Common Name: Okoumé

General Information

Okoumé is an evergreen tree usually growing 35 - 40 metres tall but with trees up to 60 metres reported. The cylindrical bole is often distorted and bent, it can be unbranched for up to 21 metres and up to 2 metres in diameter with buttresses up to 3 metres high[, ].
This species is the most important timber tree in Gabon, from where it is exported in quantity. Usually gathered from the wild, some plantations have been established, mainly within the plants native range[]. The gum resin is also sometimes exported[].
The tree occurs abundantly in an area covering west and central Gabon, and also in small areas of neighbouring countries. Repeated felling has led to the deterioration of the gene pool in certain areas, and there is some concern as to the long-term status of the species. The plant is classified as 'Vulnerable' in the IUCN Red List of Threatened Species(2011)[].

Known Hazards

None known

Botanical References

Range

West tropical Africa - Cameroon, Gabon, Congo.

Habitat

Closed forest with Aucoumea, Lophira alata, Sacoglottis gabonensis; cultivations; clearings; open ground; road sides; edges of savannahs; at elevations from sea level to around 600 metres, occasionally to 1,400 metres[, ].

Properties

Conservation Status	Vulnerable
Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	35.00 m
Growth Rate	Fast
Pollinators	Bees, Flies
Self-fertile	No
Cultivation Status	Cultivated, Wild

Cultivation Details

Okoumé is a plant of the moist tropics, where it is found at elevations up to 1,400 metres. It grows best in areas where the mean annual temperature is within the range 23 - 26°c, with a mean maximum temperatures of the hottest month 32 - 36°c, and mean minimum temperature in the coldest month 10 - 15°c[]. It requires a mean annual rainfall in the range 1,200 - 3,000mm, and a marked dry season (less than 50 mm/month) of around 3 - 4 months[].
Requires a sunny position, though young plants can survive for some years in shady positions[]. Succeeds on a wide range of acid soils (such as ferralitic arenosols, ferralitic soils, podzoluvisols) developed on various substrates. It can grow on infertile sandy soils but prefers fertile, deep sandyclayloams. It can tolerate a certain degree of impeded drainage, but not long periods of waterlogging[].
A relatively fast growing tree, faster even than Guarea cedrata[]. Trees reach an average height of about 10 metres in their first 4 years; from the age of 10 to 50 years, the growth rate of dominant trees is about 1 metre per year, and eventually they can reach a height of about 50 metres. Suppressed trees grow very slowly, only reaching about 15 metres in 50 years[].
Growth in bole diameter is variable and depends on age, stand density, site fertility, hierarchical position of the tree and thinning rates. In coastal Gabon, bole diameters of 30 - 80cm after 50 - 60 years for dominant trees and 10 - 40cm for suppressed trees have been recorded[].
A shallow-rooted species, with virtually no taproot[]. When around 6 - 12 years old, populations become organized into 'biological cells' through joining root grafts. When 10 - 25 years old, natural and planted populations segregate into dominant and suppressed trees[].
Trees start to flower when they are about 10 years old, but fruiting only begins after 15 years[].
A dioecious species, both male and female forms need to be grown if fruit and seed are required[].

Edible Uses

None known

Medicinal

A gum-resin obtained from the bark is used for treating superficial wounds and abscesses[, ].

The bark is considered astringent and is used in the treatment of diarrhoea[, ]. Scrapings of the bark, combined with the seed of maleguetta pepper and the leaves of a bitter Solanum species, are taken by girls at the commencement of puberty[].

Several terpenoids are present in the bark resin, including α-terpineol and β-phellandrene and several tetracyclic and pentacyclic triterpenes[].

Agroforestry Uses:

Okoumé is a long-lived pioneer of, in particular, large forest clearings and fire-protected savannah edges, where it often becomes mono-dominant. A fast-growing species, it could be used as a pioneer when establishing woodland[]

Other Uses

The bark contains a gum-resin that smells of turpentine. It is used in torches and lamps, for incense, and also for cosmetic applications in skin care products and nail polish[, ].
The resin is used to disinfect water[].

The heartwood is salmon pink to pale pinkish brown or reddish brown, darkening upon exposure to light to a mahogany-like colour; it is distinctly or indistinctly demarcated from the white to pale grey sapwood. The grain is usually slightly interlocked; texture medium to moderately fine; quarter-sawn surfaces with a striped or mottled figure; growth rings distinct due to alternating paler and darker layers. A lightweight hardwood, it is comparatively soft; has little natural resistance to decay; and is susceptible to termites, marine borers and fungal attack. It is easy to work with both hand- and machine tools, but worked surfaces tend to be woolly, so cutting edges must be kept sharp. It contains up to 0.3% silica and sawing requires tungsten-carbide-tipped cutters as saw teeth blunt rather quickly. When planing, an angle of 20° is necessary to prevent tearing. The wood responds well to sanding, can be nailed without pre-boring, and glues and stains well. It can be polished to a lustrous surface. The wood is often rotary-cut for the production of plywood; figured wood is sliced into highly decorative veneers for panelling and cabinet making[]. This is one of the best timber species for making plywood. It is also made into blockboard, particle board and veneer, and is widely used in boat building for decorative interior panelling and for exterior applications. The wood is also suitable for light interior construction, carpentry, furniture, sports equipment, cigar boxes and packing cases. Locally it is used for making canoes[, ].
The wood is resinous, making it somewhat inflammable and is often used as a fuel[].

Propagation

Seed - does not require pre-treatment and can be sown directly in individual containers (20 - 30 cm high, 10 - 15cm in diameter) filled with a mixture of sand and clay. Two seeds are placed per bag; the best seedling is selected after 3 - 4 weeks. After 10 weeks the seedlings can be 20 - 25cm tall, have 5 - 7 simple leaves and are ready for transplanting[].
Seeds lose viability within 1 month in the field, but can be stored at 4°c in airtight containers for up to 3 years after being dried to 8% moisture content[].
Propagation by grafting and cuttings is possible[].

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