Euphorbia aeruginosa aka Crimson Needle

Euphorbia aeruginosa is a small, spiny succulent in the spurge family. It also goes by the name miniature saguaro. Kew places its native range in northern Limpopo, South Africa. LLIFLE describes plants from the Soutpansberg slopes and Limpopo valley. It grows in rock cracks in a dry landscape. Its form varies with the site and the individual plant.

Plants reach about 0.5–1 foot [0.15–0.30 metres] tall. Wild plants can reach 1.3 feet [0.40 metres]. A thickened stem base, or caudex, lies mostly underground. Thick roots merge with this base. Branches arise near the soil and higher on the plant. Sun-grown plants form tight clumps, while shaded plants can spread almost flat. The slender stems look blue-grey, green-brown, or copper-green. They have four or five faint angles and may twist. Paired red-brown spines stand out against the stems. The name refers to their copper-green colour.

Small yellow flower heads, called cyathia, line the stems. They appear from late winter through spring. Each measures about three millimetres across. Small, blunt-lobed capsules follow the flowers. Each capsule holds three seeds with a bumpy surface. The plant can flower freely in pots. Its coloured stems and spines also give it value as a container plant. With time, its many stems can fill a bowl about 1 foot [0.30 metres] wide.

This species is fairly easy to grow in pots. It needs a mineral-rich mix that drains very well. Bright light helps keep its growth compact. Light shade brings out the spine colour. Tolerance of full sun varies between plants. Strong sun all day can bleach the stems. Too little sun leads to loose growth that may need support. Large, poorly supported branches may break away. Moderate watering suits active growth, with average feeding during summer.

Cold, wet conditions make rot a concern. Keep dormant plants dry at around 4°C in winter. The species can endure light frost, but outdoor plants face greater frost risk. Growers raise new plants from seed or stem cuttings. Cut surfaces need about a week to dry before planting. Fresh cuts can rot before roots form. Seeds may sprout within one to three weeks in a sandy seed mix.