Guibourtia coleosperma (PROTA)

Plant Resources of Tropical Africa Introduction

List of species

General importance
Geographic coverage Africa
Geographic coverage World
Cereal / pulse
Fruit
Vegetable oil
Dye / tannin
Medicinal
Timber
Fuel
Ornamental
Forage / feed
Food security

Guibourtia coleosperma (Benth.) J.Léonard

Protologue: Bull. Jard. Bot. Etat 19: 403 (1949).

Family: Caesalpiniaceae (Leguminosae - Caesalpinioideae)

Chromosome number: 2n = 48

Vernacular names

African rosewood, bastard teak, Rhodesian teak, bastard mopane, large false mopane, large mock mopane, copalwood, Rhodesian mahogany (En). Copalier, copalier de Rhodésie (Fr).

Origin and geographic distribution

Guibourtia coleosperma occurs naturally in southern DR Congo, Zambia, Angola, Namibia, Botswana and Zimbabwe.

Uses

The wood of Guibourtia coleosperma is used for construction, flooring, joinery, interior trim, furniture, mine props, ship building, vehicle bodies, railway sleepers, toys, novelties, tool handles, turnery and decorative veneer. It is traditionally used for canoes. It is an appreciated firewood.

The seed and its aril contain oil, which is used for cooking. The red dye from the aril has been used for staining furniture. The seeds are eaten, especially during times of food shortage, often after roasting and pounding. The arils are also eaten or used to make a nourishing drink. They are cooked with cassava leaves as a relish. The bark is used for tanning and dyeing. Guibourtia coleosperma is an appreciated ornamental tree, with striking flowers and fruits, which show up against the dark glossy foliage, and providing deep shade. In traditional medicine, the roots are applied to wounds to promote healing and a root decoction is used as cure for venereal diseases. Young leaves are taken to treat cough and leaf decoctions are administered after childbirth to promote recovery and to treat stomach complaints. A decoction of roots and bark is administered as a vapour bath to treat headache, whereas roots and leaves are ingredients in mixtures for the treatment of fever and mental problems.

Production and international trade

The wood of Guibourtia coleosperma is traded on the international timber market in small amounts. It is reported that about 500 m³ per year is available from sustainably managed forest and woodland.

Properties

The heartwood is pinkish brown or pale red-brown with pinkish or reddish stripes, darkening to a rich mahogany-like red-brown colour with the stripes becoming more faint. It is clearly demarcated from the yellowish white to pale pink, up to 9 cm wide sapwood. The grain is straight or interlocked, texture moderately fine and even. The wood has an attractive figure. It has a fragrant smell when freshly cut.

The wood is heavy, with a density of (670–)800–960 kg/m³ at 12% moisture content. It air dries slowly; drying should be done with care to avoid excessive warping and splitting. The sawn timber can be kiln dried at a moderate speed and temperature. The rates of shrinkage are moderate, from green to oven dry 2.0–3.7% radial and 3.2–5.7% tangential.

At 12% moisture content, the modulus of rupture is 85–142 N/mm², modulus of elasticity 9210 N/mm², compression parallel to grain 51–58 N/mm², compression perpendicular to grain 14 N/mm², shear 14–16 N/mm², cleavage 20 N/mm, Janka side hardness 8820–9065 N and Janka end hardness 9800–11,150 N.

The wood saws and works well despite its high density and hardness. It finishes well although the presence of interlocked grain may sometimes cause picking up of grain in planing. It polishes well. Pre-boring is needed for nailing and screwing. The gluing and varnishing properties are satisfactory, but staining may be difficult. Veneer of good quality can be produced by slicing and rotary peeling. The wood is moderately durable to durable, being moderately resistant to fungal attack and resistant to termite attack. The sapwood is susceptible to Lyctus borers. The heartwood is resistant to preservative treatment.

The seeds have an oil content of about 6.5% and a protein content of 14.5%. The heartwood contains proguibourtinidins (with and without stilbenoid constituent units), profisetinidins and derived compounds. Flavonoid glycosides have been isolated from the bark.

Adulterations and substitutes

Much of Guibourtia coleosperma timber is mixed with that of Baikiaea plurijuga Harms, traded as ‘mukusi’ or ‘Zambezi teak’. The two species grow in the same vegetation type and the wood is similar in appearance and characteristics.

Description

Semi-evergreen medium-sized tree up to 30 m tall; bole branchless for up to 15 m, up to 65(–125) cm in diameter, slightly buttressed or fluted at base; bark surface smooth or sometimes flaking, grey to pinkish cream, inner bark reddish; crown rounded, large; young branches reddish brown, glabrous. Leaves arranged spirally, paripinnately compound with 1 pair of leaflets; stipules 1–2 cm long, early caducous; petiole 1.5–4 cm long; leaflets nearly sessile, obliquely ovate or elliptical, 3.5–12 cm × 2–6 cm, base cuneate, apex usually acuminate, glabrous, with numerous translucent dots, pinnately veined with 7–11 pairs of lateral veins, 1–3 of which from base of leaflet. Inflorescence an axillary or terminal panicle up to 12 cm long, nearly glabrous; bracts up to 2 mm long, very early caducous. Flowers bisexual, zygomorphic, whitish to creamy, fragrant; pedicel 2–5 mm long; sepals 4(–5), unequal, 5–6 mm × 1.5–4 mm, hairy inside; petals absent; stamens 10, free, up to 7 mm long; ovary superior, rounded, c. 1 mm in diameter, glabrous, 1-celled, with short stipe, style 4–5 mm long. Fruit an obliquely elliptical, flattened pod 2–3.5 cm × 1.5–2 cm, glabrous, wrinkled and brown, tardily dehiscent, 1-seeded. Seed ellipsoid, somewhat flattened, 1–2 cm long, dark brown, shiny, completely enclosed by red aril, hanging out of dehisced fruit on a thread-like funicle. Seedling with epigeal germination; cotyledons nearly rounded, leafy.

Other botanical information

Guibourtia comprises about 14 species, all African, but a single species occurs in tropical America. The genus is related to Hymenaea and Peltogyne.

Anatomy

Wood-anatomical description (IAWA hardwood codes):

• Growth rings: 1: growth ring boundaries distinct.
• 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; 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; 69: fibres thin- to thick-walled.
• Axial parenchyma: 78: axial parenchyma scanty paratracheal; 79: axial parenchyma vasicentric; (80: axial parenchyma aliform); (81: axial parenchyma lozenge-aliform); (83: axial parenchyma confluent); 86: axial parenchyma in narrow bands or lines up to three cells wide; 89: axial parenchyma in marginal or in seemingly marginal bands; 91: two cells per parenchyma strand; 92: four (3–4) cells per parenchyma strand; 93: eight (5–8) cells per parenchyma strand.
• Rays: 98: larger rays commonly 4- to 10-seriate; 104: all ray cells procumbent; 115: 4–12 rays per mm.

(F.D. Kamala, P.E. Gasson & E.A. Wheeler)

Growth and development

Guibourtia coleosperma is slow growing, with a mean annual increase in bole diameter of about 3 mm. In an experimental plantation in Zimbabwe of 16 years old, mean annual height increment was only 14–21 cm and survival only 5%. Coppice shoots reach about 1 m long in one year. The tree is usually leafless for short periods only and often nearly evergreen. Flowering is from December to March. The seeds can be harvested from (May–)June to October. The bright red arils attract birds such as glossy starlings and parrots as well as monkeys, which feed on them and thereby disperse the seeds. Lateral roots were found at a depth of 10–60 cm in Zimbabwe, but the taproot can reach a depth of 10 m or more. Endomycorrhizae are associated with the roots.

Ecology

Guibourtia coleosperma occurs in woodland and dry forest, often along rivers, at 750–1400 m altitude. It is found in areas with a mean annual temperature of 20–28°C and an annual rainfall of (450–)650–1100 mm. It is often one of the dominant species in the upper storey together with Baikiaea plurijuga Harms and Pterocarpus angolensis DC., which are also important timber species. It is almost exclusively found on Kalahari sand soils, which are deep and infertile with a low water-holding capacity. Guibourtia coleosperma is sensitive to fire and somewhat insensitive to frost, although frost may cause severe damage to seedlings and saplings.

Propagation and planting

Guibourtia coleosperma can be propagated by seeds, cuttings or root suckers. Seed production is reported to vary considerably from year to year, and is mainly influenced by the amount and distribution of rainfall. The 1000-seed weight is about 275 g. Germination usually starts within 10 days after sowing. In Botswana germination tests using fresh, untreated seeds gave a 95% germination rate. Shelter and adequate moisture are essential for a high survival rate of seedlings. In experimental plantations, spacings of 2 m × 2 m to 5 m × 5 m have been practised.

Management

In southern DR Congo Guibourtia coleosperma is locally common, with 5–6 trees per ha. Controlled early burning in May of the undergrowth and litter layer has been tested and was found useful to avoid the more detrimental burning in September. Trees may produce root suckers and coppice shoots when cut. Guibourtia coleosperma is occasionally planted. In plantations regular weeding is required for at least the first 3 years.

Diseases and pests

In the nursery, the seedlings are susceptible to spider mites, especially under glass. The foliage is browsed by elephants and antelopes, but serious damage has not been reported.

Harvesting

Boles with a minimum diameter of 35 cm have been harvested from natural woodland in a cutting cycle of 40 years. In Zimbabwe, the recommended minimum bole diameter for Guibourtia coleosperma as well as Baikiaea plurijuga is 50 cm. Selective logging did not aggravate erosion problems because the Kalahari soils allow high infiltration and have a gradient of only 1% or less. However, it may lead to increased fire hazards. Regeneration after logging was satisfactory. However, elsewhere it was observed that regeneration of Guibourtia coleosperma after harvesting was not adequate, whereas that of Baikiaea plurijuga was more than adequate; this would result in a shift towards more dominance of the latter species in the vegetation.

Handling after harvest

Logs should not be left in the forest for longer periods or should be treated with insecticides because the sapwood is liable to insect attacks. The oil is extracted by pounding and boiling the seeds. People in Botswana and Zambia remove arils with warm water.

Genetic resources

Guibourtia coleosperma is widely distributed with no apparent threats, but in Namibia and Botswana it is legally protected.

Prospects

Although Guibourtia coleosperma is a useful multipurpose tree that provides timber and non-timber products such as edible seeds and traditional medicine, no attempts have been made to domesticate it or exploit its genetic variation. Efforts to explore its potential for plantations are urgently needed, although the low growth rates seem to limit its prospects as a plantation timber tree of economic importance, as well as a timber tree that can be harvested from natural forest on a sustainable basis. Little information is available on management practices and therefore research in this area is needed.

Major references

• Brummitt, R.K., Chikuni, A.C., Lock, J.M. & Polhill, R.M., 2007. Leguminosae, subfamily Caesalpinioideae. In: Timberlake, J.R., Pope, G.V., Polhill, R.M. & Martins, E.S. (Editors). Flora Zambesiaca. Volume 3, part 2. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 218 pp.

• Burke, A., 2006. Savanna trees in Namibia - factors controlling their distribution at the arid end of the spectrum. Flora Jena 201(3): 189–201.

• CAB International, 2005. Forestry Compendium. Guibourtia coleosperma (large false mopane). [Internet] http://www.cabicompendium.org/ fc/datasheet.asp?ccode=guibco. February 2011.

• Calvert, G.M., 1986. The ecology and management of Kalahari Sand Forest vegetation of south-Western Zimbabwe. In: Piearce, G.D. (Editor). The Zambezi teak forests: proceedings of the first international conference on the teak forests of Southern Africa, Livingstone, Zambia. 18–24th March 1984. Forest Department, Ndola, Zambia. pp. 121–158.

• Coates Palgrave, K., 2002. Trees of southern Africa. 3rd Edition. Struik Publishers, Cape Town, South Africa. 1212 pp.

• Fanshawe, D.B., 1962. Fifty common trees of Northern Rhodesia. Lusaka, Zambia. 108 pp.

• Högberg, P., 1986. Rooting habits and mycorrhizas of Baikiaea plurijuga. In: Piearce, G.D. (Editor). The Zambezi teak forests: proceedings of the first international conference on the teak forests of Southern Africa, Livingstone, Zambia. 18–24th March 1984. Forest Department, Ndola, Zambia. pp. 92–102.

• Storrs, A.E.G., 1979. Know your trees: some of the common trees found in Zambia. Forest Department, Ndola, Zambia. 380 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.

• Wilczek, R., Léonard, J., Hauman, L., Hoyle, A.C., Steyaert, R., Gilbert, G. & Boutique, R., 1952. Caesalpiniaceae. 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 3. Institut National pour l’Étude Agronomique du Congo belge, Brussels, Belgium. pp. 234–554.

Other references

• Anonymous, 1964. Guibourtia coleosperma. Informations techniques no 186, Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 1 pp.

• Anonymous, 1979. Timbers of Zambia: Ficalhoa laurifolia, Guibourtia coleosperma. Division of Forest Products Research, Kitwe, Zambia. 4 pp.

• Bekker, M., Bekker, R. & Brandt, V.E., 2006. Two flavonoid glycosides and a miscellaneous flavan from the bark of Guibourtia coleosperma. Phytochemistry 67(8): 818–823.

• Calvert, G.M., 1986. Growth summaries, sample plot 1, Gwaai Forest. In: Piearce, G.D. (Editor). The Zambezi teak forests: proceedings of the first international conference on the teak forests of Southern Africa, Livingstone, Zambia. 18–24th March 1984. Forest Department, Ndola, Zambia. pp. 198–201.

• Fanshawe, D.B., 1972. Useful trees of Zambia for the agriculturist. Ministry of Lands and Natural Resources. Government Printer, Lusaka, Zambia. 126 pp.

• Fox, F.W. & Norwood Young, M.E., 1988. Food from the veld: edible wild plants of southern Africa botanically identified and described. Delta Books, Craighall, South Africa. 422 pp.

• Holdo, R.M. & Timberlake, J., 2008. Rooting depth and above-ground community composition in Kalahari sand woodlands in western Zimbabwe. Journal of Tropical Ecology 24: 169–176.

• Leger, S., 1997. The hidden gifts of nature: A description of today’s use of plants in West Bushmanland (Namibia). [Internet] DED, German Development Service, Windhoek, Namibia & Berlin, Germany. http://www.sigridleger.de/book/. November 2010.

• Léonard, J., 1949. Notulae Systematicae IV (Caesalpiniaceae-Amherstieae africanae americanaeque). Bulletin du Jardin botanique de l'Etat (Bruxelles) 19(4): 383–408.

• Léonard, J., 1950. Etude botanique des copaliers du Congo belge. INEAC, série scientifique no 45. Bruxelles, Belgium. 158 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.

• Ross, J.H., 1982. Caesalpinioideae. In: de Winter, B., Killick, D.J.B., Leistner, O.A. & Ross, J.H. (Editors). Flora of Southern Africa 16(2). Department of Agricultural Technical Services, Pretoria. Republic of South Africa. 142 pp.

• SEPASAL, 1999. Survey of Economic Plants for Arid and Semi-Arid Lands. [Internet] Royal Botanic Gardens, Kew, Richmond, United Kingdom. http://www.kew.org/ ceb/sepasal/. November 2010.

• Storrs, A.E.G., 1982. More about trees: a sequel to "Know your trees". Forest Department. Ndola, Zambia. 127 pp.

• Tietema, T., Merkesdal, E. & Schroten, J., 1992. Seed germination of indigenous trees in Botswana. African Centre for Technology Studies, Nairobi, Kenya. 106 pp.

• van Vuuren, N.J.J., Banks, C.H. & Stohr, H.P., 1978. Shrinkage and density of timbers used in the Republic of South Africa. Bulletin No 57. South African Forestry Research Institute, Pretoria, South Africa. 55 pp.

• van Wyk, B. & van Wyk, P., 1997. Field guide to trees of southern Africa. Struik Publishers, Cape Town, South Africa. 536 pp.

• Watt, J.M. & Breyer-Brandwijk, M.G., 1962. The medicinal and poisonous plants of southern and eastern Africa. 2nd Edition. E. and S. Livingstone, London, United Kingdom. 1457 pp.

• White, F., 1962. Forest flora of northern Rhodesia. Oxford University Press, London, United Kingdom. 455 pp.

Sources of illustration

• Ross, J.H., 1982. Caesalpinioideae. In: de Winter, B., Killick, D.J.B., Leistner, O.A. & Ross, J.H. (Editors). Flora of Southern Africa 16(2). Department of Agricultural Technical Services, Pretoria. Republic of South Africa. 142 pp.

Author(s)

• W. Mojeremane, Department of Crop Science and Production, Botswana College of Agriculture, Private Bag 0027, Gaborone, Botswana

• I. Kopong, Department of Crop Science and Production, Botswana College of Agriculture, Private Bag 0027, Gaborone, Botswana

Correct citation of this article

Mojeremane, W. & Kopong, I., 2011. Guibourtia coleosperma (Benth.) J.Léonard. In: 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. Accessed 18 December 2024.

• See the Prota4U database.