Jack bean, Canavalia ensiformis, is a tropical American bean grown in India mainly as a cover crop and green manure. Its young pods can be cooked as a vegetable, but its raw seeds are toxic. It holds a special place in science: the first enzyme ever crystallised, urease, and the lectin concanavalin A both came from jack bean seeds.
- Botanical name
- Canavalia ensiformis (L.) DC.
- Family
- Fabaceae
- Tamil
- Kattuthambattai
- Hindi
- Bara sem
- Parts used
- Young pods (cooked), Seeds (long-cooked, caution)
- Habit
- Jack bean; sword bean is C. gladiata
- Last updated
- 2026-10-26
How to recognise Jack bean
It is a bushy or semi-climbing annual with leaves of three broad, oval leaflets.
Flowers are pink to purple, in clusters on long stalks.
The pods are long, flat and sword-like, up to thirty centimetres, holding large white seeds with a brown scar.
Sword bean, Canavalia gladiata, is a climbing relative with longer pods and usually red or pink seeds.
Traditional use of Jack bean
Farming
It is grown as a cover crop and green manure in plantations and orchards, and as fodder.
Indian farm practice
Kitchen
Young, tender pods are sliced and cooked as a vegetable in some regions.
Tropical food practice
Modern notes on Jack bean
In 1926 the chemist James Sumner crystallised urease from jack bean, showing that enzymes are proteins, work that later won a Nobel Prize.
The seeds contain canavanine and lectins such as concanavalin A, which are toxic if eaten raw or undercooked.
Jack bean safety
Do not eat raw or undercooked seeds. Even young pods should be cooked thoroughly.
Ecology and sourcing
It is native to Central and South America and grown throughout the tropics.
Its deep roots and nitrogen-fixing ability make it a good soil-improving crop.
It tolerates drought and poor soils.
In plantations it is sown between rows of tree crops to cover and feed the soil.
Related plants
Also in Fabaceae
Questions about Jack bean
Is Jack bean sword bean?
No. Sword bean is Canavalia gladiata.
Are the seeds of Jack bean edible?
Not raw. They contain toxic compounds.
Why is Jack bean famous in science?
Urease, the first crystallised enzyme, came from jack bean.
Can the young pods be eaten?
Yes, when young and thoroughly cooked.
Sources
- Canavalia ensiformis (L.) DC. — Plants of the World Online, Kew (search) (accessed 2026)
- Wikidata item Q1677262 (Canavalia ensiformis)
Educational page about a plant. It is not medical advice, not a diagnosis, and not an offer to sell. Traditional use is historical. If you need care, ask a licensed clinician. Questions: hello@meevamed.com.