Uapaca thouarsii (PROTA)

Plant Resources of Tropical Africa Introduction

List of species

General importance
Geographic coverage Africa
Geographic coverage World

Uapaca thouarsii Baill.

Protologue: Etude Euphorb.: 596 (1858).

Family: Euphorbiaceae (APG: Phyllanthaceae)

Origin and geographic distribution

Uapaca thouarsii is endemic to Madagascar, where it occurs throughout the eastern parts of the island.

Uses

The wood, known as ‘voapaka’ together with the wood of several other Uapaca spp., is used for construction of houses and bridges, railway sleepers and shingles. It is suitable for mine props, ship building (ribs) and vehicle bodies, but less suitable for flooring, joinery and furniture because the wood is not very stable in service. It is also used as firewood and for charcoal production.

The fruits are edible. Bark decoctions are taken to treat colic.

Properties

The heartwood is reddish brown to dark brown and not distinctly demarcated from the slightly paler, wide sapwood. The grain is usually straight, texture moderately coarse. The wood is lustrous. Quarter-sawn surfaces show a nice silver grain figure.

The wood is fairly heavy, with a density of 750–900 kg/m³ at 12% moisture content. It should be air dried with care to prevent distortion and warping. Quarter-cutting before drying is recommended. The rates of shrinkage are quite high, from green to oven dry 3.9–6.2% radial and 10.5–12.8% tangential. It takes 2–3 months to air dry boards of 2.5 cm thick from green to 30% moisture content. Once dry, the wood is moderately stable in service.

At 12% moisture content, the modulus of rupture is 135–182 N/mm², modulus of elasticity 9800–15,420 N/mm², compression parallel to grain 50–73 N/mm², shear 11 N/mm², cleavage 21 N/mm and Chalais-Meudon side hardness 3.4–6.3.

The wood is rather difficult to saw and work; it contains silica and has a blunting effect on tools. It is recommended to use stellite-tipped saw teeth and tungsten-carbide tipped cutting edges. The wood planes to rather rough surfaces due to the fibrous tissues. It nails and glues moderately well, and varnishes well. It is not suitable for veneer. The heartwood is moderately durable, being quite resistant to fungi and dry-wood borers, and moderately resistant to termites and marine borers. The heartwood is resistant to impregnation with preservatives.

Description

Evergreen, dioecious, small to medium-sized tree up to 20(–25) m tall; bole up to 60 cm in diameter, usually on stilt roots; bark surface slightly rough, greyish white; crown elongate, much-branched; twigs waxy-viscous and greyish short-hairy when young, soon becoming glabrous, with conspicuous leaf scars. Leaves arranged spirally, crowded towards the end of the branches, simple and entire; stipules absent; petiole 2–4 cm long, jointed near apex; blade obovate, 10–14 cm × 4–9 cm, base cuneate, apex obtuse to rounded, thin-leathery, glabrous, pinnately veined with 5–7 pairs of lateral veins. Male inflorescence an axillary globose head c. 8 mm in diameter, on 2–4 cm long peduncle, with up to 7 bracts up to 12 mm long; female flowers solitary. Flowers unisexual, 4–5-merous; male flowers sessile, with unequal calyx lobes, stamens free, rudimentary ovary shorter than stamens, glabrous; female flowers with unequal and hairy calyx lobes, ovary superior, 3-celled, styles 3, branched at apex. Fruit an ovoid-globose drupe up to 3 cm long, warty, yellowish to brownish, with (1–)2–3 stones; stones 3-angled, slightly flattened, 1–1.5 cm long, 1-seeded.

Other botanical information

Trees grow fairly fast. Young trees of 7 years old reached an average height of 4 m. They tolerate shade fairly well. Trees flower in November–January and ripe fruits can be found in November–December; fruits take a long time to mature, about one year.

Uapaca comprises about 50 species from tropical Africa and Madagascar, and is in need of a complete revision. About 12 species can be found in Madagascar, all endemic. Some of these provide useful timber, but for most species the edible fruits are more important.

Uapaca betamponensis

Uapaca betamponensis Leandri is a small tree up to 15 m tall with a slender bole branchless for up to 12 m, only known from forest north of Toamasina in eastern Madagascar. Its reddish brown wood has been used for planks and for charcoal production, and the fruits are edible.

Uapaca densifolia

Uapaca densifolia Baker is a small to medium-sized tree up to 20 m tall, widely distributed in central and eastern Madagascar. Its wood is useful for house and bridge construction and for railway sleepers. The wood is medium-weight with a density of about 750 kg/m³ at 12% moisture content, and other wood properties are quite similar to those of Uapaca thouarsii. It is also used for charcoal production. The fruits are edible.

Uapaca louvelii

Uapaca louvelii Denis is a small tree up to 15 m tall, widely distributed in eastern Madagascar. Its wood is useful for house and bridge construction and for railway sleepers, but impregnation with preservatives may be needed for these purposes because it is often only moderately durable. The wood is fairly heavy with a density of about 815 kg/m³ at 12% moisture content, and other wood properties are quite similar to those of Uapaca thouarsii, although the wood is slightly harder. It is also used for charcoal production. The fruits are edible.

Ecology

Uapaca thouarsii occurs in humid evergreen forest, up to 900 m altitude, in regions with an average annual rainfall of 1500–3000(–3500) mm and up to 2 dry months, and a mean temperature of 20–24°C. It prefers sandy or loamy-sandy soils.

Management

The 1000-seed weight is about 600 g. Seeds can be stored in a cool locality for up to 5 months without losing much germination capacity. The germination rate is 60–80%. Pre-treatment of seeds is not needed before sowing. The seeds are usually sown in plastic bags. Propagation by suckers is sometimes possible. Care should be taken in harvesting because the boles of older trees often have heart rot.

Genetic resources

There are no signs that Uapaca thouarsii is threatened by genetic erosion at present, although the high pressure on natural forest in eastern Madagascar may become a serious threat even for such a widespread species.

Prospects

The wood is mainly used locally and this situation will probably not change because the stilt roots and difficulties in processing the timber limit the possibilities for export. Uapaca thouarsii can be useful for enrichment planting in natural forest.

Major references

• Blaser, J., Rajoelison, G., Tsiza, G., Rajemison, M., Rabevohitra, R., Randrianjafy, H., Razafindrianilana, N., Rakotovao, G. & Comtet, S., 1993. Choix des essences pour la sylviculture à Madagascar. Akon’ny Ala: Bulletin du Département des Eaux et Forêts 12–13. 166 pp.

• 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.

• Parant, B., Chichignoud, M. & Rakotovao, G., 1985. Présentation graphique des caractères technologiques des principaux bois tropicaux. Tome 5. Bois de Madagascar. CIRAD, Montpellier, France et Département des Recherches forestières et piscicoles du FOFIFA, Antananarivo, Madagascar. 161 pp.

• Sallenave, P., 1955. Propriétés physiques et mécaniques des bois tropicaux de l’Union française. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 129 pp.

• Sallenave, P., 1971. Propriétés physiques et mécaniques des bois tropicaux. Deuxième supplément. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 128 pp.

Other references

• Boiteau, P., Boiteau, M. & Allorge-Boiteau, L., 1999. Dictionnaire des noms malgaches de végétaux. 4 Volumes + Index des noms scientifiques avec leurs équivalents malgaches. Editions Alzieu, Grenoble, France.

• Guéneau, P., Bedel, J. & Thiel, J., 1970–1975. Bois et essences malgaches. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 150 pp.

• Leandri, J., 1958. Euphorbiacées (Euphorbiaceae). Flore de Madagascar et des Comores (plantes vasculaires), famille 111. Firmin-Didot et cie., Paris, France. 209 pp.

• Rabevohitra, R., 1984. Contribution à l’étude de la flore forestière de Madagascar : sur la germination de quelques essences forestières. Fiche Technique de germination sous N° 524-FOFIFA/DRFP, Antananarivo, Madagascar. 27 pp.

• Schatz, G.E., 2001. Generic tree flora of Madagascar. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 477 pp.

• Takahashi, A., 1978. Compilation of data on the mechanical properties of foreign woods (part 3) Africa. Shimane University, Matsue, Japan. 248 pp.

Author(s)

• R.H.M.J. Lemmens, PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article

Lemmens, R.H.M.J., 2012. Uapaca thouarsii Baill. 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 23 April 2026.

• See the Prota4U database.