Common Name: Hyacinth Bean

General Information

Lablab purpureus is a bushy, or a climbing and branching, herbaceous, short-lived perennial plant that is often grown as an annual. It produces twining stems that can be 6 - 9 metres long[, ]. The plant has a well developed tap-root with many laterals and well developed adventitious roots[].
The plant is best known for its edible seed, though it also has an edible root, leaves, flowers and seedpods. In addition, it has a wide range of medicinal applications and can be used as a green manure. The plant is commonly cultivated, both in home gardens and commercially, in warm temperate to tropical climates for its edible seed, and is also occasionally grown as an ornamental[].

Known Hazards

The raw seed is poisonous[]. Mature seeds have a high content of toxic cyanogenic glucosides and trypsine, and must be thoroughly cooked before eating[]. Cooking completely destroys the toxin[].

Botanical References

Range

Probably originated in the Tropics but has been cultivated for so long that its origins are obscure

Habitat

Not known in a truly wild situation.

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Perennial Climber
Height	3.00 m
Pollinators	Insects
Self-fertile	Yes
Cultivation Status	Cultivated, Ornamental

Cultivation Details

Hyacinth bean can be grown in a wide range of environmental conditions - various strains have been developed that are adapted to different environemnts[]. It grows well in lowland tropical and subtropical areas, but can also succeed when grown up to an elevation of around 2,000 metres[]. In the Temperate zone it grows best when treated as an annual in areas with long hot summers in order to bring the crop to maturity. It grows best in areas where annual daytime temperatures are within the range 18 - 32°c, but can tolerate 3 - 38°c[]. The plant can only tolerate occasional light frosts. It prefers a mean annual rainfall in the range 600 - 1,000mm, but tolerates 200 - 2,500mm[].
Requires a sunny position[]. Easily grown in an ordinary garden soil so long as the temperature is sufficient[]. Succeeds in relatively poor soils so long as they are well-drained[]. Prefers a rich moist soil in a warm sheltered position[]. Prefers a well-drained soil with a high organic matter content and a pH between 5.5 and 6[]. Prefers a pH in the range 5 - 7.5, tolerating 4.5 - 8[]. Some varieties are drought resistant[].
Plants are fairly fast-growing[]
Immature pods are ready to harvest from 70 - 120 days after sowing[]. Mature pods ripen after 140 - 210 days[].
Yields of the dried seed are around 2,200kg per hectare in favourable conditions[].
Optimum yield of green pods is 7.5 tonnes/ha and the average yield in India is 2.6 - 4.5 tonnes/ha[].
There are many named varieties[, , ] varying in height from 60cm to 2 metres.
Short-day, long-day and daylength-neutral varieties are available, day-length-neutral or long-day varieties should be used in temperate climates[, ].
This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[].

Edible Uses

The mature seed is edible as long as it is thoroughly cooked[, , , , , ]. It has a mild flavour, is rich in protein and can be used as a staple food. The seed can also be prepared as 'tofu' or be fermented into 'tempeh' in the same way that soya beans are used in Japan[]. The seed can also be sprouted and eaten raw, when it is comparable to mung bean sprouts[, ]. The seed is up to 12.5mm long[]. A nutritional analysis is available[].

The tender young seedpods and immature seeds can be eaten raw or cooked. They can be used as a green vegetable like French beans[, , ]. They are also used as a curry vegetable[]. The immature seedpod contains 3.2% protein, 0.8% fat, 5.4% carbohydrate, 0.81% ash. It is rich in vitamin B1[]. The seedpods are 5 - 15cm long and 15mm wide[].

Leaves - they must be cooked[, ]. They can also be dried for later use[]. The leaves are used as a greens just like spinach[]. They contain up to 28% protein[, ] (dry weight).

Flowers - raw or cooked in soups and stews[].

Root - large and starchy[].

Medicinal

The plant (though the exact part used is not stipulated) is anticholesterolemic, antidote (to most forms of poison), antivinous, carminative, hypoglycaemic. Prolongs coagulation time[, , ]. It is used in the treatment of cholera, vomiting, diarrhoea, leucorrhoea, gonorrhoea, alcoholic intoxication and globefish poisoning[].

The leaves are antidote, cardiac, emmenagogue and stomachic[]. They are used to accelerate childbirth, to treat stomach troubles and tonsillitis[]. They are combined with the leaves ot other plants and taken in a decoction to treat heart problems[]. They are crushed and sniffed to cure headache[].
The green leaves, crushed in vinegar, have been used to treat snakebites[].

The flowers are antivinous, alexiteric and carminative[].

The stem is used in the treatment of cholera[].

The juice from the pods is used to treat inflamed ears and throats[].

The fully mature seeds are anthelmintic, antispasmodic, aphrodisiac, astringent, digestive, febrifuge and stomachic[, , , , ]. They are used in the treatment of cholera, sunstroke, nausea, vomiting, diarrhoea, enteritis, abdominal pain, alcoholism and arsenic poisoning[]. The seed is well dried and then roasted before use[, ].

Agroforestry Uses:

Plants are fairly fast growing and the bacteria on the roots enrich the soil with nitrogen. This makes them a good green manure crop[, ].
The plant is widely grown for soil improvement and in soil and water conservation programmes. Because of the ease with which various strains of the plant adapt to different environments, the International Institute of Tropical Agriculture (IITA) has promoted its introduction as a cover crop in plantations in humid savannah areas; it also makes a good cover crop in perennial crops such as coffee and coconut[].

Other Uses

A green dye can be obtained from the pounded leaves[].

Propagation

Seed - pre-soak for 2 hours in warm water and sow in early spring in a greenhouse in a fairly rich soil[, ]. Either sow 2 seeds to a pot and thin to the strongest plant, or sow in a tray and prick out into individual pots when the plants are large enough to handle. Grow on fast and plant out after the last expected frosts. The seed germinates in 2 - 4 weeks at 25°c.