Sarawak Bean
Vigna hosei

Family: Fabaceae

What it is like

Sarawak Bean, Vigna hosei, is a perennial plant producing twining stems 1-2 m long that scrambles over the ground or twine into any surrounding vegetation. Although no plant part is edible and of medicinal important, the plant is an excellent ground cover and green manure crop. Seedling growth is vigorous and young plants quickly suppress growth of weed. It also has the ability to fix atmospheric nitrogen, hence it enriches the oil and promotes plant growth.

Vigna hosei is a PERENNIAL CLIMBER growing to 1 m (3ft 3in) by 0.2 m (0ft 8in) at a fast rate. See above for USDA hardiness. It is hardy to UK zone 10. The plant is self-fertile. It can fix Nitrogen. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils. Suitable pH: mildly acid soils and can grow in very acid soils. It can grow in semi-shade (light woodland) or no shade. It prefers moist or wet soil.

Height (m): 1

Where it is found

Not known as a wild plant. Naturalized in southern china, where it grows in grass at roadsides, wastelands; at elevations below 500 metres.

Native to Taiwan, Indonesia and Malaysia in tropical southeast Asia. It is also widely cultivated an

Conservation Status: Status: Data Deficient

Countries/locations it is found in

How it is used

Food

Rating: 0

Medicine

Rating: 0

Other

Rating: 4

Agroforestry Uses: The plant is used as a green manure and ground cover crop in young tree plantations, and also in rubber, tea and coconut plantations. Seedling growth is vigorous and young plants quickly suppress weed growth, forming a thick mat of growth with a dense leaf litter, which protects the soil from erosion and prevents the ingress of weeds. Its ability to fix atmospheric nitrogen enriches the soil and promotes the growth of the trees. Due to its persistence under shade, the plant can enrich a mixture of leguminous covers for young plantation trees. Being a low-growing creeper, it hardly climbs trees, which is considered important for a good cover crop. The plant is also being trialled as a green manure in association with annual crops. When sown as a cover crop it may be mixed with other leguminous covers such as Calopogonium mucunoides, Centrosema pubescens and Pueraria phaseoloides. Other Uses None known

Green manure: Fast-growing plants that can be used to increase the fertility of the soil.

Soil stabilization: Plants that can be grown in places such as sand dunes in order to prevent erosion by wind, water or other agents.

Food Forest: Plants for Edible Forest Gardens and Food Forests.

Ground Cover: Ground Cover

Nitrogen Fixer: Plants that fix nitrogen in the soil

How it is grown

A plant of the wet tropics, where it is found at elevations up to 1,100 metres. It grows best in areas where annual daytime temperatures are within the range 22 - 30°c, but can tolerate 15 - 35°c. It does not tolerate frosts. It prefers a mean annual rainfall in the range 3,000 - 3,500mm, but tolerates 2,500 - 4,000mm. Succeeds in full sun and in light shade. Succeeds in sandy to clayey soils and is tolerant of occasional waterlogging. Prefers a pH in the range 4.5 - 5, tolerating 4 - 5.5. The plant has a shallow root system and a low tolerance of drought. Flowering commences about 6 months after planting, self-pollination is the rule. An outstanding characteristic of the plant is its persistence under shade, but full sunlight is required for good seed production. Seed production is often poor and only about 50 kilos per hectare can be harvested. Harvesting the seed on a field scale is also difficult. Besides producing normal aerial flowers and pods, the plant also produces flowers and pods which are hidden under the litter of leaves covering the soil. A ground cover of Vigna hosei can be removed easily by hoeing the soil, followed by a clean weeding. 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. Although non-specific in its Rhizobium requirement, inoculation is preferably carried out with a selected cowpea strain such as CB 756.

Propagating it: Seed - it has a hard seedcoat and may benefit from scarification before sowing to speed up germination. This can usually be done by pouring a small amount of nearly boiling water on the seeds (being careful not to cook them!) and then soaking them for 12 - 24 hours in warm water. By this time they should have imbibed moisture and swollen - if they have not, then carefully make a nick in the seedcoat (being careful not to damage the embryo) and soak for a further 12 hours before sowing. Prior to sowing, the seeds may be inoculated with compost containing an appropriate Rhizobium strain Cuttings - it is recommended to plant during the rainy season and to use 20cm long, 3-noded cuttings planted 100 - 150cm apart.

Best place to grow:

Habit: Perennial Climber

Hardiness: 10-12

Growth: Fast

Soil: Light (sandy), medium, heavy (clay)

Shade: Semi-shade, no shade

Moisture: Moist, wet

Things to keep in mind

Its other names

Local names

Synonyms

Dolichos hosei Craib Vigna oligosperma Backer Vigna parkeri acutifolia Verdc. Vigna parkeri acutifol