Meet the trees of Namibia … The Kobas (Cyphostemma currorii = Cissus currorii)

•LUISE HOFFMANN CONSPICUOUS by its thick trunk covered in creamy smooth bark, this tree is quite common on the mountain slopes along the C28 and the D1982 in the vicinity of the Bosua- and the Us-pass.

Some kobas trees can be seen in more accessible places, for instance in Windhoek diagonally across from the Christuskirche in the small rockery next to the former State House as well as in Hugo Hahn Street close to its intersection with Nelson Mandela Avenue in Klein Windhoek.

A number of these trees add interest to the display of indigenous succulent plants at the Hosea Kutako International Airport. Another specimen grows in the ‘dip’ in the main road through Okahandja. At the entrance to the reception of the Ameib Ranch there is a kobas tree whose trunk is so thick that it takes three men with outstretched arms to reach around it.

Very beautiful and large kobas trees can be found on Moringa Guest Farm north of Wilhelmstal and on Roidina Nature Farm [photo] north of Omaruru. The kobas trees along the Us- und Bosua passes probably are the most southerly representatives of this species, which is otherwise fairly common in the Erongo and Brandberg mountains and on the slopes of the escarpment up to the Kunene River.

You will always find the kobas growing on dry rocky hill slopes, where it can survive because it stores much moisture in its thick smooth trunk. The smooth shiny bark reflects the heat and protects the trunk from evaporation. The tree is frequently multi-stemmed and may reach a height of seven metres, while normally the diameter of its trunk is about a metre. The papery bark is yellowish to pale brown, the underbark whitish to reddish.

The kobas tree flowers from October to December in areas where the onset of the rainy season is reasonably reliable but in response to rain as late as March under more arid conditions. The small greenish flowers form a spreading panicle and appear together with the succulent leaves.

Bunches of red berries develop from these flowers, indicating that this plant is related to the grapevine. But beware – these lovely red berries, in spite of their tempting appearance, contain a lot of oxalic acid, which is highly irritating to the mucous membranes. Yet, baboons will eat the fruit with impunity.

The thick succulent leaves develop fully only after the flowers have appeared. They consist of three leaflets attached to a long leaf stalk. Due to their content of oxalic acid they are rarely browsed. Thus these trees are adapted to their arid habitat not only by the shape and structure of their trunks but also by the succulent leaves, which store and preserve moisture, but fall off quite soon after the rains have stopped.

Names: A. kowas, kobas, botterboom; G. Butterbaum; H. omutindi; derivation of the genus name Cyphostemma is uncertain, currori in memory of the physician Dr A B Curror, who first collected this plant in Angola in 1840.

The kobas is protected by forestry legislation because in nature it grows very slowly. It is a characteristic and decorative tree in many gardens. Ask for seedlings at our new indigenous nursery “Namib trees” by contacting Carol at 081 127 3958 or Ivor at 081 127 1219.

Three additional cyphostemma species with thick succulent stems and smooth papery bark can be found in Namibia, nl:

Cyphostemma bainesii occurring from about Walvis Bay southwards along the escarpment up to about Keetmanshoop, always on rocky substrates on hill or mountain slopes. Without leaves it is difficult to distinguish from the other species except for its more southerly distribution and its smaller size.

Cyphostemma juttae occurs from Walvis Bay northwards up to the Kunene River and further east, e.g. up to Windhoek and in the Otavi Mountains. It seems to prefer dolomite. It rarely grows higher than two metres but may occasionally reach four metres. Initially the young blue-green leaves are simple though deeply lobed. Cyphostemma uter can be recognised by having five hairy leaflets, several bottle-shaped stems or one thick stem and occurring only in the north-western part of Namibia from about Outjo northwards and westwards. The smooth papery bark comes off in fairly large strips and has been used locally to transport honeycomb retrieved from bee’s nests by hunter-gatherers.

All these kobas species can be seen in the botanical garden in Windhoek.

They are a characteristic and decorative rockery species, but please remember that they are protected plants, because in nature they grow very slowly. They may therefore not be dug up or broken off. Cyphostemma currorii plants are found in many gardens and perhaps their owners will be prepared to give you a piece of their plant, for truncheons left to dry out for a few days grow fairly easily. Seedlings may be bought from the nursery of the National Botanical Research Institute. Beware of overwatering any kobas plant! Originating from very dry localities, they hate water logging and very easily rot under wet conditions.