African yam bean Sphenostylis stenocarpa
African yam bean (Sphenostylis stenocarpa) is an evergreen perennial vegetable in the Fabaceae family, native to Tropical Africa (West Africa to Ethiopia and south to Zimbabwe). It grows 1.5–3 m (4.9–10 ft) tall and 50 cm–1 m (20 in–3.3 ft) wide, wants full sun and moderate water, and is hardy to about 8 °C (46 °F). Space plants about 60 cm (24 in) apart.
Plan African yam bean in your garden →
Free. Draw your beds, then watch it grow through the year in 2D and 3D.
African yam bean at a glance
| Type | Perennial vegetable, evergreen |
|---|---|
| Family | Fabaceae |
| Mature height | 1.5–3 m (4.9–10 ft) |
| Mature spread | 50 cm–1 m (20 in–3.3 ft) |
| Spacing | 60 cm (24 in) centre to centre |
| Sun | Full sun, at least 6 h of direct sun a day |
| Water | Moderate; drought tolerance moderate, waterlogging tolerance none |
| Soil pH | 5–7 |
| Cold hardiness | About 8 °C (46 °F) once established (roughly USDA zone 11) |
| Heat stress | Likely above about 36 °C (97 °F) |
| Flowering | about 13–17 weeks after planting, for 4–9 weeks |
| Wind tolerance | Low |
| Pollinator value | Moderate |
| Edible | Yes: dry seeds (after long cooking), tuberous roots (cooked), young pods, leaves |
| Native to | Tropical Africa (West Africa to Ethiopia and south to Zimbabwe) |
| Common in gardens of | 🇳🇬 Nigeria, 🇪🇹 Ethiopia |
Is African yam bean toxic?
- People: mildly toxic
- Cats: not well documented
- Dogs: not well documented
- Parts: raw seeds
The seeds are very hard and contain trypsin inhibitors and other antinutrients: soak and boil them for hours. Not poisonous when properly cooked.
If a child or pet may have eaten part of a plant, call a poison centre or vet straight away.
Companion planting: what to grow with African yam bean
Good neighbours
- good With Sweet corn: "Three sisters": climbing beans use corn as a support and fix nitrogen; the benefit to the corn is modest but real in low-input soils. Evidence C
Keep apart or take care
- caution With Alliums (onion family): Onions, garlic and leeks are said to stunt beans and peas (allium root exudates may reduce nodulation). Traditional companion-planting advice; controlled trials are few, so treat it as a soft preference. Evidence D
- caution With Alliums (onion family): Beans and peas are traditionally kept away from onions, garlic and leeks. Traditional companion-planting advice; controlled trials are few, so treat it as a soft preference. Evidence D
- caution With Fennel: Fennel is reported to suppress beans and peas growing next to it. Evidence C
Questions about African yam bean
- How far apart should I plant African yam bean?
- About 60 cm (24 in) apart, centre to centre. A mature plant spreads 50 cm–1 m (20 in–3.3 ft).
- Does African yam bean need full sun?
- Full sun: at least 6 hours of direct sun a day.
- How much water does African yam bean need?
- Moderate water. Drought tolerance is moderate and waterlogging tolerance none.
- How cold-hardy is African yam bean?
- It tolerates about 8 °C (46 °F) once established, roughly USDA zone 11.
- When does African yam bean flower?
- About 13–17 weeks after planting, for 4–9 weeks.
- Is African yam bean poisonous to cats and dogs?
- For cats it is not well documented; for dogs not well documented; for people mildly toxic. The seeds are very hard and contain trypsin inhibitors and other antinutrients: soak and boil them for hours. Not poisonous when properly cooked.
- What grows well with African yam bean?
- "Three sisters": climbing beans use corn as a support and fix nitrogen; the benefit to the corn is modest but real in low-input soils.
Sources and evidence
Evidence grade B (B: extension service or peer-reviewed).
- Plants of the World Online (taxonomy, native range), Royal Botanic Gardens, Kew
- Lost Crops of Africa, vol. I Grains (1996), II Vegetables (2006), III Fruits (2008), National Research Council, National Academies Press, Washington DC
- PROTA4U: Plant Resources of Tropical Africa, PROTA Foundation, Wageningen
Notes and assumptions
- Tropical: needs warm nights all year; in a frosty climate grow it under glass or as a summer container plant.
- A twining bean grown up stakes or yam poles in south-eastern Nigeria: long pods with mottled seeds above ground, and in some forms spindle-shaped edible tubers below.
Reference values for planning, not horticultural, veterinary or medical advice. Varieties, soils and local climates differ: check with a local nursery or extension service.
Related plants
- Bush bean Phaseolus vulgaris
- Garden pea Pisum sativum
- Sweet pea Lathyrus odoratus
- Runner bean Phaseolus coccineus
- Broad bean (fava) Vicia faba
- Lima bean Phaseolus lunatus
- Cowpea (black-eyed pea) Vigna unguiculata
- Yardlong bean Vigna unguiculata subsp. sesquipedalis