Prota 7(1): Timbers/Bois d’œuvre 1
Bot. Jahrb. Syst. 23: 161 (1896).
Origin and geographic distribution
Trichilia gilgiana occurs from southern Nigeria east to eastern DR Congo, and south to northern Angola (Cabinda).
The wood is suitable for light construction, interior trim, vehicle bodies, furniture, cabinet work, boxes, crates, toys, novelties, veneer, plywood, hardboard and particle board, as well as pulpwood for paper production.
In Congo the bark is considered to have analgesic and stimulant properties and is used in traditional medicine to treat abdominal, chest and fever pains, and as a tonic. In DR Congo sap of young leaves is applied to circumcision wounds and small quantities of pulverized leaves are added to drinking water to treat respiratory problems in children.
The heartwood is greyish white to pinkish grey or pinkish brown and indistinctly demarcated from the creamy white sapwood. The grain is often interlocked, texture fine to moderately coarse. Quarter-sawn wood is lustrous and has darker stripes and irregular bands.
The wood is medium-weight, with a density of 570–650 kg/m³ at 12% moisture content. It air dries moderately well. The wood is not stable in service. At 12% moisture content, the modulus of rupture of wood from Mayombe (Congo) is 96 N/mm², modulus of elasticity 9200 N/mm², compression parallel to grain 45 N/mm², cleavage 13 N/mm² and Chalais-Meudon hardness 2.7.
The wood is difficult to saw because of the high silica content, which causes blunting of saw teeth and cutting edges. It planes satisfactorily, but quarter-sawn surfaces may be rough because of the presence of interlocked grain. The nailing properties are good, gluing properties moderate. The wood is not durable; it is susceptible to fungal, termite, dry-wood borer and marine borer attacks. The heartwood is resistant to impregnation by preservatives, but the sapwood is moderately permeable. The wood dust may cause irritation to the respiratory tracts and skin in wood workers.
Evergreen, small to medium-sized tree up to 30 m tall; bole branchless for up to 18 m, straight, cylindrical or fluted, up to 100 cm in diameter; bark surface smooth, greyish brown, peeling off in small plates, inner bark pale pink, exuding some latex; crown spreading, strongly branched; young branches short-hairy. Leaves alternate, imparipinnately compound with (2–) 5–8 pairs of leaflets; stipules absent; petiole 4–10 cm long, rachis (5–)10–26 cm long; petiolules 4–10 mm long; leaflets opposite, narrowly elliptical to narrowly ovate or narrowly obovate, 5–28 cm × 1.5–8 cm, cuneate to obtuse at base, acuminate at apex, glabrous but glandular dotted, pinnately veined. Inflorescence an axillary panicle up to 20(–30) cm long, short-hairy; bracts elliptical to ovate, up to 7(–10) mm long, usually persistent. Flowers unisexual, male and female flowers very similar in appearance, regular, 5-merous, creamy brown to pink, fragrant; pedicel 3–5(–8) mm long; receptacle cylindrical, 1–3 mm long; calyx cup-shaped, 2–3 mm long, lobes 1.5–2 mm long; petals free, narrowly elliptical to narrowly obovate, 7–10(–11.5) mm long; stamens 4.5–6.5 mm long, fused at base into a tube, hairy inside; ovary superior, pyramidal, c. 2 mm × 2–3 mm, densely hairy, 3-celled, style 2.5–4.5 mm long, hairy, stigma head-shaped; male flowers with rudimentary ovary, female flowers with non-dehiscing anthers. Fruit a pear-shaped to fig-shaped capsule 3–3.5 cm in diameter, with 0.5–1 cm long stipe, dehiscent, up to 6-seeded. Seeds c. 20 mm × 12 mm, on a long funicle, seed coat partly fleshy and orange-red, remaining part glossy dark brown. Seedling with epigeal germination; hypocotyl c. 4 cm long, epicotyl c. 4.5 cm long; cotyledons sessile, thick and fleshy.
The flowers are pollinated by insects such as bees. The seeds are eaten by birds, which may play an important role in dispersal.
Trichilia comprises about 90 species, most of them in tropical America. In continental Africa 18 species occur, in Madagascar 6.
The area of distribution of Trichilia retusa Oliv. overlaps largely with that of Trichilia gilgiana, but it is slightly larger, extending to southern Sudan and south-western Ethiopia in the north, and southern DR Congo in the south. Trichilia retusa is a shrub to small tree up to 15 m tall, characterized by its broadly notched leaflets. In Sudan the wood is used for pestles and mortars, whereas the fleshy seed coat is reportedly edible. In Congo bark scrapings are applied to swellings.
Trichilia rubescens Oliv. has a similar distribution, but extends to western Uganda and western Tanzania. It is also a shrub or small tree, differing from other African Trichilia species in its comparatively small flowers with distinct disk and obovoid to globose fruits 1–2 cm in diameter. The wood is used for poles, small implements and tool handles. It is also used as fuelwood and for making charcoal. Bark decoctions are used in traditional medicine to treat bronchitis, stomach-ache, diarrhoea, dizziness, insanity and sexual impotence. They are also administered as an enema to treat constipation and abdominal complaints. Root decoctions are applied as an enema to treat colic, and as anthelmintic and abortifacient. Young leaves are taken to treat gonorrhoea. The bark is used for making arrow poison. The fleshy seed coat is eaten in times of food scarcity. Antiparasitic limonoids were isolated from Trichilia rubescens leaves, and leaf extracts showed antimalarial activity.
Trichilia gilgiana is a common tree in lowland evergreen and semi-deciduous secondary forest, often in the understorey, up to 950 m altitude.
After felling, logs should be removed rapidly from the forest to dry, to prevent fungal and insect attacks, or they should be treated with preservatives.
Genetic resources and breeding
Trichilia gilgiana does not suffer from genetic erosion because it is fairly widespread and locally common in secondary forest.
The wood of Trichilia gilgiana is not particularly attractive and it is abrasive, while the often fluted boles hamper its applicability in the peeling industry. Therefore, the prospects as a commercial timber tree seem to be poor, and Trichilia gilgiana may remain an undesirable tree in exploited forest, as it often has been, like other Trichilia species.
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Correct citation of this article:
Lemmens, R.H.M.J., 2008. Trichilia gilgiana Harms. In: Louppe, D., Oteng-Amoako, A.A. & Brink, M. (Editors). Prota 7(1): Timbers/Bois d’œuvre 1. [CD-Rom]. PROTA, Wageningen, Netherlands.