Jack Bean

Overview

Canavalia ensiformis is a vine native to South and Central America that has been introduced in the tropics and subtropics worldwide. It is grown for food, fodder and as a cover crop or green manure, and is also used as a soil improver and is planted for erosion control. It is usually grown as an annual crop and mainly in Japan and South-East Asia, for its edible seeds and seedpods. The mature seeds contain toxic alkaloids. These can be destroyed by thoroughly boiling the seeds twice in salt water. The seed has been promoted in developing nations as a potential source of affordable and abundant protein.

Vernacular Names

Feve jacques (French), Frijol espada (Spanish), Canavalia (Italian), Jackbohne (German), Fava-branca (Brazilian), Jackbona (Swedish), Bejuco de bibijaguas (Cuba), Haba de burro (Puerto Rican), Swaardboontjie (Afrikaans), Habas (Tagalog-Philippines), Tiehs (Cambodian), Thwâx fak ph'aaz (Laos), Thua khaek (Thai), Dâu tây (Vietnamese), Dao dou (Chinese), Nata-mame (Japanese).

Agroecology

The plant can be grown in temperate to tropical areas at elevations up to 1,500 metres. Prefers a sunny position, but are somewhat shade tolerant. Optimal annual rainfall is between 800-2,000 mm but its deep rooting system allows it to withstand dry periods. It grows best at temperatures between 13 and 27 °C. It can become established in disturbed areas. It can grow continuously under harsh conditions, even in nutrient-depleted, highly leached, acidic soils. C. ensiformis is resistant to drought and pests but does not grow well in excessively wet soil. It will drop its leaves under extremely high temperatures, and can tolerate light frosts. Tolerates a wide range of rainfall (650-2,000 mm) evenly distributed throughout the year. Prefers a pH in the range 5-6, tolerating 4.3-8.

Morphology

• Stems - cylindrical, puberulent, glabrescent, with the pith hollow.
• Leaves - alternate, trifoliolate; leaflets chartaceous, broadly ovate or broadly elliptical, 6-20 × 5-12 cm, the apex obtuse or rounded, short-apiculate, the base obtuse, asymmetrical on the lateral leaflets, the margins entire; both surfaces strigulose, punctate; petiole and rachis cylindrical, glabrescent; petiolules swollen, 8 mm long.
• Flower - inflorescences of axillary pseudoracemes, 25-36 cm long, with 2-3 flowers grouped on the nodal swellings along the rachis; pedicels 1-2 mm long, glabrescent. Calyx green, campanulate, 12-14 mm long, bilabiate; corolla pale violet, 2 cm, the standard and the wings white at the base, violet on the distal portion. Legume linear, up to 30 × 3.5 cm, woody, slightly curved toward the apex, each valve with three longitudinal ribs.
• Pods - produces an average of 7 pods linear, slightly curved, 25 to 30 cm long by 3.5 wide capsules.
• Seeds - 15-20, ellipsoid, up to 3 cm long, white or cream-coloured.

Cultivation

Propagated by seed (generative propagation) - sow in situ, placing the seeds 2-3 cm deep in the soil. The seed germinates in about 72 hours.

Chemical Constituents

Lectin (concanavalin A dan B), tannin, trigonelline, and canavanine.

Traditional Medicinal Uses

• In Nigeria, the seed is used as an antibiotic and antiseptic.
• It is used as a source for the anti-cancer agent.