Euphorbia grandicornis

Euphorbia grandicornis, commonly the cow horn, the well-armed euphorbia, the big-thorn euphorbia or in Afrikaans the renosterdoring (rhino thorn) or grootdoringnaboom (big thorn spurge), among more names, has formidable spines that have been described as living barbed wire, so beware! What does harm is easily called names.

The erect, green, succulent stems branch much, growing to heights from 1 m to 2 m. Plant width may match or exceed its height. There are three or sometimes four vertical, pale grey ridges or wings per stem, all zigzag and spiny. The ridges separate smooth, green, concave surfaces, variably blotched in paler shades. These green stem areas perform most of the photosynthetic duties, as the stem-tip leaves are tiny and short-lived.

The growth habit gives the plant a striking appearance: elaborately curving edges separated by intermittent, deep constrictions up the stem in consecutive sections. The spines grow in pairs along the cartilaginous ridges. The hard spines may be very uneven in size on older stems, reflecting plant wellbeing at the time when they emerged, also spine age differences. Spine length varies from 1,5 cm to 7 cm. It is by now unnecessary to test whether the effect of a spine on the human skin is painful.

Small yellow cyathia emerge in groups of three on stem-tip segment ridges, interspersed with the spines. Cyathia appear from early winter to early summer, the plant’s blooming season. Around these small “flowers” there are tiny bracts, variously coloured. The fruit capsules are thickly three-sectioned and red brown or mauve purple when ripe.

The species distribution in South Africa is in the north of KwaZulu-Natal and the southeast of Mpumalanga. It also grows in eSwatini, Mozambique and further in East Africa to Kenya.

The habitat is hot and dry Lowveld, bushveld and thicket. The species is not considered threatened in habitat early in the twenty first century. 

Vervet monkeys eat the flowers and the fruits. Black rhinos eat the plant. The flowers attract wasps and does not go unnoticed (Frandsen, 2017; Smith et al, 2017; Pooley, 1998; www.cactus-art.biz; www.forums.gardenweb.com; http://redlist.sanbi.org).