Prota 7(2): Timbers/Bois d’œuvre 2
Engl., Pflanzenw. Ost-Afrikas C: 301 (1895).
Afrocrania volkensii (Harms) Hutch. (1942).
Afrocrania (En). Mnyandege (Sw).
Origin and geographic distribution
Cornus volkensii occurs in mountain regions from DR Congo and southern Sudan east to Kenya and south to Zimbabwe and Mozambique.
The wood, known as ‘mukorombosi’ in Kenya, is used for utensils and handles of implements. It is suitable for light construction, light flooring, joinery, interior trim, ship building, furniture, cabinet work, toys, novelties, boxes, crates, turnery, veneer and plywood. It is also used as firewood. In Tanzania the leaves are applied as a poultice to boils. Cornus volkensii is planted in reforestation programmes and as roadside tree.
The heartwood is yellowish white to pale reddish brown, occasionally with greyish streaks, indistinctly demarcated from the narrow sapwood. The grain is straight, texture medium, even. The wood is medium-weight, with a density of about 610 kg/m³ at 12% moisture content. It air dries without much degrade, but slowly. The rates of shrinkage are moderate. It saws and works well with both hand and machine tools. The nailing, screwing and gluing properties are satisfactory. The wood is not durable and susceptible to attacks by blue stain fungi, termites, Lyctus borers and marine borers.
Evergreen, dioecious, small to medium-sized tree up to 20(–30) m tall; bole usually straight and cylindrical, up to 100 cm in diameter; bark surface rough, grey, with large lenticels, inner bark granular; crown with spreading branches; twigs initially short-hairy, becoming glabrous. Leaves opposite, simple and entire; stipules absent; petiole up to 2 cm long, grooved above; blade elliptical to ovate or lanceolate, 3.5–17.5 cm × 1.5–7 cm, cuneate at base, acuminate at apex, finely appressed-hairy when young but becoming glabrous, pale green, pinnately veined with 3–4 pairs of prominent, curving and ascending lateral veins. Inflorescence a terminal false umbel, up to 100-flowered, very young inflorescence enclosed by an involucre of 4 ovate to orbicular bracts, 7–8 mm × 6–7 mm, soon falling; peduncle 2.5–5 cm long, thickened at apex, silvery hairy. Flowers unisexual, regular, 4-merous; pedicel up to 12 mm long; sepals minute; petals free, 2–3 mm long, sparsely hairy, creamy white to greenish yellow; stamens free, alternating with petals, c. 1.5 mm long; ovary inferior, cylindrical, 2-celled, style short and thick, lower part surrounded by disk, stigma club-shaped or slightly 2-lobed; male flowers with rudimentary style, female flowers with rudimentary stamens. Fruit an ellipsoid drupe 1–1.5 cm long, minutely hairy, red turning purplish black when fully ripe, crowned by the remains of calyx, disk and style, 2-seeded.
Cornus comprises about 60 species, most of them occurring in temperate regions of the Northern Hemisphere. Cornus volkensii is the only Cornus species of tropical Africa and the only species which is dioecious and has spiny pollen; it has often been considered to represent a distinct genus, i.e. Afrocrania. However, phylogenetic and biogeographic reconstruction of the evolutionary history based on DNA data as well as extant and fossil morphology showed that Cornus volkensii represents an old lineage of a group of Cornus species from Eurasia and South America. It was postulated that the group arose in Europe and distributed from there to Africa by the middle of the Eocene, about 45 million years ago.
Cornus volkensii occurs in mountain forest at (1200–)1800–3000 m altitude, often along streams. It may dominate the canopy layer of the forest. In Kenya it often occurs together with East African camphor wood (Ocotea usambarensis Engl.) and in Uganda with real yellowwood (Podocarpus latifolius (Thunb.) R.Br. ex Mirb.). In mountains of Tanzania, large areas of forest composed almost entirely of Cornus volkensii and Ficalhoa laurifolia Hiern are found, and in Zimbabwe Cornus volkensii locally co-dominates with Ilex mitis (L.) Radlk. and Olea capensis L. It is often associated with bamboo species.
Cornus volkensii may regenerate in intensively grazed areas.
Genetic resources and breeding
Cornus volkensii is widespread and in several regions abundant, and does not seem to be threatened.
Cornus volkensii is an interesting species for planting in agroforestry programmes in high-altitude regions of tropical Africa. Research is needed on growth rates and methods of propagation.
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Correct citation of this article:
Lemmens, R.H.M.J., 2010. Cornus volkensii Harms. In: Lemmens, R.H.M.J., Louppe, D. & Oteng-Amoako, A.A. (Editors). Prota 7(2): Timbers/Bois d’œuvre 2. [CD-Rom]. PROTA, Wageningen, Netherlands.