The genus Euphorbia is one of the giants of the plant world, with roughly 2 000 species ranging from tiny annual “weeds” to sizeable shrubs and trees.

Many of the most charismatic members are the succulent spurges of Africa, where thickened, photosynthetic stems and water-storing roots allow them to thrive in semi-arid Karoo, savanna and bushveld landscapes. At a glance many of these plants are easily mistaken for cacti, yet they belong to a completely different family and are united instead by their unique flower structure, the cyathium – a tiny cup that holds the actual male and female flowers and nectar glands.

Almost all Euphorbia species exude a milky white latex when damaged. This sap has helped the genus to succeed as it seals wounds and has antifungal and antibacterial properties, but it is also irritating and sometimes highly toxic to skin, eyes and mucous membranes, so care and gloves are strongly recommended when pruning or transplanting.

For South African gardeners and collectors, the succulent euphorbias offer tough, water-wise structure for rock gardens, containers and xeriscapes. Their sculptural stems, intricate spination and neat clusters of yellowish cyathia are especially striking in late spring and summer. The species below are all South African endemics with fascinating forms and restricted natural distributions, making them rewarding subjects to grow from seed and a meaningful contribution to ex-situ conservation when sourced responsibly.

Euphorbia knobelii

This is a compact, shrubby euphorbia forming a short woody trunk with many arching branches that radiate from near ground level. The stems are four-angled, prominently spiny and often beautifully banded or variegated in shades of deep to grey-green, giving the plant an almost sculptural, candelabra-like presence even at modest size.

Euphorbia knobelii is endemic to the North West Province of South Africa, where it is known mainly from the Marico district north of Zeerust.

It grows on rocky hills and ridges in bushveld vegetation, experiencing hot summers, summer rainfall and cool, dry winters. Field monitoring has documented an estimated 50–60% population reduction over the past three decades, driven by habitat degradation and disease, and the species is listed as Endangered.

The flowers of Euphorbia knobelii are borne as small clusters of cyathia along the upper parts of the stems, typically yellow to yellow-brown, sometimes with reddish tints, and appearing mainly in the warmer months of spring and summer.

In the garden or on the patio this species prefers a bright, sunny position with excellent drainage and a lean, gritty substrate. Once established, it is strongly drought tolerant but responds to occasional deep watering in summer with fresh, vigorous growth. Seed-grown plants develop into sturdy, architectural shrubs over time, perfect for dramatic pottery such as rugged, bark-textured containers where the contrast between rough ceramic and geometric green stems can be fully appreciated.