Meet the Trees … The Milkbush – (Euphorbia damarana and Euphorbia gregaria)

• LUISE HOFFMANNANYONE traveling through the Namib will notice these many-stemmed grey green shrubs of 1 – 3 m height with many erect rod-like branches, so common along the B2 between Usakos and Swakopmund or the B4 between Seeheim and Aus.

Names: A. melkbos; G. Beseneuphorbie (E. damarana) und Namibmilchbusch (E. gregaria) N/D. kuib. The specific name damarana indicates that this shrub occurs mostly in Damaraland, while gregaria may either refer to the clustered arrangement of the flowers of this species or to the fact that E.gregaria always occurs in large groups.

Euphorbia damarana is restricted to the gravel plains of the central Namib from the Tropic of Capricorn northwards into southern Kaokoland and is endemic to Namibia. E. gregaria is near endemic and only occurs from about Helmeringhausen southwards to the Orange River.

Both species form large, dense, many stemmed shrubs, branching from the base and consisting of large numbers of erect branches arising from a central woody piece of tissue at ground level. The German name „Beseneuphorbie” or ‘broom euphorbia’ refers to this habit. A few secondary branches are sometimes found near the tip of the primary branches. E. damarana reaches a height of 2 to 3 m and a diameter of 3 to 5 m. E. gregaria is only about 1.5 m high and also has a smaller diameter.

The tough, stringy branches are covered by a grey-green bark. When bruised, the stems exude a sticky milky latex, less poisonous than that of Euphorbia virosa, but also very painful and irritating in the eyes. Leaves are found occasionally on young growth.

The flowers are succulent structures surrounded by a cuplike growth, covered by dense tawny hairs and arranged in clusters towards the tip of the branches. Male and female flowers occur on different plants.

The fruit are rounded capsules somewhat similar in shape to a fig, consisting of 4 – 6 compartments. Those of E. damarana grow almost erect on short stems, while those of E. gregaria are somewhat larger and hang from a longer and curved little stem. Remarks: In spite of the poisonous latex E. damarana is browsed by kudu and rhino in winter and half-chewed remains may be found around the shrubs, especially during a drought. Small mammals collect the seeds, even though they are poisonous for humans.

A parasite called Hydnora africana, (Afr: jakkalskos, bobbejaankos, N/D: kannip, kauimp) and only noticeable on account of its very strong carrion odour grows on these plants. Its only visible part is the flower, 10 – 20 cm long, emerging from the 5 – 7 angled, warty subterranean rhizomes. The lower part of the flower is tubular, while the upper two thirds are divided into three converging points.

On the inside these are covered by a soft spongy layer of tissue, which emits the terrible smell, attracting insects for pollination. The fruits resembling potatoes with many seeds develop in the tubular part of the flower.

They are eagerly eaten by porcupine, baboons, and jackals (Afr. name). Humans usually roast these fruits before eating them. This parasite only occurs on Euphorbia- and Zygophyllum species. Dry branches of these two milkbushes burn brightly and probably contain some flammable substance.

Currently investigations are underway to utilise the fibres of E. gregaria. However, it is already apparent that regrowth is very slow.

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