Euphorbia cooperi – Cooper's Spurge
Euphorbia cooperi is a succulent, tree-like candelabra spurge from the spurge family (Euphorbiaceae), one of the few truly "tree-like" representatives of the Euphorbia genus. It originates from the warm bushveld of southern and eastern Africa and is valued as a plant with a distinctive, architectural form – fleshy, segmented stems form a candelabra-shaped crown set on a bare, gray trunk.
Synonyms and nomenclature
The species was described by N.E. Brown (1907). In the POWO database, the species name is "clean" – it shows no synonyms. However, three varieties are distinguished, and the only widely encountered synonym appears at the variety level:
- Euphorbia ussanguensis N.E.Br. = Euphorbia cooperi var. ussanguensis
- accepted varieties: var. cooperi, var. calidicola, var. ussanguensis
In English, the plant is known as Bushveld Candelabra Tree, Transvaal Candelabra Tree, and Candelabra Euphorbia; in Afrikaans – Transvaalse kandelaarnaboom, in Zulu – umhlonhlo. The Polish name wilczomlecz Coopera is a commercial calque.
Botanical description and appearance
In nature, the plant usually reaches about 7 meters in height (up to 9 m in extreme cases). The bare, gray trunk grows up to 3 m tall and about 35 cm in diameter, with scars from fallen branches, and supports a rounded, flattened crown. The succulent stems are fleshy, distinctly 4–6-winged, and constricted into segments, giving them the appearance of a "string of beads."
Paired, short (5–7 mm) spines, gray with darker tips, are set on the woody edges of the wings. Leaves are rudimentary and fall off quickly. Small, yellow-green to golden cyathia appear in clusters at the branch tips in early spring (September–October in the southern hemisphere), followed by the formation of three-lobed capsules with a reddish tinge.
Growth rate and frost tolerance
The growth rate is slow to moderate, typical for tree-like succulent euphorbias. The species comes from warm, seasonally dry shrublands and does not tolerate frost – the safe minimum temperature is about -3 to -4°C for short periods, with dry soil. It corresponds to USDA zone 10 (approximately 9b–11); outdoor cultivation in temperate climates is not feasible.
Cultivation in temperate climates
Cooper's spurge is grown in a pot as an impressive structural plant. It requires full sun and very well-draining, mineral soil suitable for succulents and cacti. Watering must be sparing: from spring to autumn after the top layer has dried out, and greatly reduced in winter – excess water quickly leads to stem and root rot. Wintering should be bright, dry, and at a positive temperature, approximately 5–12°C; the plant must not be exposed to frost. Exposure to strong sunlight after winter should be increased gradually to avoid burns.
Cultivation from seeds
Seeds are sown in spring, optionally after soaking for about a day, in warm (20–25°C), sterile, and very well-draining substrate. Germination usually occurs within 1–3 weeks but can be uneven and capricious – seed freshness, warmth, and avoiding excess moisture, which promotes seedling rot, are crucial. Propagation from cuttings is easier, but sowing from seeds produces the healthiest, independently rooted plants.
Safety – milky sap
The milky sap of Euphorbia cooperi is highly irritating and toxic to humans and animals. Contact with skin can cause blisters, fumes near the "bleeding" plant cause throat burning, and contact with the eyes can cause serious damage, including loss of vision. When cutting and repotting, gloves and eye protection should be used, and the plant kept away from children and pets.
Uses and suitability
This is primarily a collector’s and ornamental-architectural plant – a strong accent in succulent collections, on windowsills, balconies, or terraces in summer, as well as in winter gardens and greenhouses. Growing an adult specimen is not difficult (sun, drainage, little water), but the capricious seed germination and toxic sap mean the species is best suited for collectors and those experienced with growing euphorbias.
Interesting facts
The species name commemorates Thomas Cooper, a 19th-century English botanist who collected plants in South Africa. The caustic sap was used by local people as a fish poison – a bundle of grass soaked in latex was thrown into the water, and paralyzed fish floated to the surface. Due to its stinging sap, this plant is avoided by livestock and wild animals.
Summary
Euphorbia cooperi is one of the most striking tree-like spurges – its candelabra shape, segmented stems, and low water requirements make it a graceful sculptural plant for succulent collections. It only needs sun, good drainage, and caution due to its toxic sap, rewarding with its distinctive "desert" silhouette all year round.
