Prota 7(1): Timbers/Bois d’œuvre 1
Bot. Jahrb. Syst. 18: 165 (1893).
Verbenaceae (APG: Lamiaceae)
Premna zenkeri Gürke (1903).
Origin and geographic distribution
Premna angolensis is widely distributed in tropical Africa, from Senegal to Ethiopia, Kenya, Tanzania and Angola.
The wood of Premna angolensis (trade name: muhorro) is suitable for construction, flooring, mine props, ship and boat building, furniture and cabinet work, interior trim, toys and novelties, agricultural implements, boxes and crates, carvings, turnery, draining boards, food containers, veneer and plywood. In Kenya it is used for carving and beehives, and it has been used in construction work in mines. In Tanzania it is used for animal traps, tool handles, and as firewood.
In Côte d’Ivoire the bark of Premna angolensis is used in enemas and baths to treat fever in children. In São Tomé et Principe the bark is a remedy for malaria and fevers. In Gabon the bark is used in enemas and in fumigations against madness. In DR Congo juice squeezed from the crushed bark is instilled in the nostrils to treat epilepsy. In Tanzania a preparation of the bark is taken to treat stomach pain, and sap exuded from the bark is taken against dysentery.
In Gabon Premna angolensis is taboo for some people, and its use in the kitchen is not allowed. The bad smell of leaves and twigs thrown on a fire is believed to keep away bad spirits.
The heartwood of Premna angolensis is pale yellow-brown, the sapwood is only slightly paler. The grain is usually straight, but sometimes interlocked, texture medium and even. The smell has been described by some as sweet, by others as unpleasant. The density of the wood is 730–800 kg/m³ at 12% moisture content. Logs are usually hollow or have rotten cores. The wood seasons well, with little distortion, but some checking may occur. The wood works and planes well. It is recorded to be suitable for peeling and slicing, holds nails well, glues satisfactorily, and paints, polishes and varnishes well. The steam-bending properties are moderate to poor. The wood is durable, due to the presence of oil. The sapwood is not susceptible to Lyctus borer attack.
Small to medium-sized tree up to 21(–33) m tall, less often shrubby; bole up to 120 cm in diameter, often crooked, sometimes fluted, usually hollow; outer bark pale grey or reddish grey, finely furrowed; crown spreading, with more or less horizontal branches; branchlets sparsely pubescent and glandular, becoming glabrous. Leaves mostly in whorls of 4, less often opposite, simple and entire; petiole 3–10 cm long; blade ovate, oblong or elliptical, 4–21 cm × 3–13(–17) cm, base cuneate or rounded to slightly cordate, apex acuminate, glabrous above, pubescent beneath on main veins, glandular punctate. Inflorescence a large thyrsoid panicle, terminal or axillary, 5–30 cm long, the main branches in whorls of 2–5 and 3–9 cm long; bracts linear to lanceolate, up to 1 cm long. Flowers bisexual, zygomorphic; pedicel up to 1 mm long; calyx 1.5–2 mm long, truncate or obscurely 2-lipped, pubescent or glabrous, persistent; corolla 4-lobed, white, glabrous outside, tube 2–2.5(–3) mm long, lobes c. 1 mm long; stamens 4, inserted in corolla tube, 2 longer and 2 shorter; ovary superior, 2-celled or falsely 4-celled, style subulate, shortly 2-lobed at apex. Fruit a globose drupe 4–6 mm in diameter, apex acute, green turning purple; endocarp bony, few-seeded. Seeds oblong.
Premna comprises about 225 species, distributed mainly in the Old World tropics and subtropics. Various other Premna spp. are local sources of timber in tropical Africa. The wood of Premna hildebrandtii Gürke, distributed in Kenya and Tanzania, is hard and used for building poles, tool handles and as firewood. The foliage is browsed by goats, and a decoction of the root is used as a medicine for stomachache. The wood of Premna mooiensis (Pearson) Pieper, distributed in Mozambique and South Africa, is durable in the ground and has been used for fencing poles. The wood of Premna schliebenii Werderm., distributed in Tanzania and Mozambique, is tough and hard, and is used for building poles, tool handles and as firewood; it is unclear, however, whether this should be considered a separate species or be included in Premna chrysoclada (Boj.) Gürke. Premna schliebenii is classified as vulnerable on the IUCN Red list of threatened species.
In Kenya Premna angolensis flowers in April–May.
Premna angolensis occurs up to 2100 m altitude, in forest, bushland and grassland. In forest it occurs mainly in margins and clearings.
Genetic resources and breeding
In view of its wide distribution Premna angolensis is not threatened with genetic erosion.
Premna angolensis is a useful local source of wood for various purposes, including construction. Commercially the wood has little potential, because logs are often hollow; so its importance is unlikely to increase.
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Correct citation of this article:
Brink, M., 2007. Premna angolensis Gürke. In: Louppe, D., Oteng-Amoako, A.A. & Brink, M. (Editors). Prota 7(1): Timbers/Bois d’œuvre 1. [CD-Rom]. PROTA, Wageningen, Netherlands.
wood in transversal section
wood in tangential section
wood in radial section
detail wood in radial section
transverse surface of wood