Sunn Hemp, Slender Leaf Rattlebox, Marejea

Crotalaria ochroleuca
Fabaceae – Pea


Sunn Hemp originated in tropical Africa.


Sunn Hemp is a versatile green manure crop used to improve the soil, suppress weeds, feed livestock, and control erosion. It is especially suited from fruit groves because, unlike vining ground covers, you don’t need to worry about it covering up the trees. It is currently being grown in banana, plantain, citrus, and coconut groves. This species may have some usefulness in suppressing nematodes when used in rotation with other crops. The seeds are used to keep weevils from stored rice and maize.


This species of Sunn Hemp is a vigorous upright (non-vine) legume growing to 2 m (6 ft) in height. The seeds, about the size of millet seeds, are mixed with two parts of coarse sand and broadcast by hand. They do not need to be covered, although it would be a good idea to well to draw a branch across the newly planted field. You should plant no less than 10 kg (22 lb) of seed per acre. They sprout after a few days and develop a strong root. Growth is rather slow until they reach about one foot, then they quickly grow to 2 m (6 ft) or more. Crotolaria ochroleuca is fairly drought tolerant, recovering well when rains return. If planted densely in a well-prepared field, this should be all the work required (except to keep out animals).

Harvesting and Seed Production

Sunn Hemp can be cut about 3 months after planting; if it is cut back to about one foot (30 cm) above the ground, it will regrow. After it is cut, it can be left in the field as mulch or used as fodder. Later in the season cattle can be allowed to graze the Sunn Hemp, but only for short periods of time, so that they do not overgraze it. Plants bear seed after 3–4 months and die after 6 months. Seeds should not be stored in a closed room where people are working. Please note: if you need to order large quantities of seed, write to Fr. Gerold Rupper, St. Benedict’s Abbey, PO Box 1, Peramiho, Tanzania, East Africa. Seed is US$7/kg, including postage and phytosanitary certificates.

Pests and Diseases

To protect bags of stored grain, spread Sunn Hemp seeds on the ground and place the bags on top of the seeds. Continue layering seed and bags of grain; this will be effective for about 9 months.

Cooking and Nutrition

The broad leaves and broad pods have a mild taste. Crotalaria ochroleuca is usually eaten with cowpeas or pumpkin leaves; occassionally it is eaten on its own. The flowers can also be eaten.