Bussea occidentalis (PROTA)

Bussea occidentalis occurs from Guinea eastwards to Ghana.

The wood of Bussea occidentalis, known in trade as ‘samanta’ together with Calpocalyx spp. and Xylia spp., is recommended for heavy construction, industrial flooring, tools, turnery and ornaments. In Liberia it is especially valued for axe handles. Wedges made of Bussea occidentalis wood and used for felling trees proved superior to those made from the wood of other species.

The seeds are eaten after roasting; they are much appreciated in Guinea. In Liberia stem bark is added to palm wine and taken as diuretic. The bark is also used as a medicine for treating sleeping sickness, yellow fever, jaundice and heart troubles. The seeds are also used to treat heart troubles. Bark mixed with maize is used to poison monkeys in Côte d’Ivoire; the same mixture may kill cattle as well. The bark has been used in mixtures to prepare arrow poison. The bark and leaves are used in Côte d’Ivoire as a fish poison. The ash from pods serves as vegetable salt and for making soap.

The timber of Bussea occidentalis is rarely traded on the international market and usually only used locally.

The heartwood is brown to olive brown or dark brown, darkening upon exposure, and distinctly demarcated from the greyish white to pale brown, c. 5 cm wide sapwood. The grain is interlocked, texture moderately coarse.

The wood is heavy, with a density of 870–1090 kg/m³ at 12% moisture content, and very hard. It air dries comparatively rapidly for such a heavy wood; boards of 2.5 cm thick dry to 20% moisture content in about 2 months. End checks may develop during drying. The rates of shrinkage are moderate, from green to oven dry 4.3–6.0% radial and 7.7–9.8% tangential. At 12% moisture content, the modulus of rupture is 156–171 N/mm², modulus of elasticity 19,600–20,480 N/mm², compression parallel to grain 72 N/mm² and Janka side hardness 14,500 N.

The wood is difficult to work with hand tools because of its hardness, but is not difficult to machine. It is rather difficult to plane because of the presence of interlocked grain. However, it takes a good finish. It tends to split upon nailing and pre-boring is needed. The wood glues well and gives good results in turnery. The heartwood is durable, being resistant to termites and borers, but the sapwood is susceptible to Lyctus attack. The wood is resistant to impregnation with preservatives.

The seed coat contains a haemolytic compound and a fish poison. Roasting makes the seeds safe for human consumption. The toxicity of the leaves is attributed to saponins, and the leaves also contain traces of alkaloids. Bark and roots contain tannins.

The amino acid azetidine-2-carboxylic acid has been found in high concentration in the seed, and 3-hydroxyproline and γ-methylglutamic acid are also present. Bark extracts of Bussea occidentalis showed promising in-vitro trypanocidal activity against Trypanosoma brucei rhodesiense with IC₅₀ values below 10 μg/ml. The extract was found to show a modest selectivity index, in contrast to commercially available trypanocides with a more distinct selective toxicity. High cytotoxicity for a human fibroblast cell line (WI-38) has also been reported for a methanol extract of the bark.

In the timber trade Bussea occidentalis is sometimes confused with Peltophorum africanum Sond., which has quite similar wood but a completely different distribution area, from DR Congo southwards throughout a large part of southern Africa. The wood is also similar to that of Erythrophleum suaveolens (Guill. & Perr.) Brenan, which becomes slightly less dark after exposure.

• Evergreen, medium-sized to fairly large tree up to 35(–45) m tall; bole straight and cylindrical to crooked or knotted, up to 75 cm in diameter, often fluted at base, sometimes with small buttresses up to 1 m high; bark surface smooth but with numerous lenticels, slightly scaly in old trees, pale grey to greenish grey, inner bark gritty, pale orange-brown, with copious watery exudate; crown often rounded and small, dense, sometimes with spreading branches; young twigs densely brown short-hairy.
• Leaves alternate, bipinnately compound; stipules needle-shaped, 4–8 mm long, curved inwards, early caducous; petiole c. 10 cm long, jointed at base, rachis ribbed, rusty brown short-hairy; pinnae 4–6 pairs, opposite; petiolules 2–4 mm long; leaflets 12–22 per pinna, alternate, oblong-elliptical to ovate-elliptical, 4–10 cm × 1.5–4 cm, base asymmetrically cuneate, long-acuminate at apex, glabrous.
• Inflorescence an axillary or terminal panicle consisting of dense racemes, up to 30 cm long, densely brown short-hairy.
• Flowers bisexual, slightly zygomorphic, 5-merous, bright yellow, sessile; sepals free, 7–15 mm × 6–8 mm, outside red-brown hairy; petals shortly clawed, one c. 2 cm × 1 cm, other 4 obovate, c. 2.5 cm × 1.5 cm; stamens 10, free, c. 1 cm long; ovary superior, c. 0.5 cm long, sessile, 1-celled, style slender, c. 7 mm long.
• Fruit a woody, narrowly obovate, flattened pod 15–30 cm × c. 3 cm, red-brown short-hairy, dehiscing with 2 valves splitting from top and recurving, 1–2-seeded.
• Seeds elliptical to rounded, flattened, c. 3.5(–5) cm × 2 cm, yellowish brown.
• Seedling with epigeal germination; hypocotyl 5–9 cm long, epicotyl 5–18 cm long; cotyledons sessile, 2–4 cm long, thick and fleshy, rounded at apex; first leaves opposite, paripinnate with 2–3 pairs of leaflets.

Bussea comprises 7 species, 5 of which occur in continental tropical Africa and 2 are endemic to Madagascar. Bussea massaiensis (Taub.) Harms is a shrub or small tree up to 12 m tall, occurring in Tanzania and northern Zambia. Its wood is hard and termite resistant and is used in Tanzania for construction, tool handles, pestles and carvings. The seeds are roasted and eaten as a snack or powdered and added to soup, vegetables or meat. Leaves and seeds are fed to goats and sheep. Bussea massaiensis is useful as ornamental and shade tree.

Bussea perrieri and sakalava

Bussea perrieri R.Vig. and Bussea sakalava Du Puy & R.Rabev. are small to medium-sized trees up to 25 m tall. They are both distributed in dry deciduous forest in Madagascar, where their hard wood is used for construction. The wood of Bussea sakalava is additionally used as firewood, whereas a bark infusion of Bussea perrieri is taken to combat fatigue.

Wood-anatomical description (IAWA hardwood codes):

• Growth rings: 2: growth ring boundaries indistinct or absent.
• Vessels: 5: wood diffuse-porous; 13: simple perforation plates; 22: intervessel pits alternate; 23: shape of alternate pits polygonal; 26: intervessel pits medium (7–10 μm); 29: vestured pits; 30: vessel-ray pits with distinct borders; similar to intervessel pits in size and shape throughout the ray cell; 42: mean tangential diameter of vessel lumina 100–200 μm; 46: ≤ 5 vessels per square millimetre; 47: 5–20 vessels per square millimetre; 58: gums and other deposits in heartwood vessels.
• Tracheids and fibres: 61: fibres with simple to minutely bordered pits; 66: non-septate fibres present; 70: fibres very thick-walled.
• Axial parenchyma: (79: axial parenchyma vasicentric); 80: axial parenchyma aliform; 81: axial parenchyma lozenge-aliform; (83: axial parenchyma confluent); (89: axial parenchyma in marginal or in seemingly marginal bands); 92: four (3–4) cells per parenchyma strand.
• Rays: 97: ray width 1–3 cells; (98: larger rays commonly 4- to 10-seriate); 104: all ray cells procumbent; 115: 4–12 rays per mm.
• Storied structure: 122: rays and/or axial elements irregularly storied.
• Mineral inclusions: 136: prismatic crystals present; 142: prismatic crystals in chambered axial parenchyma cells; (143: prismatic crystals in fibres).

Young trees reached a mean height of 6.5 m and an average bole diameter of 8.5 cm when 7 years old, but the mortality was quite high, about 40%, apparently due to termite attack. In plantations trees may already start fruiting 4 years after planting. Trees flower throughout the rainy period, from May to October, and fruits are ripe in December–January. The fruits open explosively, dispersing the seeds over short distances. The seeds are eaten by colobus monkeys. No nodulation of the roots of Bussea occidentalis has been observed, but association with vesicular-arbuscular mycorrhizae has been recorded.

Bussea occidentalis can be found in all types of forest in its area of distribution, including gallery and secondary forest. It is most frequent in areas with an annual rainfall of 1500–2000 mm. It is locally dominant in the lower and middle storey of the forest and prefers well-drained soils.

Natural regeneration is recorded as poor; numerous seeds germinate but few survive, probably due to poor light conditions and insect attacks. Survival of seedlings is best in small gaps in the forest canopy; the seedlings seem to prefer some shade.

There are about 250 seeds per kg. Seedlings can be easily produced from seeds, which germinate within 1–2 weeks at a germination rate close to 70%. They are easy to grow in the nursery, reaching about 30 cm tall 4 months after sowing, and can be transplanted into the field in full sun. Two-year old stumps transplant well.

In Liberia the total standing stock of Bussea occidentalis trees of more than 50 cm in bole diameter has been estimated at less than 500,000 m³. In Ghana it has been found that where canopy openings were made to encourage natural regeneration, the dense crown of Bussea occidentalis tends to become spreading and to suppress young trees. Careful management is required to obtain straight boles.

In nurseries seedlings of Bussea occidentalis are sometimes attacked by shoot borers, but damage is not serious and the seedlings usually recover.

There is no prescribed minimum bole diameter for felling, but the recommendation in Ghana is 50 cm.

Freshly felled logs sink in water and therefore can not be transported by river.

Although the range of Bussea occidentalis is limited, there are no clear indications that it is threatened at present. There are no known germplasm collections.

The prospects as a timber tree of more economic importance are not bright unless specific applications of the hard wood are developed, for instance for durable parquetry. Availability of larger boles is limited, which hampers exploitation. Planting for seed production might be interesting, but more research on phytochemistry and nutritional value of the seeds is needed. Although promising, the trypanocidal properties of Bussea occidentalis have not been fully explored yet.

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• C.H. Bosch, PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Djagbletey, G.D. & Bosch, C.H., 2011. Bussea occidentalis Hutch. & Dalziel. [Internet] Record from PROTA4U. Lemmens, R.H.M.J., Louppe, D. & Oteng-Amoako, A.A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. <http://www.prota4u.org/search.asp>.

Accessed 6 April 2025.

• See the Prota4U database.