Bobgunnia madagascariensis

Family: Fabaceae (Caesalpinoideae)
Synonym: Swartzia madagascariensis 

This species was placed in the Swartzia genus previously, before being moved to the current genus: Bobgunnia. The tree is one of 10 hardwood timber species – including Mpingo – that are responsibly managed and traded by the rural communities that MCDI support in south-eastern Tanzania. It is known as msekeseke in Swahili and ‘snake bean’ tree in English due to the shape of its pods. It is traded as Pau rosa.

The Tree

B. madagascariensis trees are usually small with a rounded grown. The grey bark is thick and rough with longitudinal cracks. For several months each year the tree is bare, although the cylindrical chocolate-brown seed pods remain and make it quite distinctive. When damaged the tree exudes a dark-coloured gum with a pea-like scent. The leaves have an uneven number (imparapinnate) of greyish coloured leaflets with yellow hairs on the underside. The tree bears fragrant, pale, pea-like flowers; these are followed by pods which release 10-15 seeds when the sticky yellow flesh around them rots on the ground. 

Ecology & Distribution

B. madagascariensis is widely distributed across wooded habitats in Africa. Most specimens in Kilwa District occur in intact miombo woodland, often on sandy soil. Despite its scientific name, B. madagascariensis does not occur in Madagascar. 

Timber

The heartwood of B. madagascariensis is dark reddish-brown or purplish. Growth rings, varying in colour from yellow to dark brown, form bands in a zigzag arrangement that makes the timber very decorative. The wood varnishes well (although stains do not always penetrate sufficiently), takes a high polish, and works to a fine finish. The heartwood is highly resistant to insects and has powerful fungicidal properties.

Physical & Woodworking Properties
Density (kg/m3)Very high (960-1,100) MachiningDifficult
Hardness (kgf)Very high (1,334)PlaningModerate
DurabilityVery highMovement in serviceModerate
GrainMedium-interlockedResistance to splittingHigh
TextureMedium-fineResistance to fungiVery high
ScrewingDifficultResistance to insectsVery high

Uses

Timber

B. madagascariensis produces a dark, fine-grained timber suited for turnery and carving. As the timber sometimes turns purply black, it has been recorded as a substitute for mpingo. The wood weathers well and has resonance characteristics which make it suitable for various musical instruments. There is much logging interest in the tree in Kilwa District as a result of these qualities.

Other uses

B. madagascariensis makes excellent slow-burning firewood and is popular for making charcoal. Various parts of the tree are used in traditional medicine. The pods are nitrogen-rich food for cattle.