Common Name: African Walnut

General Information

African walnut is a large, evergreen tree with a dark, heavy crown; it can grow up to 45 metres tall. The bole, which is usually straight and cylindrical but can be sinuous, can be branchless for up to 25 metres and up to 120cm, occasionally 200cm in diameter[, ].
The tree is commonly harvested from the wild for local use as a medicine and source of wood. The wood is a valuable timber that is often traded. It is occasionally planted as a roadside tree[].

Known Hazards

The sawdust may be irritant[].

Botanical References

Range

Western tropical Africa - Sierra Leone to Zaire, south to Angola.

Habitat

A canopy and emergent tree, scattered in evergreen forest and semi-deciduous forest at elevations up to 1,200 metres[, ].

Properties

Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	35.00 m
Cultivation Status	Ornamental, Wild

Cultivation Details

A plant of the moist tropics, where it is found at elevations up to 1,200 metres. It grows in areas where the mean annual rainfall is in the range 1,000 - 2,800mm and the mean annual temperature ranges from 20 - 29°c[, ].
Prefers a moist but free draining locality on alluvial soils[]. Often found on acid soils in the wild[]. Young trees grow best if they are given some shade, though older trees prefer sunnier conditions[].
Early growth is generally slow, with planted seedlings reaching 100 cm height in 2 years and 150 cm in 3 years[]. In exceptional cases trees can reach a height of 2.5 metres after 1 year[].
After the first few years, growth becomes faster, and there are records of young trees attaining 9 metres in height after 7 years[].
In plantations in Uganda an average bole diameter of 25cm was reached after 25 years, whereas in Nigeria and Cameroon a mean annual diameter increment of 10 - 18mm was recorded[].
In experiments in Gabon, 11-year-old trees planted in light shadow were 20 metres tall and 16.5 cm in diameter, whereas growth of trees planted in full sun was slower[]. In natural forest the mean annual diameter increment is about 5 mm[].
Natural regeneration is often abundant, although the seed suffers heavy predation. Seedlings of about 20 cm tall may be abundant even in full shade, where they may survive for several years, but saplings only grow where gaps develop in the forest canopy[].

Edible Uses

None known

Medicinal

The pulped bark is rubbed on the chest to treat pulmonary troubles[]. The bark is also used against dental caries[].

Agroforestry Uses:

It is promoted in Uganda for tree planting programmes; it is locally planted as a shade tree in agroforestry programmes, for crops such as coffee and banana[].

Other Uses

The heartwood is yellowish brown to greyish brown, often with golden and blackish markings; it is distinctly demarcated from the 3 - 7cm wide band of pale brown to pale grey sapwood. The grain is usually interlocked; the texture moderately fine to fine. The wood is lustrous and has an attractive appearance, with a ribbon-like aspect on quarter-sawn surfaces and a cedar-like scent. It is light in weight; soft; somewhat durable, being resistant to dry wood borers, somewhat resistant to fungi and susceptible to termites. It seasons fairly quickly with only a slight risk of checking and distortion; once dry it is stable in service. The wood is easy to saw and work with ordinary tools; there is some tendency of picking up of grain when the wood is quarter-sawn, and planing may be difficult because of the presence of interlocked grain, resulting in tearing; it finishes well, but for a fine polish the use of a filler is recommended; nailing and screwing properties are good, although there may be some tendency to splitting; gluing, painting and varnishing properties are satisfactory; the steam bending properties are moderate. The wood is highly valued for high class furniture, cabinet work, flooring, carpentry, joinery, interior trim, stairways, panelling and decorative veneer and plywood[]. It is locally used for house construction, vehicle bodies, implements and handles, and to make canoes[]. It is suitable for ship building, sporting goods, toys, novelties, railway sleepers, carving, boxes, crates, turnery and pulpwood[, ].
The wood is also used as firewood and for charcoal production[].

Propagation

Seed - best sown as soon as it is ripe since it has a short viability[]. Seeds start germinating after 8 - 16 days, with up to 90% germination rate for fresh seed, but only about 30% for 2 month old seed[].
A successful method of propagation by stem cuttings has been developed in Cameroon. Long, thin cuttings with large leaf areas (50 - 200 cm²) made from apical nodes of multi-stemmed stock-plants rooted best, with a rooting rate of up to 60%[]
Stem cuttings root best in coarse gravel[].

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