Lablab purpureus Seeds | Dolichos
LATIN NAME: Lablab purpureus
COMMON NAME: Hyacinth Bean
Plant Profile
Lablab purpureus is a vigorous climbing bean with purple stems, purple-veined leaves and sprays of pea-like flowers in pink or violet. The pods are flat, curved and glossy, and they turn from green to purple as they mature. It grows as an annual in temperate climates and as a short-lived perennial in the tropics, and it can cover a fence or a pergola in a season.
The species has been grown in Africa and in Asia for thousands of years, and its origin is debated, with the evidence pointing to Africa. It is a multi-purpose crop: the seed is eaten, the vine is cut for fodder, and the plant is used as a green manure and as a cover crop. In Asia the young pod is eaten as a vegetable, and in Africa the mature seed is more important.
Science & Biotechnology
The mature seed contains phytohaemagglutinin, the same lectin found in red kidney beans, and it must be soaked and boiled before it is safe to eat. The young pod is eaten whole and is less of a problem, but the dried seed needs thorough cooking. The plant also contains cyanogenic compounds in the leaf in some varieties, which is why fodder is usually wilted before it is fed.
The vine is drought-tolerant and deep-rooted, and it fixes nitrogen. It is one of the legumes that can be grown on residual moisture after a cereal crop, and it is used in rotation to improve soil structure. The genus is close to the African lablab landraces, which are more diverse than the Asian ones, and breeding has focused on day-length neutrality so that the crop can be grown outside the tropics.
Uses & Benefits
The young pod is eaten as a vegetable, and the mature seed is cooked in stews and in soups. The vine is cut for fodder for cattle and goats, and the plant is used as a green manure and as a cover crop. In some districts the flower is eaten and the root is used as a medicine.
In Ayurveda and in Chinese medicine the seed is used as a tonic and for stomach complaints, and the pod is used for diarrhoea. The plant is also grown as an ornamental for the purple flowers and pods, particularly the dark-leaved forms sold as a curiosity.
Growing from Seed
Soak the seed overnight and sow it at 20 to 25 degrees in spring, one per pot. Germination is in one to two weeks. Plant out after the last frost, and provide a strong support, since the vine is heavy.
The plant wants full sun and a well-drained soil, and it tolerates drought once established. It is tender below about zero, so it is grown as an annual in cool climates. Harvest the pods young for eating, or leave them to dry for seed, and cook the mature seed thoroughly before eating it. Do not overwater, since the vine resents wet feet.
Our Take
A generous, drought-proof climbing bean for a fence or a pergola, useful as food, fodder and green manure, with a seed that must be boiled.
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