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(English) : African walnut
Coula edulis is an evergreen, medium-size to large tree reaching 25 m, with a large, dense crown casting a deep shade. Form of the bole is generally short, bossed, branched low down, and sometimes slightly swollen at the base, not usually exceeding 6 m in length and 0.8 m in diameter. Bark thin, rather smooth, lenticillate, greenish-brown, slightly fissured; slash sepia or yellow; in young trees whitish and resinous. Leaves alternate, simple, exstipulate, oblong or elliptic, coriaceous, 10-30 x 4 cm. Secondary nerves impressed on the upper surface and prominent on the lower surface. Young shoots and leaves covered with rust-coloured, stellate hairs. Flowers small, in short axillary racemes and covered with rusty tomentum. They are tetramerous or pentamerous, with rather thick, glabrous, greenish-yellow petals. Fruit an ellipsoidal drupe, 3-4 cm long, with an extremely hard kernel. Flesh surrounding the kernel green or reddish, 5-6 mm thick and smooth. The specific name, ‘edulis’, means edible.
Ecology and distributionHistory of cultivation
Native of western tropical Africa.
C. edulis has its main distribution in the rain forest. It tolerates moderate shade and is normally a constituent of the upper reaches of the lower storey but is also found in the upper canopy. It is semi-gregarious and does not appear to be selective about sites.
Native : Democratic Republic of Congo, Nigeria, Sierra Leone
Biophysical limitsSoil type: The tree has no special soil requirements.
The tree is evergreen. Flowering takes place from April to June and the fruit is available from August to January. Fruit is usually found under the mother trees.
Propagation and managementPropagation methodsFruit is borne plentifully, and broken shells can be seen under the trees in the fruiting season. Because of the hard integument, germination is rather poor and may take up to a year.
C. edulis can be used as a plantation tree with a final spacing of 10 x 12 m. Shading is beneficial when plants are young.
Functional usesProductsFood: The oily kernel has a taste comparable to that of a chestnut or hazelnut. It can be eaten raw, grilled or boiled. It contains 50% fat, of which 87% is oleic acid. Fuel: Wood produces suitable charcoal. Timber: The sapwood is pinkish-brown, the heartwood is dark red or violet brownish-red. It is extremely hard, heavy, close-grained, and resists water well. It is also resistant to insect attack, particularly termites. It has the disadvantage of being liable to shake and crack. It is used for making piles for bridges and railway ties.
Pests and diseasesC. edulis is very resistant to marine borers.
BibliographyFAO. 1982. Fruit-bearing forest trees: technical notes. FAO-Forestry-Paper. No. 34. 177 pp.
Savill PS and Fox JED. 1967. Trees of Sierra Leone.
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