Obetia radula (stinging-nettle tree)
The stinging-nettle tree looks a bit like a papaya tree - but it does what its name suggests!
Obetia radula in Ngurdoto Crater, Meru National Park, Tanzania
Obetia radula (Bak.) B.D.Jacks.
stinging-nettle tree (English); siyu (Lugishu); dorewa (Kamba); nakule (Rendille); ikope (Taita); elil (Tugen); amiandahy, amiana, ampy (Malagasy).
Not yet assessed according to IUCN Red List criteria, but thought likely to be of Least Concern.
Rocky hillsides in bushland.
Rope-making, basketry, medicinal.
The trunk and leaves bear stinging hairs, which can cause pain and intense itching to humans and animals on contact.
About this species
Tree-huggers beware – even the trunk of this tree has vicious stinging hairs, which cause both pain and intense itching. Think of European stinging nettle (Urtica dioica), which is from the same plant family (Urticaceae), and multiply! But from several steps away it is a pretty tree, looking a bit like a papaya tree (Carica papaya). It grows on rocky hillsides in East Africa and Madagascar and, amazingly, people have found a way of using the bark fibres for basketry and rope-making.
Geography and distribution
Obetia radula is known from only a rather narrow geographic band, stretching from eastern Congo-Kinshasa, through Rwanda, Burundi, Uganda, Kenya and north Tanzania, to Madagascar. It has been found at 500–2,000 m above sea level.
Overview: A tree 5–13 m tall, with a sparsely-branched trunk up to 50 cm across, covered in stinging hairs.
Leaves: The leaves are clustered at the branch ends, and are much lobed, 15–25 × 15–25 cm, with stinging hairs all over.
Flowers: The flowers are yellow-green and the male and female flowers are usually borne on separate trees in the axils of leaves. The male flowers are borne in groups up to 10 cm long, and are about 2 mm across. The female flowers are borne in groups up to 30 cm long, and are up to 8 mm across.
Fruits: The fruits are minute (less than 2 mm long).
Threats and conservation
Stinging-nettle tree occurs over a wide area, and there are no specific threats to either its habitat or the species itself. Hence, although an official conservation assessment has not been carried out, it is thought likely this species will be assessed as of Least Concern.
The stem fibres of Obetia radula are used to make rope and baskets. Some tribes use the roots as a remedy against barrenness (female infertility). The leaf is used in East Africa to deter rats and moles, as contact with the stinging hairs on the leaves causes intense itching in animals. In Madagascar the bark fibre was formerly used to ignite fires.
This species at Kew
Pressed and dried specimens of Obetia radula are held in the Herbarium, where they are available to researchers from around the world by appointment. The details of some of these specimens, including images, can be seen online in the Herbarium Catalogue.
Beentje, H.J. (1994). Kenya Trees, Shrubs and Lianas. National Museums of Kenya, Nairobi.
Brink, M. (2009). Obetia radula (Baker) B.D.Jacks. [Internet] Record from Protabase. Brink, M. & Achigan-Dako, E.G. (editors). PROTA (Plant Resources of Tropical Africa), Wageningen, Netherlands. (Accessed 11 March 2011). Available online.
Friis, I. (1983). A synopsis of Obetia (Urticaceae). Kew Bulletin 38: 221–228.
Friis, I. (1989). Flora of Tropical East Africa: Urticaceae. Balkema, Rotterdam.
Kew Science Editor: Henk Beentje
Copyediting: Emma Tredwell
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