Canavalia gladiata Seeds | Sword Bean
LATIN NAME: Canavalia gladiata
COMMON NAME: Sword Bean
Plant Profile
Canavalia gladiata is a vigorous annual climber with a pod that can reach thirty centimetres and a seed that is toxic until it is cooked. The leaves are trifoliate and large, the flowers are pink or white in a long raceme, and the pods are thick, slightly flattened and curved like a sword. The seed inside is red, pink or white, and it is about the size of a large broad bean.
The species is grown across the tropics of Asia and Africa, usually on fences and on the edges of fields, and its origin is uncertain, probably India or the Malay Peninsula. It is a fast-growing legume that fixes nitrogen and produces a large biomass, and it is used as a green manure and as a cover crop as much as for food.
Science & Biotechnology
The raw seed contains concanavalin A, a lectin that binds to sugar residues on cell surfaces and causes red blood cells to clump, together with a trypsin inhibitor. Both are destroyed by thorough boiling, and the seed is safe only after being soaked and boiled for at least half an hour, with the water discarded. Cases of poisoning from undercooked sword bean are well documented.
The plant is robust and drought-tolerant once established, and it is one of the legumes used to suppress weeds and to add nitrogen in rotation. The root system is deep and the vine can cover a fence in a season, which is why it is used as a living trellis and as a windbreak for a vegetable plot.
Uses & Benefits
The seed is eaten after boiling, usually in curries and in soups, and the young pod is eaten as a vegetable in some districts. The mature seed is also roasted and ground as a coffee substitute, and the plant is used as a green manure and as fodder for cattle.
In Chinese and in Ayurvedic medicine the seed and the root are used for a range of complaints, and the pod is used as a poultice. The plant is also grown as an ornamental for the flowers and for the pods, which are striking on a fence.
Growing from Seed
Soak the seed overnight and sow it in spring at 20 to 25 degrees, one per pot, since the seed is large and the seedling resents disturbance. Germination is in one to two weeks. Plant it out when the danger of frost has passed.
The vine needs full sun, a strong support and moderate moisture, and it tolerates poor soil. It is tender below about zero. Grow it on a fence or a trellis at the back of a vegetable plot, and harvest the pods green for eating or leave them to dry for seed. Never eat the seed raw.
Our Take
A vigorous nitrogen-fixing vine with a dangerous seed: useful as a cover crop and as food, but only after a long boil.
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