Prota 7(1): Timbers/Bois d’œuvre 1
Fl. trop. Afr. 1: 311 (1868).
Simaroubaceae (APG: Kirkiaceae)
White syringa, white kirkia, bastard marula (En).
Origin and geographic distribution
Kirkia acuminata is distributed in DR Congo and throughout southern Africa; possibly in Tanzania as well. It also occurs in South Africa.
The wood of Kirkia acuminata is used for poles and planks, household utensils (bowls, spoons), carts, musical instruments, tourist items, veneer and plywood. In South Africa the wood is made into furniture and floor blocks. The wood is also considered suitable for light construction, flooring, vehicle bodies, cabinet work, interior trim, agricultural implements, boxes and crates, core stock, matches, toys and novelties, turnery, hardboard and particle board, and as pulpwood. In Malawi the wood is made into charcoal.
Kirkia acuminata is often planted as a live fence. The bark fibre is made into cloth. The seeds and leaves are browsed by livestock. The swollen roots are used as a source of water in times of drought. In Zimbabwe an infusion of the bark is taken against vomiting and abdominal pain. An infusion of the root is taken to treat cough. The fruit sap is applied on wounds and as an antidote on snake bites. Pulverized roots are a remedy for toothache.
The heartwood is pale brown or green-brown, with an attractive dark brown veining; the sapwood is yellow-white or pale grey and up to 7.5 cm wide. The grain is usually straight, locally interlocked, the texture is fine.
The density of the wood is 580–720 kg/m³ at 12% moisture content. It is soft to moderately hard. Thin boards dry easily, but thick boards are difficult to season; splitting and surface checking may occur.
The wood saws easily, but rapidly blunts tools, due to the presence of silica crystals; frequent sharpening of cutting edges is necessary. The wood planes easily and turns fairly well. It polishes readily, glues satisfactorily and slices and peels well.
The durability of the heartwood is moderate, and the sapwood is susceptible to Lyctus borers. The heartwood is resistant to impregnation and the sapwood moderately resistant.
The seeds have an in-vitro dry matter digestibility of 39%. Per 100 g dry matter they contain: crude protein 11.0 g, neutral detergent fibre 61.0 g, acid detergent fibre 50.5 g, tannins 3.1 g, Ca 840 mg, Mg 430 mg and P 290 mg. Per 100 g dry matter the leaves contain: crude protein 8.1 g and neutral detergent fibre 11.8 g.
Semi-deciduous, monoecious medium-sized tree up to 20(–23) m tall; bole up to 90 cm in diameter; bark pale grey to grey, smooth, becoming fissured with age, with salmon-pink lenticels; crown large, rounded, spreading; branches marked with leaf scars. Leaves arranged spirally, clustered at ends of branches, up to 45 cm long, imparipinnately compound with (3–) 6–12(–20) pairs of leaflets, viscid when young; stipules absent; petiole 3–10 cm long; petiolules up to 2 mm long; leaflets opposite, narrowly ovate to lanceolate, 2–9(–11) cm × 1–2.5(–3) cm, base slightly oblique, apex acuminate, margin finely notched, glabrous or hairy, pinnately veined. Inflorescence an axillary thyrse up to 30 cm long, many-flowered; peduncle up to 20 cm long; bracts up to 2.5 cm long. Flowers functionally unisexual, regular, 4-merous; pedicel up to 6 mm long, jointed near base, whitish hairy; sepals almost completely free, ovate, 1–2.5 mm × 1–2.5 mm, glabrous or pubescent; petals free, lanceolate, 3–6 mm × 1–1.5 mm, glabrous or pubescent outside, greenish white to cream; stamens free, alternate with petals, in female flowers reduced and sterile; ovary superior, 4-locular, reduced in male flowers. Fruit oblong-ellipsoid, 4-sided, 8–25 mm × 5–11 mm, woody, pubescent to glabrous, separating into 1-seeded mericarps, each attached by a strip of tissue to top of central carpophore. Seeds almost as large as mericarp, rounded at one end and pointed at the other, 3-angled.
In southern Africa Kirkia acuminata forms new leaves in September–October, flowers in October–December and fruits from January onwards.
Kirkia comprises 5 species, distributed in tropical Africa from Ethiopia and Somalia to northern South Africa.
Kirkia acuminata is drought resistant and prefers hot and dry areas; it is susceptible to frost. It occurs up to 1600 m altitude in a range of habitats: bushland, woodland, savanna and rocky hillslopes. It prefers well-drained, basic soils, but may be found on various soil types, from alluvial flats and sandy or loamy soils near rivers to sandy and dry soils and rocky slopes.
Kirkia acuminata is easily propagated using seed or stem parts, and it is fast-growing.
Genetic resources and breeding
As Kirkia acuminata is widely distributed and occurs in a wide range of habitats, it is unlikely to be threatened by genetic erosion. It is, however, protected in South Africa.
The softness of the wood and the relatively wide sapwood restrict the usability of the wood of Kirkia acuminata, but the attractive figure of the wood makes it suitable for decorative purposes, e.g. for panelling and veneer. Kirkia acuminata has potential as an ornamental and shade tree.
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Correct citation of this article:
Brink, M., 2007. Kirkia acuminata Oliv. In: Louppe, D., Oteng-Amoako, A.A. & Brink, M. (Editors). Prota 7(1): Timbers/Bois d’œuvre 1. [CD-Rom]. PROTA, Wageningen, Netherlands.