This plant, Euphorbia grandicornis, cow horn or renosterdoring (rhino thorn) in Afrikaans, has formidable spines that have been described as living barbed wire. There are erect green succulent stems with three or four vertical zigzag spiny ridges between the smooth, wide, concave surfaces. These green stem surfaces perform most of the photosynthesis duties as the leaves are tiny and short-lived.
Plant size is about 2 m tall and due to much branching, similar in width. This gives the stems a striking appearance with their wing-like edges and intermittent constrictions up the stem between consecutive sections. The spines grow in pairs along the cartilaginous ridges up the stems. These paired spines may have very uneven sizes on older stems, reflecting the differences in duration of their growth.
At the stem tops on the upper segments small yellow cyathia in groups of three are interspersed with the spines. They appear in late spring and early summer, the plant’s blooming season. Around these small “flowers” there are tiny bracts, variously coloured. The seed capsules are three-sectioned and purple when ripe.
It grows in KwaZulu-Natal to Kenya along the eastern parts of southern Africa (www.cactus-art.biz; www.forums.gardenweb.com).