Baikiaea insignis (PROTA)

Plant Resources of Tropical Africa Introduction

List of species

General importance
Geographic coverage Africa
Geographic coverage World
Cereal / pulse
Vegetable
Medicinal
Timber
Fuel
Ornamental
Auxiliary plant
Food security

distribution in Africa (wild)

1, flowering twig; 2, dehisced fruit with one valve remaining; 3, seed. Redrawn and adapted by J.M. de Vries

tree (TopTropicals)

leaves (TopTropicals)

flowers (TopTropicals)

flowers (TopTropicals)

flower (TopTropicals)

flower (TopTropicals)

fruits (TopTropicals)

wood in transverse section

wood in tangential section

wood in radial section

Baikiaea insignis Benth.

Protologue: Trans. Linn. Soc. London 24: 314 (1866).

Family: Caesalpiniaceae (Leguminosae - Caesalpinioideae)

Baikiaea insignis occurs from southern Nigeria eastward to Uganda and western Tanzania, and southward to DR Congo and northern Angola. It has been introduced in some other tropical regions as an ornamental tree, e.g. in India, Sri Lanka and the Caribbean islands.

The wood is used for construction, flooring, carpentry, furniture, shelves, tool handles and grain mortars. It is suitable for interior trim, ship building, railway sleepers, agricultural implements, carvings, veneer and plywood. The wood is also used as firewood and for charcoal production.

The leaves are occasionally eaten as a vegetable. Roasted and pounded seeds are also eaten, mainly in times of famine. Baikiaea insignis is sometimes planted as ornamental tree because of its large flowers.

The wood is used locally and usually not available on the international timber market.

The heartwood, which is rarely more than 20 cm in diameter, is dark brown and often distinctly demarcated from the very wide, pinkish brown or greyish brown sapwood, turning pale greyish brown with darker patches and streaks upon exposure. The grain is usually straight, sometimes slightly interlocked, texture medium. Gum deposits are present in the wood.

The wood is heavy, with a density of about 750–980 kg/m³ at 12% moisture content. It air dries fairly well with moderate degrade, but it is liable to borer attack during drying and therefore kiln drying is recommended. End splitting may occur and there is a tendency to distortion in thicker boards, especially if heartwood is present. The rates of shrinkage are moderate, from green to oven dry 3.5–3.8% radial and 6.4–6.7% tangential. Once dry, the wood is moderately stable in service.

At 12% moisture content, the modulus of rupture is 117 N/mm², modulus of elasticity 18,350 N/mm², compression parallel to grain 65 N/mm², shear 12 N/mm², Janka side hardness 7870 N and Janka end hardness 9340 N.

The gummy sawdust may cause overheating in sawing operations of green wood. Because of its density, the wood is difficult to rip saw; a cutting angle of 15° is recommended. The wood works fairly well with machine tools, but more difficult with hand tools. It planes well, but the presence of interlocked grain may cause picking up of grain. It moulds, drills and mortises well, but with a tendency to split at the exits. Pre-boring is needed for nailing. The wood takes paint and varnish well. It peels well after steaming at 100°C during 72 hours, but woolly zones may occur. It slices satisfactorily, producing good-quality veneer. The turning properties are good. The wood is not durable, being liable to termite and borer attacks. The sapwood is moderately resistant to impregnation with preservatives, the heartwood is resistant.

Resin may exude in small quantities from the tree; it hardens upon exposure, resembling copal from Guibourtia spp. Bark and roots contain tannin, saponins, steroids and terpenes.

• Evergreen, small to medium-sized tree up to 25(–35) m tall; bole branchless for up to 15(–20) m, up to 60(–100) cm in diameter, often fluted at base but usually without buttresses; bark surface smooth or slightly fissured, grey to greyish brown, inner bark thin, slightly fibrous, pinkish brown to red-brown; crown usually dense, with spreading branches; twigs glabrous, with numerous lenticels.
• Leaves arranged spirally, imparipinnately compound with (2–)3–8(–10) leaflets; stipules minute; petiole and rachis together up to 30 cm long; petiolules 0.5–2 cm long; leaflets usually alternate, ovate to elliptical or oblong-lanceolate, 7–40 cm × 3–17 cm, obtuse to short-acuminate at apex, with slightly recurved margins, leathery, glabrous, pinnately veined with up to 12 pairs of lateral veins.
• Inflorescence a terminal or axillary raceme up to 8.5(–12) cm long, densely brownish hairy; bracts up to 4 mm long.
• Flowers bisexual, slightly zygomorphic, large and showy, scented; pedicel 2–5 cm long; sepals 4, oblong to linear, 7–12(–15) cm long, 1 broader than other 3, densely brownish short-hairy; petals 5, free, obovate, 10–20 cm × 5–10 cm, crinkled near margins, 4 white or cream-coloured, 1 slightly narrower and pale yellow; stamens 10, 9 fused at base and 1 free, up to 18 cm long; ovary superior, 2.5–4 cm long, flattened, with stipe 2–2.5 cm long, 1-celled, style 5–9(–11) cm long.
• Fruit a flattened, woody pod 17–40(–60) cm × 5–12 cm, stiped, densely brown hairy, dehiscing with 2 spirally twisting valves, several-seeded.
• Seeds ellipsoid, 3–4.5 cm × 1.5–3 cm, flattened, dark red.
• Seedling with epigeal germination; hypocotyl 0.5–7 cm long, epicotyl 18–25 cm long, glabrous; first leaves alternate, with 2–4 leaflets.

Baikiaea comprises about 4 species and is restricted to mainland Africa. It is related to Copaifera, Detarium, Sindora and Tessmannia.

Two subspecies have been distinguished in Baikiaea insignis; subsp. minor (Oliv.) J.Léonard (synonym: Baikiaea minor Oliv.) differs from subsp. insignis in its usually smaller leaves, flowers and fruits.

Wood-anatomical description (IAWA hardwood codes):

• Growth rings: (1: growth ring boundaries distinct); (2: growth ring boundaries indistinct or absent).
• Vessels: 5: wood diffuse-porous; 13: simple perforation plates; 22: intervessel pits alternate; 23: shape of alternate pits polygonal; 25: intervessel pits small (4–7 μm); 26: intervessel pits medium (7–10 μm); 29: vestured pits; 30: vessel-ray pits with distinct borders; similar to intervessel pits in size and shape throughout the ray cell; 42: mean tangential diameter of vessel lumina 100–200 μm; 47: 5–20 vessels per square millimetre; (48: 20–40 vessels per square millimetre); 58: gums and other deposits in heartwood vessels.
• Tracheids and fibres: 61: fibres with simple to minutely bordered pits; 66: non-septate fibres present; 69: fibres thin- to thick-walled.
• Axial parenchyma: 79: axial parenchyma vasicentric; 80: axial parenchyma aliform; 81: axial parenchyma lozenge-aliform; 83: axial parenchyma confluent; 91: two cells per parenchyma strand; 92: four (3–4) cells per parenchyma strand.
• Rays: 97: ray width 1–3 cells; 104: all ray cells procumbent; 106: body ray cells procumbent with one row of upright and/or square marginal cells; 115: 4–12 rays per mm; 116: ≥ 12 rays per mm.
• Storied structure: 120: axial parenchyma and/or vessel elements storied; 122: rays and/or axial elements irregularly storied.
• Mineral inclusions: 136: prismatic crystals present; 142: prismatic crystals in chambered axial parenchyma cells; (156: crystals in enlarged cells).

Trees grow slowly. The fruits open explosively on the tree and the seeds are dispersed over short distances. The seeds are eaten by monkeys such as mangabeys and black colobus, which sometimes open unripe fruits.

Baikiaea insignis usually occurs in swampy or periodically inundated forest along rivers and lakes, occasionally in well-drained localities in the forest. In Uganda it is found up to 1250 m altitude.

Collecting the seeds is difficult because the fruits open while still on the tree scattering the seeds, which should be collected from the ground. Seeds can be stored for several years in sealed containers in a cool locality. Ash can be added to reduce damage by insects; the seeds are susceptible to attack by weevils. Soaking the seed in cold water for 12–24 hours accelerates germination. Seeds are usually sown in pots. Wildlings are sometimes also collected for planting.

The trees can be managed by coppicing and pollarding.

After felling, logs should not be left in the forest for longer periods because they contain much sapwood, which is liable to borer attack.

There are no indications that Baikiaea insignis is threatened by genetic erosion. It is widespread and seems to be locally fairly common, and it is rarely selectively felled for timber.

The prospects for Baikiaea insignis as a timber tree of commercial importance are limited by the usually moderate size of the bole, by its preferred habitat in swampy and riverine forest, and by lack of information on growth rates, regeneration and suitable management practices. Baikiaea insignis may be an alternative for Baikiaea plurijuga Harms from southern Africa, which is well known as a producer of high-quality timber.

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• Brenan, J.P.M., 1967. Leguminosae, subfamily Caesalpinioideae. In: Milne-Redhead, E. & Polhill, R.M. (Editors). Flora of Tropical East Africa. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. 230 pp.

• Wilczek, R., Léonard, J., Hauman, L., Hoyle, A.C., Steyaert, R., Gilbert, G. & Boutique, R., 1952. Caesalpiniaceae. In: Robyns, W., Staner, P., Demaret, F., Germain, R., Gilbert, G., Hauman, L., Homès, M., Jurion, F., Lebrun, J., Vanden Abeele, M. & Boutique, R. (Editors). Flore du Congo belge et du Ruanda-Urundi. Spermatophytes. Volume 3. Institut National pour l’Étude Agronomique du Congo belge, Brussels, Belgium. pp. 234–554.

• W. Mojeremane, Department of Crop Science and Production, Botswana College of Agriculture, Private Bag 0027, Gaborone, Botswana

Mojeremane, W., 2012. Baikiaea insignis Benth. [Internet] Record from PROTA4U. Lemmens, R.H.M.J., Louppe, D. & Oteng-Amoako, A.A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. <http://www.prota4u.org/search.asp>.

Accessed 3 April 2025.

• See the Prota4U database.