Euphorbia vandermerwei stem

The stems of Euphorbia vandermerwei are usually four-angled or four-winged. The stem colour, olive green in picture, may also be bright green in cultivation or during comfort season, the young spines reddish to brick brown. The paired spines angle outwards laterally on small spine shields that are spaced up the winged stem ridges. The spines are mostly straight or nearly so, hard and thin. In the photo they are dark at the sharply pointed tips, pale grey at the base and all over when old. 

This plant was photographed growing out in the open in the Walter Sisulu National Botanical Garden in early winter (Smith, et al, 2024; iNaturalist).