Agroforestree Database

Local names:
 English (African wild sensitive), Filipino (wild senna)

Senna didymobotrya is usually a several-stemmed shrub or small tree, 0.5-5(-9) m tall.  Branches terete, striate, pubescent to villous, rarely subglabrous.

Leaves simply paripinnate, narrowly oblong-elliptical in outline, 10-50 cm long; stipules broadly ovate-cordate, 6-17 mm x 8-10 mm, acuminate, palmately veined, reflexed, tardily caducous; petiole terete, 1-8 cm long, rachis up to 40 cm long, both pubescent and eglandular; petiolules up to 3 mm long; leaflets in 8-18 pairs, chartaceous, elliptical-oblong, 2-6.5 cm x 0.5-2.5 cm, 2-3 times longer than wide, base oblique, apex rounded but mucronate, pubescent to glabrescent, marginal vein distinct.

Inflorescence an erect, axillary, 20-30 flowered, spike-like raceme, 10-50 cm long; peduncle terete, 5-8 cm long, pubescent; bracts broadly ovate, 8-27 mm x 5-15 mm, black green, at first imbricate and enclosing the flower buds; bracteoles absent; pedicel slender, 3-10 mm long, densely pubescent; sepals 5, subequal, oblong-obovate, 9-14 mm long, puberulous, green; petals 5, slightly unequal, at first incurved,  later on more spreading, ovate to obovate, 17-27 mm x 10-16 mm, with a slender, about 1 mm long claw, glabrous, bright yellow, delicately veined; stamens 10, filaments shorter than anthers, anthers of 2 lower stamens 9-11 mm long, 3 upper stamens staminodial, anthers of 5 median stamens about 5 mm long; ovary and stipe velvety pubescent; style slender, glabrous, recurved, about 1 cm long; stigma punctiform.

Fruit a flat, 9-16 seeded pod, linear-oblong, 7-12 cm x 1.5-2.5 cm, glabrescent, short beaked, dehiscent or indehiscent when dry, depressed between the seeds, sutures raised, blackish-brown.

Seed flattened, oblongoid, apiculate, 8-9 mm x 4-5 mm x 2.5 mm, smooth, pale brown; areole elliptical, 3-4 mm x 0.7-1.5 mm.

In the older literature, this species is best known as Cassia didymobotrya. Until the beginning of the 1980s, Cassia L. was considered to be a genus with over 500 species.

Ecology

In its natural habitat S. didymobotrya is often ruderal in riparian montane wooded grassland or evergreen bushland.  It tolerates light frost.

Native range
Angola, Ethiopia, Kenya, Mozambique, Sudan, Uganda

Tree management

Plantation: When seedling planted as a small shade tree in tea it is spaced at about 5 m x 5 m.

Husbandry: The plants can be lopped several times per year to provide green manure.  Lopping is preferably done when the plants are in flower, when the nutrient content in the leaves is high. The plant yields a fairly large amount of lopping.  About 5 t of green material provides 35.5 kg nitrogen.  In temperate areas, potted ornamental plants are over wintered in greenhouses.

In its natural habitat S. didymobotrya is often ruderal in riparian montane wooded grassland or evergreen bushland.  It tolerates light frost.

S. didymobotrya is easily propagated by seed; cuttings are said not to be successful.  The seed may be sown in the nursery or directly in the field.

Poison: In Africa, it is commonly used as a stupefacient poison for fishing.

Shade or shelter: It has been used as a shade tree in tea plantations.

Medicine: It is widely used as a purgative and an anti-malaria medicine.  A decoction of the leaves is used against stomach complaints. Leaves and roots contain a number of anthraquinones, choline, and the trisaccharide raffinose.

Ornamental: It is now popular as an ornamental plant owing to its bright yellow flowers and black-green bracts.  It is used as ornamental plant in Africa.

Soil improver:  The aboveground biomass of S. didymobotrya grown as ground cover in Sri Lanka was found to contain 0.7 g N per 100 g fresh material. It was introduced as a green manure in India, Sri Lanka, Peninsular Malaysia and Java. It was introduced as a cover crop in India, Sri Lanka, Peninsular Malaysia and Java.

Other services: In sites where Erythrina spp. do not grow well, S. didymobotrya may be a valuable substitute.