Prota 16: Fibres/Plantes à fibres
Kew Bull. 38: 226 (1983).
Urera tenax N.E.Br. (1888).
Tree nettle, mountain nettle, rock tree nettle (En).
Origin and geographic distribution
Obetia radula is distributed in Botswana, Zimbabwe, Mozambique, South Africa and Swaziland.
The bark yields a fibre which is made into tough cords, ropes, nets and mats. The bark is used for thatching. The leaf is cooked as a green vegetable (often mixed with that of Pouzolzia mixta Solms) and eaten with porridge. Root pulp is applied on snakebites.
The bark fibre is strong. The wood is soft and fibrous, with a spongy pith or hollow centre. Contact with the stinging hairs causes intense itching and burning, and may result in blisters on the skin.
Deciduous shrub or small tree up to 5(–7) m tall, presumably dioecious; outer bark purplish brown to grey, often longitudinally striate, large leaf scars present; younger branches densely covered with stinging hairs. Leaves alternate, simple; stipules free, lateral, lanceolate, 4–8 mm × 1–2.5 mm, apex long-acuminate, glabrous; petiole up to 14 cm long, with stinging hairs; blade ovate to almost circular, sometimes slightly 3-lobed, 3.5–15(–17) cm × 3–11.5(–19) cm, base broadly cordate, truncate or rounded, apex rounded, acute or broadly acuminate, margin coarsely toothed, upper surface with stinging hairs and a few stiff hairs, lower surface with scattered stiff hairs and stinging hairs along the veins. Inflorescence an axillary, much branched panicle, up to 10 cm long, with numerous stinging hairs. Flowers unisexual, very small, whitish to yellowish green; male flowers in dense inflorescences, regular, 5-merous, pedicellate, 1–2 mm in diameter, tepals usually with stinging hairs, rudimentary ovary present; female flowers solitary or in small clusters along axes and branches of inflorescence, 4-merous, shortly pedicellate, c. 1 mm long, outer pair of tepals smaller than inner pair, both pairs becoming thinly membranous, glabrous, ovary superior, ovoid, staminodes absent. Fruit an achene c. 1.5 mm long, compressed, ochre to brown, enc1osed by the persistent membranous perianth.
Obetia tenax flowers in August–September and fruits in October–November.
Obetia comprises 8 species, distributed in eastern Central Africa, East Africa, southern Africa and the Indian Ocean islands, mostly in dry habitats.
Obetia tenax occurs from sea level up to 1800 m altitude, in deciduous bushland in rocky locations.
Genetic resources and breeding
It is unknown whether Obetia tenax is threatened by genetic erosion.
Obetia tenax is a useful local source of fibre for cordage. Detailed information on the fibre properties is lacking, however, making it difficult to assess the prospects for this species. The presence of stinging hairs makes handling of the plant difficult.
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Correct citation of this article:
Brink, M., 2009. Obetia tenax (N.E.Br.) Friis. In: Brink, M. & Achigan-Dako, E.G. (Editors). Prota 16: Fibres/Plantes à fibres. [CD-Rom]. PROTA, Wageningen, Netherlands.