fried or steamed dishes popularly eaten in Nigeria. The flour can also be used as a thickener in soups and stews and in Zambia it is commonly made into bread. Milk can be made from the seeds and fermented products similar to tempeh and dawadawa can be prepared.

Besides being a food crop, the seeds and leafy shoots of bambara groundnut, which are rich in protein and phosphorus make good fodder for pigs and poultry.

Bambara groundnut also has a number of medicinal uses. In Senegal: 

leaf preparations are applied as a poultice for infected wounds and abscessesleaf sap is applied to the eyes as a treatment for epilepsypounded seeds mixed with water are used to treat cataractsthe roots of the plant can be taken as an aphrodisiac

Evidence suggests that high fibre foods such as bambara groundnut can reduce the incidence of heart disease and help to prevent colon cancer.

Bambara groundnut improves the quality of the soil because of its ability to fix nitrogen from the air. It is therefore a good companion in crop rotations.

Crop wild relatives of bambara groundnut

The Millennium Seed Bank and the Global Crop Diversity Trust are engaged in a ten-year project, called 'Adapting Agriculture to Climate Change'. The project aims to protect, collect and prepare the wild relatives of 29 key food crops, including bambara groundnut, so that they are available to pre-breeders for the development of new varieties that are more resilient to the effects of climate change.

Its ability to fix nitrogen and its resistance to high temperatures and drought makes bambara groundnut a valuable crop with enormous potential to be grown on a larger scale, providing food security for many more people. 

Millennium Seed Bank: Seed storage

The  Millennium Seed Bank Partnership aims to save plants worldwide, focusing on those plants which are under threat and those which are of most use in the future. Once seeds have been collected they are dried, packaged and stored at -20°C in Kew's Millennium Seed Bank vault.

Description of seeds:  Average weight of 1,000 seeds = 585 g

Number of seed collections stored in the Millennium Seed Bank:  One

Seed storage behaviour:  Orthodox (the seeds of this plant can be dried to a low moisture content without significantly reducing their viability. This means they are suitable for long-term frozen storage)

Germination testing:  Successful

This species at Kew

Pressed and dried specimens of bambara groundnut are held in Kew's Herbarium, where they are available to researchers by appointment. Details and images of some of these specimens can be seen online in Kew's Herbarium Catalogue.

Distribution

Cameroon, Niger

Ecology

Bambara groundnut grows best in dry areas with sandy soils. More information below.

Conservation

Common in the wild and in cultivation and thus not globally threatened.

Leguminosae, J. B. Gillett, R. M. Polhill & B. Verdcourt. Flora of Tropical East Africa. 1971

Morphology General Habit

Annual herb with short compact to long loose sparsely pubescent densely leafy creeping stems.

Morphology Leaves

Leaves held erect; leaflets elliptic, obovate or oblanceolate, 3–8 cm. long, 0·8–4 cm. wide, rounded or emarginate at the apex, cuneate at the base; petiole 2–30 cm. long; rhachis (0·1–)1–2·5 cm. long; petiolules 1–3 mm. long; stipules ovate, 3 mm. long.

Morphology Reproductive morphology Inflorescences

Racemes 1–3-flowered; peduncle 0·5–2 cm. long.

Morphology Reproductive morphology Flowers Calyx

Calyx glabrous; tube ± 1 mm. long; lobes ±1 mm. long.

Morphology Reproductive morphology Flowers Corolla

Standard yellow, obovate, 4–7 mm. long.

Morphology Reproductive morphology Fruits

Pods 1–2·2 cm. long, 1·2–1·8 cm. wide, glabrous.

Morphology Reproductive morphology Seeds

Seeds variously coloured white, yellow, red or blackish or variously mottled, longest dimension 8·5–15 mm., shorter dimension 6·5–10 mm.

Papilionaceae, Hutchinson and Dalziel. Flora of West Tropical Africa 1:2. 1958

Morphology Reproductive morphology Flowers

Flowers usually in pairs on a peduncle, stigma lateral.

Seed Collecting Guide. RBG Kew (2013-2016)

Morphology General Habit

Annual herbs

Morphology Stem

stem short and creeping, sparsely pubescent, densely leafy, internodes short, 0.5-5.5 cm long. trifoliolate, held erect, 6-11 x 1-4.5 cm, petiole 5-30 cm long, rhachis 1-2.5 cm long, leaflets elliptic, obovate or oblanceolate, rounded or emarginate at the apex, cuneate at the base, glabrous

Morphology Leaves Stipules

stipules c. 3 mm long, ovate, slightly bilobed at the base, striate, multinerved

Morphology Reproductive morphology Inflorescences

peduncle 0.5-3 cm x 0.2-0.8 mm, pubescent, expanding and bending downwards after flowering so that the fruits develop underground; rhachis usually 1-noded

Morphology Reproductive morphology Flowers

flower yellow, 9.5-12 x 8-10.5 mm, pedicel 1-5 mm long, expanding as the pod matures, bracteoles c. 2.5 x 0.5 mm, 1-nerved flower: calyx glabrous, tube 1 mm long, lobes 1 mm long, loWest lobe slightly longer than others, the upper pair of lobes joined to form a bifid lip standard with 2 obscure central appendages, keel open on the upper side, slightly twisted towards the right, without a beak

Morphology Reproductive morphology Flowers Gynoecium Ovary

ovary 1-4-ovuled

Morphology Reproductive morphology Fruits

fruit: pods 1-3.5 x 1-1.8 cm, irregularly oblong-ovoid, shortly beaked with a recurved style base, glabrous

Morphology Reproductive morphology Seeds

variously coloured, 8.5-15 mm in diameter, almost spherical or truncate if several seeds are present

Morphology Reproductive morphology Seeds Hilum

hilum elliptic, aril very reduced.

Use

Food, fodder, medicine.