Prota 7(1): Timbers/Bois d’œuvre 1
Bot. Jahrb. Syst. 18: 170 (1894).
Verbenaceae (APG: Lamiaceae)
2n = 32
Origin and geographic distribution
Vitex micrantha occurs from Guinea east to Ghana.
The wood is used on a local scale for light construction, drums and writing boards. It is suitable for light flooring, joinery, interior trim, shipbuilding, furniture, cabinet work, toys, novelties, boxes, crates, veneer, plywood, hardboard, particle board and pulpwood. The fruits are edible and used to make an alcoholic drink. In traditional medicine the leaves are applied externally to treat onchocerciasis (craw-craw), and various parts of the plant are probably used in similar ways to those of Vitex doniana Sweet.
The heartwood is creamy white to pale yellowish brown, darkening on exposure, and indistinctly demarcated from the sapwood. The grain is straight to wavy, texture moderately fine and even. The wood is fairly lustrous. It has a density of about 520 kg/m³ at 12% moisture content. The wood air dries fairly easily. The rates of shrinkage are moderate: from green to oven dry 2.7–2.8% radial and 5.8–6.2% tangential. Once dry, the wood is moderately stable to stable in service.
The wood is soft. At 12% moisture content, the modulus of rupture is 94–124 N/mm², modulus of elasticity 7000 N/mm², compression parallel to grain 46–48 N/mm², cleavage 20 N/mm and Chalais-Meudon side hardness 1.6.
The wood is easy to saw and work with hand and machine tools. It planes to a smooth surface and finishes well. The wood glues satisfactorily. Veneer of good quality can be produced, but the shape of the bole is often too poor for rotary cutting. The wood is not durable and liable to termite, powder post beetle and marine borer attacks. The heartwood is moderately resistant to impregnation by preservatives; the sapwood is permeable.
Evergreen, small to medium-sized tree up to 27 m tall; bole up to 60 cm in diameter, often sinuous and slightly fluted at base; bark surface grey to brown, fissured and scaly, inner bark yellowish brown, rapidly darkening on exposure; young branches quadrangular, shortly hairy, glabrescent. Leaves opposite, digitately compound with 3–5 leaflets; stipules absent; petiole 3–6 cm long, slender; petiolules slender; leaflets obovate to oblanceolate, 9–12 cm × 1.5–3 cm, shortly acuminate at apex, toothed in upper part, papery, glabrous but glandular dotted. Inflorescence an axillary, lax cyme, few-flowered; peduncle up to 20 cm long, slender. Flowers bisexual, zygomorphic, 5-merous; calyx c. 2 mm long, with short teeth, enlarging in fruit, finely hairy; corolla white with pale purple limb, 6–7 mm long, finely hairy; stamens 4, inserted in the corolla tube, 2 long and 2 short; ovary superior, 4-celled, glabrous. Fruit an ellipsoid drupe c. 1.5 cm long, purplish black, fleshy, with woody, 4-celled stone, up to 4-seeded. Seeds without endosperm. Seedling with epigeal germination; hypocotyl 3–4 cm long, epicotyl 4–8 mm long; cotyledons leafy, shortly stalked; first pairs of leaves simple.
In Côte d’Ivoire Vitex micrantha trees flower from February to April and fruits mature in July.
Vitex comprises about 150 species and is pantropical with few species in temperate regions. In tropical Africa approximately 60 species can be found.
Vitex oxycuspis Baker occurs from Sierra Leone to southern Nigeria, and possibly also in Cameroon, DR Congo and Angola. It resembles Vitex micrantha, but generally has larger leaves and glabrous flowers. The wood of Vitex oxycuspis is used for house construction in Liberia. It is similar to the wood of Vitex micrantha, but the density is slightly higher (about 580 kg/m³ at 12% moisture content). The wood of Vitex phaeotricha Mildbr. ex W.Piep. (synonym: Vitex rufa A.Chev. ex Hutch. & Dalziel), which occurs from Sierra Leone to Côte d’Ivoire and from Cameroon to Gabon, is also similar to that of Vitex micrantha. It is used for local house construction, and additionally for tools, bowls and drums. The leaves and bark of Vitex phaeotricha, which is characterized by its densely rusty brown hairy, obtuse or shortly acuminate and entire leaflets, are applied as an antiseptic to ulcers. The fruits of Vitex oxycuspis and Vitex phaeotricha are edible but apparently not popular.
Vitex micrantha is often an understorey tree of lowland evergreen forest. It is locally common. In Ghana it is strongly associated with base-poor soils.
The 1000-seed weight is about 500 g. Germination may start up to 5 months after sowing. The germination rate is often low. In Sierra Leone Vitex micrantha has been considered a weed in production forest, and trees have been killed with arsenite.
Genetic resources and breeding
Vitex micrantha is fairly widespread and locally common and consequently not threatened by genetic erosion. However, the ongoing reduction and cutting up of the evergreen forest area in West Africa may endanger the species in the future.
Too little is known on ecology, growth rates and natural regeneration of Vitex micrantha to judge its prospects as a timber tree in sustainably managed forest. However, the often poor shape and small size of the bole seem to limit its possibilities for commercial exploitation.
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Correct citation of this article:
Lemmens, R.H.M.J., 2008. Vitex micrantha Gürke. In: Louppe, D., Oteng-Amoako, A.A. & Brink, M. (Editors). Prota 7(1): Timbers/Bois d’œuvre 1. [CD-Rom]. PROTA, Wageningen, Netherlands.