Euphorbia heptagona scattered thorns on stem ridges

This Euphorbia heptagona plant used to be known as E. atrispina, sometimes commonly the rock barrelwort and in Afrikaans the swartdoringnoors (the black thorn spurge).

It grows here many cylindrical, green branches, all longitudinally angular and rounded at tip and base. Branching occurs at the base from the strong central root. Young plants may appear like tiny trees or spreading shrublets. As the undisturbed plant matures it may assume a mounded cushion shape with a large number of stem tips visible in a dome-like structure.

The squat columnar stem has about seven to nine lateral ridges where sharp, long spines persist for some time. The spines are purplish red to black when young. The flowers are small and yellow, appearing in spring at the tips of the new spines from the stem tops. The fruits are globose and purple in colour.

E. atrispina used to have two varieties, viz. var. atrispina and var. viridis before the lumping (Euston-Brown and Kruger, 2023; Smith, et al, 2017; Vlok and Schutte-Vlok, 2015; Van Jaarsveld, et al, 2006; Bond and Goldblatt, 1984; iNaturalist; www.learn2grow.com).