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the web of life in southern Africa

Obetia tenax (Rock tree nettle, Mountain nettle)

[= Urera tenax]

Bergbrandnetel, Rotsbrandnetel [Afrikaans]; IuTiya [Swazi]; Lebabi, Mmabi [North Sotho]; Mbhadzwa, Mmabi [Tswana]; Muvhazwi ("stinging") [Venda]; imBati, imBadi enkulu [Zulu]

Life > eukaryotes > Archaeoplastida > Chloroplastida > Charophyta > Streptophytina > Plantae (land plants) > Tracheophyta (vascular plants) > Euphyllophyta > Lignophyta (woody plants) > Spermatophyta (seed plants) > Angiospermae (flowering plants) > Eudicotyledons > Core Eudicots > Rosids > Eurosid I > Order: Rosales > Family: Urticaceae


  • A deciduous shrub or small tree, reaching a height of 7 m.
  • All surfaces, including trunk, branches, leaves, flowers and fruit, covered with stinging hairs, that cause intense pain and blisters in contact with the skin.
  • Bark smooth, bronzy-brown or pinkish brown.
  • Watery latex present.
  • Leaves alternate, ovate, fleshy, 3 strong basal veins, 5-15 cm long by 3-10 cm wide with petiole up to 14 cm long, margin deeply toothed, apex broadly tapering, and base lobed.
  • Flowers are small, whitish to greenish-yellow, in short sprays in the axils of leaves.
  • Fruit small, ovoid, purplish brown nut, about 2-3 mm in diameter, clustered in spikes.

Distribution and habitat

From Komga in the Eastern Cape through to KwaZulu-Natal, Swaziland, Mozambique, Zimbabwe and Botswana. Grows on dry, rocky slopes and on granite outcrops, in bushveld.

Ecological interactions

  • Leaves and stems eaten by:
    • mammals
      • Diceros bicornis (Hook-lipped rhinoceros, Black rhinoceros) - according to Palmer & Pitman (1972) this is the only browsing mammal that eats this plant.
  • Used as a nesting site by:
    • birds
      • Phoeniculus purpureus (Green wood-hoopoe, Red-billed wood-hoopoe) - recorded nesting in pre-existing cavity in trunk.


  • Fibre from the bark is used to make cord and rope.
  • Leaves are boiled up as a vegetable (presumably boiling de-activates the stinging hairs.
  • The plant is used in traditional medicine.



  • Palgrave, K.C. and Palgrave, M.C. 2002. Trees of Southern Africa. 3rd Edition. Struik Publishers, Cape Town.
  • Palmer, E. and Pitman, N. 1972. Trees of Southern Africa covering all known indigenous species in the Republic of South Africa, South-West Africa, Botswana, Lesotho and Swaziland. Volume 1. A.A. Balkema, Cape Town.
  • van Wyk, B. and van Wyk, P. 1997. Field Guide to Trees of Southern Africa. Struik Publishers, Cape Town.

Text by Hamish Robertson