Prota 7(1): Timbers/Bois d’œuvre 1
Taxon 24: 363 (1975).
Fagara davyi Verd. (1919).
Knobwood, forest knobwood, knobthorn (En).
Origin and geographic distribution
Zanthoxylum davyi occurs in Zimbabwe, eastern South Africa and Swaziland.
The wood is used for handles, walking sticks and fishing rods. It is suitable for heavy construction, heavy flooring, joinery, interior trim, vehicle bodies, furniture, cabinet work, mine props, ladders, sporting goods, agricultural implements, toys, novelties, musical instruments, boxes, crates and turnery.
The stem bark is used to treat cough, cold, boils, pleurisy, toothache and snakebites. The prickles are applied to infected wounds, the leaves to treat chest pain and as a poultice to heal sores, and the roots to treat mouth ulcers and sore throat, and as a tonic and aphrodisiac. The prickle-bearing protuberances on the bole have been used by children as toys, and have also been made into pipes.
The heartwood is pale greyish brown, often with greenish markings, fairly distinctly demarcated from the greyish sapwood. The texture is fine and even. Growth rings are distinct.
The wood is heavy, with a density of 830–930 kg/m³ at 12% moisture content. It air dries fairly rapidly in small dimensions, but larger boards are liable to surface checking. The rates of shrinkage are moderate, from green to oven dry 4.1% radial and 8.4% tangential.
The wood is strong and elastic. At 12% moisture content, the modulus of rupture is 128–140 N/mm², modulus of elasticity 15,700 N/mm², compression parallel to grain 55–57 N/mm², shear 15–17 N/mm², Janka side hardness 9210–10,450 N and Janka end hardness 9790–11,260 N.
The wood is fairly easy to saw and work in spite of its hardness. The polishing, gluing and bending properties are satisfactory. The wood is only moderately durable and susceptible to Lyctus attack. The heartwood is resistant to impregnation by preservatives.
The stem bark yielded 5 benzophenanthridine alkaloids. One of these, chelerythrine, is well known for its antimicrobial and anti-inflammatory properties. Crude stem extracts showed pronounced antibacterial activity against Escherichia coli, Shigella spp., Salmonella typhi and Streptococcus pyogenes, but no activity against Staphylococcus aureus.
Dioecious, medium-sized tree up to 30 m tall; bole usually straight and cylindrical, up to 60 cm in diameter, with conspicuous woody, prickle-bearing protuberances, sometimes slightly fluted at base; bark pale grey in younger trees to dark brown in older ones; twigs glabrous, armed with up to 5 mm long prickles. Leaves alternate, imparipinnately compound with (5–) 7–13 leaflets, up to 30 cm long; stipules absent; rachis channelled above, often with small prickles; leaflets opposite, sessile, slightly asymmetrically oblong to lanceolate or narrowly elliptical, 2–7(–10) cm × 1–3 cm, cuneate to obtuse at base, shortly acuminate and slightly notched at apex, margin finely toothed, glabrous, with glandular dots confined to the margin, pinnately veined with numerous lateral veins. Inflorescence a terminal panicle up to 6 cm long, with flowers in clusters. Flowers unisexual, regular, 4-merous, small; pedicel 1–1.5 mm long; sepals nearly free, c. 0.5 mm long; petals elliptical, c. 2.5 mm long, greenish yellow; male flowers with 4 stamens, ovary rudimentary; female flowers with superior, globose ovary and short style. Fruit a globose follicle c. 5 mm in diameter, glandular pitted, dehiscent, 1-seeded. Seed globose, c. 3 mm in diameter, black and shiny.
Zanthoxylum davyi flowers from October to January and fruits ripen about 3 months later.
Zanthoxylum is pantropical and comprises about 200 species, with tropical America being richest in species. Mainland Africa harbours about 35 species, whereas about 5 species are endemic to Madagascar.
Zanthoxylum davyi occurs in forest and forest patches, from coastal regions to mountainous areas; it is locally common in montane forest.
Genetic resources and breeding
The conservation status of Zanthoxylum davyi in South Africa is indeterminate, but in Zimbabwe it is considered endangered.
The information on Zanthoxylum davyi is too limited to judge its prospects as a commercial timber tree under sustainable exploitation management. However, stands of large trees are probably too scarce, and an inventory is needed.
The medicinal properties deserve more attention because of the claimed antimicrobial activities, which have been confirmed by pharmacological research.
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Correct citation of this article:
Lemmens, R.H.M.J., 2008. Zanthoxylum davyi (Verd.) P.G.Waterman. In: Louppe, D., Oteng-Amoako, A.A. & Brink, M. (Editors). Prota 7(1): Timbers/Bois d’œuvre 1. [CD-Rom]. PROTA, Wageningen, Netherlands.