Prota 7(1): Timbers/Bois d’œuvre 1
London Journ. Bot. 3: 88 (1844).
Mimosaceae (Leguminosae - Mimosoideae)
Muanza (Po). Mkenge maji, mgelenge (Sw).
Origin and geographic distribution
Albizia glaberrima is widespread from Guinea Bissau east to Kenya and south to Angola, Zimbabwe and Mozambique; also in Comoros and western Madagascar.
The wood of Albizia glaberrima (trade name in Uganda: white nongo) is used for furniture in Uganda. In Tanzania it is used for construction, stools, beehives, tool handles and grain mortars, and in Malawi for doors, beds and implements (e.g. mortars). It is also suitable for light and heavy flooring, interior trim, joinery, mine props, shipbuilding, vehicle bodies, railway sleepers, toys and novelties, boxes and crates, carving and plywood making. The wood serves as firewood and for charcoal production. In Uganda Albizia glaberrima is considered a good shade tree for coffee, tea, banana and cocoa plantations. The foliage is used as forage for livestock. The flowers are a bee forage.
In southern Nigeria the bark is applied externally to treat fever. In Tanzania a cold water extract of the root bark is used to treat bilharzia, and in Benin a root decoction in a mixture with other plant ingredients is used as a bath to treat anaemia. In Cameroon the dried pulverized twig bark is applied to scarifications to treat blenorrhagia, a decoction of the twig bark is drunk against chest pain, and ash of burned roots is applied to scarifications to treat liver complaints.
The heartwood varies from dirty white to reddish brown, sometimes with darker stripes, and is distinctly demarcated from the white sapwood, which is up to 7.5(–10) cm wide. The grain is straight, sometimes interlocked, texture moderately coarse.
The wood is moderately heavy, with a density of about 660 kg/m³ at 8.5% moisture content. It dries slowly, but with little degrade. At 8.5% moisture content, the modulus of rupture is 93 N/mm², modulus of elasticity 11,400 N/mm², compression parallel to grain 55 N/mm², shear 13 N/mm², Janka side hardness 5300 N and Janka end hardness 5910 N.
The wood saws and works well, with little blunting of saw teeth and tool edges. A reduced cutting angle is required to prevent tearing in planing operations. A filler is needed to obtain a smooth finish. The nailing, screwing and gluing properties are satisfactory. The wood does not turn well. It is moderately durable, with some resistance to termite attack, but susceptible to pinhole borers and marine borers. The heartwood is resistant to impregnation by preservatives, the sapwood permeable.
Medium-sized deciduous tree up to 30 m tall; bole straight and cylindrical or irregular, up to 100 cm in diameter; bark surface grey, smooth or shallowly fissured, often with numerous lenticels; crown flattened, umbrella-shaped; young twigs shortly hairy. Leaves alternate, bipinnately compound with 1–3(–4) pairs of pinnae; stipules awl-shaped, caducous; petiole 2–4.5 cm long, grooved above, shortly hairy, with a sessile gland near the middle of upper side, rachis 2–4 cm long, sparsely pubescent; leaflets in 3–7(–8) pairs per pinna, with petiolules 0.5–2 mm long, obliquely rhombic-ovate, up to 7(–9) cm × 3(–4) cm, obtuse to acute at apex, minutely pubescent to almost glabrous. Inflorescence an axillary head on 2–4 cm long peduncle. Flowers bisexual, regular, 5-merous, white; pedicel 1.5–7 mm long, finely greyish hairy; calyx 1.5–2.5 mm long, with long tube toothed at apex, pubescent outside; corolla 3–5.5 mm long, with 2–3 mm long tube, pubescent outside; stamens numerous, 6–13 mm long, united at base, filaments white; ovary superior, 1.5–2 mm long, with c. 0.5 mm long stipe, gradually tapering into an up to 12 mm long style. Fruit an oblong, flat pod 12–26 cm × 3–4 cm, with stipe up to 8 mm long, pubescent or almost glabrous, indistinctly transversely veined, glossy or dull brown when ripe, opening with 2 papery valves, c. 10-seeded. Seeds flattened globose to ellipsoid, 8–12 mm × 6–8 mm. Seedling with epigeal germination.
Albizia glaberrima trees grow slowly. They form N-fixing root nodules. The pod valves with seeds still attached are spread by wind.
Albizia comprises about 120 species and occurs throughout the tropics. Approximately 35 species are found in continental Africa and about 30 in Madagascar. It is characterized by the head-like inflorescence, with 1–2 central flowers modified, functionally male and having a larger, nectar-producing staminal tube. Molecular analyses have shown that Albizia is heterogeneous, and a revision of the genus is needed. Albizia glaberrima is often confused with Albizia zygia (DC.) J.F.Macbr., which differs in its sessile leaflets. Albizia glaberrima is variable and 3 varieties have been distinguished, of which var. glaberrima and var. glabrescens (Oliv.) Brenan (synonym: Albizia glabrescens Oliv.) are widespread, the former from Guinea Bissau to Sudan and Uganda, and the latter from DR Congo and Kenya to Zimbabwe, Mozambique and Madagascar. The lower side of var. glaberrima leaflets is minutely pubescent, that of var. glabrescens leaflets glabrous. Var. mpwapwensis Brenan is intermediate and only known from Tanzania.
In West and Central Africa Albizia glaberrima occurs most commonly in semi-deciduous forest, but sometimes also in logged-over evergreen forest. In Cameroon it is characteristic of secondary forest. In East Africa it can be found in lowland rainforest, riverine forest and evergreen bushland, in Madagascar in deciduous woodland.
Seeds should be collected before the pods dehisce, which makes collecting difficult. They can be stored for up to 3 months, but are liable to weevil attacks; adding ash reduces insect damage. To obtain good germination, seeds can be immersed in boiling water, allowed to cool, and soaked in water for 24 hours before sowing. The seedlings are classified as non-pioneer light demanders. Wildlings are sometimes collected in the forest for planting. Planted trees can be managed by coppicing and pollarding. Logs may have brittle heart and tension wood seems to be rather frequent. The logs have to be treated with a preservative soon after felling to prevent insects attacking the sapwood.
Genetic resources and breeding
Albizia glaberrima is widespread and locally common, and not threatened by genetic erosion.
Little is known about Albizia glaberrima, probably partly because it is uncommon in several countries within its distribution area, and partly because it is confused with other Albizia spp. As a multipurpose species it deserves more attention in agroforestry programmes.
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Correct citation of this article:
Lemmens, R.H.M.J., 2007. Albizia glaberrima (Schumach. & Thonn.) Benth. In: Louppe, D., Oteng-Amoako, A.A. & Brink, M. (Editors). Prota 7(1): Timbers/Bois d’œuvre 1. [CD-Rom]. PROTA, Wageningen, Netherlands.