Euphorbia caerulescens aka Blue Noors

Euphorbia caerulescens is a succulent shrub in the spurge family. Its common names include blue euphorbia and sweetnoors. It comes from South Africa’s Cape Province, including the Noorsveld. Its native climate is subtropical. It grows on rocky ground, chiefly on north-facing hill and mountain slopes. It also occurs on hilltops and in other sites. Many other succulents share its habitat, but grasses are scarce. In some places, it forms much of the vegetation.

Plants reach about 1.6–4.9 feet [0.5–1.5 metres] tall. Underground shoots let clumps spread almost as wide. Thick, upright stems form an uneven crown with many short branches. Their shape recalls a cactus, though this is a euphorbia. The stems look blue-grey and have four to six angles. Narrow points divide them into short sections. Broad sections mark times of faster growth; narrow sections mark slower growth. Small leaves appear on new growth, then soon fall.

Paired spines line the ridges and range from white to dark brown. They can reach about 0.16 feet [0.05 metres] long. Yellow flower structures called cyathia grow near the branch tips. They sit between spine pairs, in groups of one to three. The stems, clumping shape and spines provide its main garden interest. In suitable sites, it can become a large landscape feature within five to ten years.

Give this plant full sun and soil that drains freely. It also tolerates some shade, and young plants can grow indoors. Move shade-grown plants into stronger sun in stages to prevent scorch. Use an airy mix made mostly from mineral materials. Add only a little peat or leaf mould. Water during active growth, from March to September. Never leave water standing around the roots. Keep the plant almost dry through winter. It needs frost-free conditions and shelter from strong winds.

Wind can force stems together and leave lasting scars. Once settled, this long-lived plant can stay in place for years. It also suits small pots. Repot in late winter or early spring. Cuttings can root in late spring or summer. Let cut ends dry for one or two weeks before planting. Take care around its latex sap. It can irritate skin and eyes, and swallowing it can burn the throat.