Obetia radula (stinging-nettle tree)
The stinging-nettle tree looks a bit like a papaya tree – but it does what its name suggests!
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 & 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.
Leaves of Obetia radula (Image: Henk Beentje)
A tree 5–13 m tall, with a sparsely-branched trunk up to 50 cm across, covered in stinging hairs. The leaves are clustered at the branch ends, and are much lobed, 15–25 × 15–25 cm, with stinging hairs all over. 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. The fruits are minute (less than 2 mm long).
Threats & 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 on-line in the Herbarium Catalogue.
Kew botanist Henk Beentje’s blog post: Stinging-nettle tree from Ngurdoto crater wall, Tanzania
Find out more about the stinging nettle (Urtica dioica)
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