Alstonia congensis

and A. boonei

Alstonia

Family: Apocynaceae

Other Common Names: Mujwa, Mujua (Uganda), Emien (Ivory Coast), Sindru (Ghana), Ahun, Awun (Nigeria), Bokuk, Kanja (Cameroon), Kaiwi, Kauwi (Sierra Leone).

Distribution: Widely distributed throughout West and Central Africa; abundant in humid forests of the Cameroons.

The Tree: Reaches a height of 130 ft, boles usually cylindrical and clear to 80 ft; trunk diameters 2 to 4 ft over a deeply fluted and buttressed base.

The Wood:

General Characteristics: Wood yellowish white with no distinction between sapwood and heartwood. Texture fine to medium; grain usually straight; luster low; without characteristic odor or taste. Large slitlike radial canals often occur at intervals of 1 to 3 ft.

Weight: Basic specific gravity (ovendry weight/green volume) 0.33; air-dry density 25 pcf.

Mechanical Properties: (2-cm standard)

Moisture content Bending strength Modulus of elasticity Maximum crushing strength

(%) (Psi) (1,000 psi) (Psi)

Green (40) 5,220 930 2,920

12% 8,560 1,200 5,240

12% (44) 7,000 840 3,920

Janka side hardness 370 lb for green and 410 lb for dry material. Amsler toughness 50 in.-lb at 12% moisture content (2-cm specimen).

Drying and Shrinkage: Seasons rapidly with little or no degrade due to warping and checking. Kiln schedule T10-D4S is suggested for 4/4 stock and T8-D3S for 8/4. Shrinkage green to ovendry: radial 4.0%; tangential 5.4%; volumetric 12.4%. Movement in service is rated as small.

Working Properties: Works easily with both hand and machine tools and dresses to a smooth finish if sharp cutting edges are used. Glues and nails well; steam- bending properties are poor.

Durability: Wood is highly perishable and should be converted rapidly or given a chemical dip to prevent stain; liable to termite attack as well as powder-post beetle attack.

Preservation: Easily treated, absorptions over 30 pcf of preservative oils are reported using either open tank or pressure systems.

Uses: Light construction, plywood core stock, boxes and crates, joinery, furniture components.

Additional Reading: (3), (16), (40), (44)