Prota 7(1): Timbers/Bois d’œuvre 1
Bull. Misc. Inform. Kew 1910: 180 (1910).
2n = 72
Entandrophragma stolzii Harms (1917).
Origin and geographic distribution
Entandrophragma excelsum occurs in eastern DR Congo, Rwanda, Burundi, Uganda, Tanzania, Malawi and Zambia.
The wood is suitable for construction, flooring, joinery, interior trim, furniture, cabinet work, musical instruments, vehicle bodies, toys, novelties, boxes, crates, carvings, turnery, veneer and plywood. It is also used as firewood and for charcoal production.
In Burundi ash made from root bark is rubbed into scarifications to treat blood cough. In Tanzania the roots are used to treat gonorrhoea and hernia. Entandrophragma excelsum is planted as a roadside tree. It is also planted in agroforestry systems as a shade tree.
Production and international trade
Entandrophragma excelsum is not harvested on a large scale as commercial timber. It has been of some importance in Burundi, but officially felling is no longer allowed.
The heartwood is pinkish brown when freshly cut, darkening to reddish brown, and is usually distinctly demarcated from the pinkish white to pale brown, up to 5 cm wide sapwood. The grain is interlocked, sometimes straight, texture medium. Quarter-sawn surfaces show a stripe figure, which is often irregular.
The wood is moderately lightweight, with a density of 460–530 kg/m³ at 12% moisture content. Logs are generally straight and cylindrical, but susceptible to severe star shakes and heavy checking on the end surfaces after felling because tension wood is often present. The wood air dries rather slowly, with 2.5 cm thick boards taking 2 months to dry from green to 15% moisture content. Careful stacking and weighting down is needed because the wood is liable to severe warping, cupping and distortion. Quarter-sawing before drying is recommended. Great care is needed to obtain satisfactory results in kiln drying. The rates of shrinkage are medium to high, from green to oven dry 3.1–5.6% radial and 8.1–12.4% tangential. Once dry, the wood is moderately stable in service.
At 12% moisture content, the modulus of rupture is 50–108 N/mm², modulus of elasticity 6800–9900 N/mm², compression parallel to grain 32–43 N/mm², shear 8–10 N/mm², cleavage 11–13 N/mm and Janka side hardness 2050 N.
The wood saws and works fairly easily with both hand and machine tools; it has only slight blunting effects on cutting edges. In planing and moulding operations a 15–25° cutting angle is recommended to avoid picking up of grain. The use of a filler is needed to obtain a good finish. The wood is difficult to drill cleanly and only the smaller sizes of square chisels can be used. The nailing, screwing and gluing properties are satisfactory, but nail-holding power is poor. Staining may give poor results on quarter-sawn surfaces, which can be overcome by the use of a filler. The wood is suitable for the production of sliced and rotary veneer, and can be made into plywood of satisfactory quality.
The wood is not durable, being liable to powder-post beetle, pinhole borer, termite and marine borer attacks. The heartwood is resistant to preservatives and the sapwood moderately resistant.
Deciduous, dioecious large tree up to 45(–60) m tall; bole branchless for up to 27 m, straight and cylindrical, up to 200(–250) cm in diameter, with large buttresses up to 5 m high; bark surface greyish with pale orange patches and smooth, becoming irregularly scaly with scales leaving shallow pits, inner bark reddish with white streaks; crown rounded or dome-shaped; young twigs brownish short-hairy. Leaves alternate, clustered near ends of twigs, paripinnately compound with 8–16 leaflets; stipules absent; petiole 9–23 cm long, scarcely flattened, rachis 10–45 cm long, glabrous; petiolules up to 10 mm long; leaflets opposite or nearly so, oblong-elliptical, 8–18(–30) cm × 4.5–8(–14) cm, rounded and slightly asymmetrical at base, usually short-acuminate at apex with often reflexed point, papery to thinly leathery, glabrous, pinnately veined with 8–14 pairs of lateral veins. Inflorescence an axillary or terminal panicle up to 25(–45) cm long, short-hairy. Flowers unisexual, regular, 5-merous; pedicel 2–4 mm long; calyx cup-shaped, lobed to about the middle, 1.5–2 mm long, sparsely short-hairy outside; petals free, elliptical, 5–7 mm long, glabrous or sparsely short-hairy outside, white or pinkish white; stamens fused into an urn-shaped tube 3–4 mm long, with 10 anthers at the entire or wavy apex; disk cushion-shaped, indistinct; ovary superior, flask-shaped, 5-celled, style very short, stigma disk-shaped; male flowers with rudimentary ovary, female flowers with smaller, non-dehiscing anthers. Fruit a pendulous, cylindrical capsule 12–20(–25) cm × 3–4 cm, dark brown to purplish black, with many small lenticels, dehiscing from the base with 5 woody valves, up to 30-seeded with seeds attached to the upper part of the central column.
The winged seeds are dispersed by wind, although most of them seem to fall close to the mother tree.
Entandrophragma comprises about 10 species and is confined to tropical Africa. It belongs to the tribe Swietenieae and is related to Lovoa, Khaya and Pseudocedrela.
The wood of several other Entandrophragma spp. is locally and/or occasionally used in Central, East and southern Africa. Entandrophragma bussei Engl. is a medium-sized tree up to 20 m tall, endemic to Tanzania, where it occurs in deciduous thickets, woodland and bushland at 800–1200 m altitude. The wood is reddish brown and heavy, with a density of about 850 kg/m³ at 12% moisture content. It works easily and takes a good finish, but does not take nails well. The wood is locally used for furniture, beehives and milk containers. It is suitable for construction, flooring, joinery, interior trim, ship building, vehicle bodies, toys, novelties, boxes, crates, turnery, veneer and plywood. The bark is used medicinally in cases of problems of milk production in nursing mothers.
Entandrophragma caudatum (Sprague) Sprague (mountain mahogany) is a medium-sized tree up to 30 m tall, occurring from Malawi, Zambia and Mozambique to South Africa. The wood is reddish brown or dark brown and moderately heavy, with a density of 700–815 kg/m³ at 12% moisture content. The rates of shrinkage from green to oven-dry are low, 3.1% radial and 5.5% tangential. The wood is locally in demand for furniture, cabinet work and canoes, but supply is limited. The bark has been used for dyeing and tanning, and showed in-vitro antiplasmodial activity.
Entandrophragma delevoyi De Wild. is a fairly large tree up to 35 m tall, occurring in DR Congo, Tanzania and Zambia in dry evergreen forest and riverine forest. The wood is moderately heavy with a density of about 660 kg/m³ at 12% moisture content. It is locally used for house construction, as firewood and for charcoal production. Entandrophragma delevoyi is planted as an ornamental shade tree and roadside tree.
Entandrophragma palustre Staner is a fairly large tree up to 30(–40) m tall and up to 100(–150) cm in diameter, characteristic of swamp forest in Congo and DR Congo (and probably elsewhere in Central Africa). The wood is reddish brown and moderately heavy, with a density of 580–750 kg/m³ at 12% moisture content. It is fairly difficult to saw. The wood is suitable for construction, joinery, interior trim, furniture, cabinet work, toys, novelties, boxes, crates, carvings and sliced veneer. The bark is used in traditional medicine to treat stomach-ache, kidney pains, rheumatism, haemorrhoids, scabies, otitis and eye inflammation.
Entandrophragma excelsum occurs in mid-altitude and montane rainforest, at (1000–)1300–2150 m altitude. It is locally also found in riverine forest.
Seeds can be stored for some time in sealed containers in a cool place, but insect damage, to which they are very susceptible, should be avoided, e.g. by adding ash. Soaking of the seeds for one night is reported to speed up germination. Overhead shade is required for young seedlings.
In tests in Rwanda, Entandrophragma excelsum was shown to be useful as a shade tree in agroforestry systems; particularly soya bean grew prolifically under the trees.
Genetic resources and breeding
Although Entandrophragma excelsum populations are not exploited on a commercial basis, they may become threatened by habitat loss. Entandrophragma excelsum is included in the IUCN Red List, but is still considered to be at lower risk of genetic erosion.
The wood of Entandrophragma excelsum is not in much demand for local applications because it often warps and twists considerably upon drying. Moreover, it is not durable and not very attractively figured. Its occurrence in mountain regions often hampers commercial exploitation. However, Entandrophragma excelsum may be interesting for wider-scale planting in agroforestry programmes in higher-altitude regions. More research is needed on growth rates, propagation and planting.
• Bolza, E. & Keating, W.G., 1972. African timbers: the properties, uses and characteristics of 700 species. Division of Building Research, CSIRO, Melbourne, Australia. 710 pp.
• Katende, A.B., Birnie, A. & Tengnäs, B., 1995. Useful trees and shrubs for Uganda: identification, propagation and management for agricultural and pastoral communities. Technical Handbook 10. Regional Soil Conservation Unit, Nairobi, Kenya. 710 pp.
• Staner, P. & Gilbert, G., 1958. Meliaceae. In: Robyns, W., Staner, P., Demaret, F., Germain, R., Gilbert, G., Hauman, L., Homès, M., Jurion, F., Lebrun, J., Vanden Abeele, M. & Boutique, R. (Editors). Flore du Congo belge et du Ruanda-Urundi. Spermatophytes. Volume 7. Institut National pour l’Étude Agronomique du Congo belge, Brussels, Belgium. pp. 147–213.
• Styles, B.T. & White, F., 1991. Meliaceae. In: Polhill, R.M. (Editor). Flora of Tropical East Africa. A.A. Balkema, Rotterdam, Netherlands. 68 pp.
• Takahashi, A., 1978. Compilation of data on the mechanical properties of foreign woods (part 3) Africa. Shimane University, Matsue, Japan, 248 pp.
• Egli, A.E., 1994. Einfluss ausgewählter Standortsfaktoren in Abhangigkeit von zehn nicht Stickstoff fixierenden Baumarten auf die Erträgsbildung wichtiger Feldfrüchte unter agroforstlichen Anbaubedingungen. Ein Beispiel aus Butare/Rwanda (Ost-/Zentralafrika). Forstwissenschaftliche Beiträge ETH Zürich 13. 206 pp.
• Fouarge, J., Sacré, E. & Mottet, A., 1950. Appropriation des bois congolais aux besoins de la métropole. Série Technique No 38. Institut National pour l’Étude Agronomique du Congo belge (INEAC), Brussels, Belgium. 17 pp.
• Louis, J. & Fouarge, J., 1950. Essences forestières et bois du Congo. Fascicule 4. Entandrophragma palustre. Institut National pour l’Etude Agronomique du Congo belge (INEAC), Brussels, Belgium. 75 pp.
• Msangi, T.H., 1991. The medicinal plants of Tanzania as a genetic resource. A survey and assessment of conservation strategies. MSc thesis, School of Biological Sciences, University of Birmingham, Birmingham, United Kingdom. 96 pp.
• Neuwinger, H.D., 2000. African traditional medicine: a dictionary of plant use and applications. Medpharm Scientific, Stuttgart, Germany. 589 pp.
• Palmer, E. & Pitman, N., 1972–1974. Trees of southern Africa, covering all known indigenous species in the Republic of South Africa, South-West Africa, Botswana, Lesotho and Swaziland. 3 volumes. Balkema, Cape Town, South Africa. 2235 pp.
• Parant, B., Chichignoud, M. & Curie, P., undated. Présentation graphique des caractères technologiques des principaux bois tropicaux. Tome 8. Bois du Burundi. CTFT, Nogent-sur-Marne, France. 82 pp.
• Tanzania Forest Division, 1962. Timbers of Tanganyika: Entandrophragma stolzii (mrie). Tanzania Forest Division, Utilisation Section, Moshi, Tanzania. 4 pp.
• Troupin, G., 1982. Flore des plantes ligneuses du Rwanda. Publication No 21. Institut National de Recherche Scientifique, Butare, Rwanda. 747 pp.
• van Wyk, B.E. & Gericke, N., 2000. People’s plants: a guide to useful plants of southern Africa. Briza Publications, Pretoria, South Africa. 351 pp.
Correct citation of this article:
Lemmens, R.H.M.J., 2008. Entandrophragma excelsum (Dawe & Sprague) Sprague. In: Louppe, D., Oteng-Amoako, A.A. & Brink, M. (Editors). Prota 7(1): Timbers/Bois d’œuvre 1. [CD-Rom]. PROTA, Wageningen, Netherlands.