Khaya (African Mahogany)

The following information is posted with permission of Timber Research and Development Association (TRADA) and is taken from their red booklets Timbers of the World. © TRADA

Khaya spp. Family: Meliaceae

The name African Mahogany covers all species of Khaya, although their timbers vary somewhat in character, particularly in weight. The bulk of the timber shipped is produced by K. ivorensis and K. anthotheca each with moderately light-weight, pale to medium-red wood, and it is timber of this type which is accepted commercially as African mahogany; East African K. nyasica is generally similar. A small proportion of K. grandifoliola is moderately light in weight but much of its timber and that of K. senegalensis is darker and appreciably heavier than that normally accepted as African mahogany. It has been suggested that such heavy wood should be marketed separately, and the name heavy African mahogany is recommended.

Other names

Khaya ivorensis A. Chev. (West Africa).
Khaya anthotheca (WeIw) A.DC. (West and East Africa). Ghana, Ivory Coast, Takoradi. Grand Bassam mahogany, according to origin (UK); acajou d Afrique (France); khaya (USA).

K. ivorensis is also known as Benin, Lagos, Nigerian, and Degema mahogany, Lagoswood and ogwango (Nigeria), and ngollon (Cameroons).

K. anthotheca is also known as krala (Ivory Coast): mangona (Cameroons): munyama (Uganda).

Khaya nyasica Stapf. ex Baker f. (East Africa).
Mozambique mahogany, mbaua, umbaua (Mozambique); mbawa (Malawi); mkangazi (Tanzania).

Khaya grandifoliola C.DC. (West Africa). Beninwood, Benin mahogany (Nigeria); grandifoliola (UK).

Khaya senegalensis (Desr.) A. Juss. (West and Central Africa) dry-zone mahogany (General); bissilom (Port Guinea); Guinea mahogany (UK).

Weight when dried (kg/rn3)

K. ivorensis 530
K. anthotheca 540
K. nyasica 590
K. grandifoliola 720*
K. senegalensis 800

*Occasional pieces of light-weight K. grandifoliola are included with species designated as African mahogany.

Distribution

The trees

K. ivorensis. Grows to a height of 30m or more with a clear bole 12m to 25m in length above the buttresses, and with a diameter of 1 .0m upwards to 2.0m or more. The habit of all Khaya species varies considerably with the growth conditions, but the banks of rivers and streams appear to suit the requirements of the species better than drier soils. Thus K. anthotheca is usually not such a good shape as K. ivorensis, and K. grandifoliola is not so tall, and generally has a more crooked growth habit, though it usually attains a larger girth than other species.

K. senegalensis is a smaller tree and not so well shaped as the usual types of commercial mahogany. It grows mainly in the deciduous savannah forests and generally reaches a height of 15m to 24m with a diameter of about 1.0m.

The timber

African mahogany, ie. K. ivorensis. K. anthotheca. and K. grandifoliola (in part).

The heartwood is distinctly pink when freshly sawn, but when seasoned varies in colour from light pinkish-brown to a deep reddish shade; the yellowish-brown sapwood is not always clearly demarcated. The heartwood of K. grandifoliola tends to be darker.

The grain is usually interlocked and the texture is of a coarser nature than that of American mahogany. The quality varies wit the locality of growth; some localities are said to produce coarse-textured logs with spongy hearts while others are noted for the fine texture and character of their timber. A common feature is the defect known as 'thunder shake (cross fractures), which are particularly abundant in trees with a soft or 'punky heart.

K. nyasica from East Africa inclines to a reddish or golden-brown-shade.

Heavy mahogany (dry-zone mahogany), ie K. senegalensis and K. grandifoliola (in part).

The timber of both these species is appreciably denser, and typically darker than ordinary commercial African mahogany, K senegalensis in particular being deep red-brown with a purple tinge. In respect of grain and texture, there is little difference from the characteristics of African mahogany, but K. grandifoliola is reputed to be of high quality.

Drying

African mahogany dries fairly rapidly with generally little degrade. Care should be taken to prevent distortion and splitting. and this aspect is of greater importance when drying heavy mahogany.

Durability

All Khaya species are considered moderately durable.

Strength

The strength of African mahogany compares favourably with that of American mahogany (Swietenia), but is more resistant to splitting. No data are available regarding strength of heavy mahogany although it can be assumed the heavier species are stronger than African mahogany.

Working qualities

The lighter material is easy to work but the heavier species are slightly more difficult. They all have a tendency to pick up on quarter-sawn surfaces, due to interlocking grain, and a reduction of cutting angles to 15^o helps to overcome this tendency. All species can be glued satisfactorily, and generally have good nailing and screwing properties. Takes a high polish and a good finish.

Uses

African mahogany is an important timber for furniture, indoor decoration, both in the solid and as veneer, high quality joinery for staircases, panelling, and domestic flooring, boat planking and cabins, banisters and handrails.

Heavy mahogany has similar uses; K. senegalensis is said to provide the best surface-finishing of all the African mahoganies and is a popular timber in East Africa for lorry bodies, construction work, and decking in boats apart from the normal uses of furniture etc.