Meet the Trees of Namibia … The Angola Nettle (Obetia carruthersiana)

• LUISE HOFFMANNTHE most obvious feature of the Angola Nettle is that the entire plant – leaves, stems and branches – is densely covered in thousands of stinging prickles about 2-3 mm long.

In comparison to the Namibian vegetation in general, it has large, intensely green leaves, which makes it very decorative on the rocky outcrops and hill slopes in central and northern Namibia where it occurs.

Names: G. Baumnessel, Brennesselbaum, Angola-Nessel; E: Angola nettle, nettle-tree; A. Angola-brandnetel, suidwes-brandnetel. In the National Herbarium I found the Otjiherero name “omutiwonyoka” meaning ‘snake tree’, also mentioned for the carrot tree (Steganotaenia araliacea).

As I understand, this name is generally used for several tree species with dense foliage, which might harbour unpleasant surprises such as leopards, snakes, red wasps, etc or, in this case, stinging prickles. These prickles cause an intensely painful burning sensation when touched, which however subsides on its own after a while. No explanation for the genus name obetia could be found.

The specific name carruthersiana refers to the botanist W Carruthers, a former curator of the herbarium at the “British Museum” in London. The epithet ‘Angola’ indicates that the type specimen, that is the first specimen of this species to be officially recorded, was found in that country.

The Angola nettle is a many-stemmed shrub of up to three metres, rarely a tree of up to six metres, with erect branches, a reddish brown smooth bark, which is paler on young branches. The numerous prickles arise from dark brown swollen bases.

The large heart-shaped leaves are dark green, prickly on both surfaces and can reach a size of 20 x 15 cm. Their margins are coarsely serrate and the midrib is prominent below. They only appear after the flowers.

Male and female flowers grow on separate plants and are arranged in terminal sprays. They are numerous, tiny, greenish to white and appear from August to December, giving rise to tiny nuts enveloped in enlarged flower parts.

No medicinal or commercial uses for the Angola nettle are recorded. The prickles are long enough to be removed with tweezers but being so numerous, this can be a daunting task. Therefore, it is better to give these plants a wide berth.

Prickles of this kind contain allergenic substances in their cell sap. The tip of the prickle is bulbous and silicified, meaning it has a consistency similar to that of very fine glass. When touched, it breaks off diagonally thus turning it into a tiny hypodermic needle, which injects these allergenic chemicals into the skin.

In nature you will only find the Angola nettle if you clamber around on stony outcrops or hill slopes. Years ago I saw one of them behind the main building of a hotel just north of Prosperita. That hotel initially had a very interesting completely indigenous garden consisting mainly of succulents from north-western Namibia.

Unfortunately over the years it became overgrown by various self-seeded plants. The unusually wet rainy season of 2010-11 with three times the local average, followed immediately by unusually cold weather killed many of the succulents.

However, it is still worthwhile to take along your tree book and see if you can identify some of the Cyphostemma, Commiphora, Sesamothamnos and Sterculia species.

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