Euphorbia inermis
| Light | Bright light with some direct sun; a few hours of gentle sun brings out the best form |
|---|---|
| Water | Moderately in growth; keep dry during winter dormancy |
| Soil | Fast-draining mineral mix (see Soil and potting mix) |
| Temperature | Keep above about 7 °C; USDA zones 9b–11 |
| Propagation | Cuttings (offsets) and seed |
| Toxicity | Toxic; the milky sap is a skin and eye irritant, and harmful if ingested |
Euphorbia inermis is a spineless, clumping succulent from South Africa, grown for its clusters of green, tentacle-like stems that radiate outward from a fat central body. Belonging to the group of medusoid euphorbias — so named for their resemblance to the snake-haired Medusa — it forms a low, spreading mound of finger-thick branches over a squat, partly buried caudex, and is sometimes sold under the common name green crown. Like all members of the genus Euphorbia, it produces a milky white latex when cut.
Description
Euphorbia inermis grows from a thickened, tuberous central stem (a caudex) that in cultivation often sits partly above the soil. From the top of this body radiate numerous slender, cylindrical branches, each a few millimetres to roughly a centimetre thick and typically 10–20 cm long, arranged in a low rosette that spreads and clumps with age. As the common name of the medusoid group suggests, a well-grown plant looks like a nest of writhing green tentacles.
The stems are smooth and spineless (the epithet inermis means "unarmed"), marked with faint tubercles where old leaves and flower stalks were once attached. Small, narrow leaves appear briefly at the growing tips and soon drop. The plant is monoecious, with male and female flowers carried on the same plant; the tiny flowers, borne in specialised structures called cyathia, are a soft yellow-green and can carry a faint scent.
Distribution and habitat
The species is native to the Eastern Cape of South Africa, where it grows in arid, rocky scrub and grassland. In habitat the caudex sits largely below ground, protected from sun and drought, with only the radiating stems exposed at the surface among rocks and low vegetation. This growth habit is a classic adaptation to a climate of hot, dry spells broken by seasonal rain.
Cultivation
Euphorbia inermis is an undemanding plant for anyone who already grows other caudiciform succulents. Pot it in a gritty, very free-draining mix and give it bright light with a few hours of direct sun, which keeps the stems compact and richly coloured; too little light draws the branches out thin and pale. Water moderately through the warm growing season, always letting the mix dry out before watering again, and keep the plant dry and cool through its winter rest to prevent rot. See Watering and Repotting for general technique.
Many growers raise the caudex progressively at each repotting to show it off, though in the wild it would be buried. Take care when handling or pruning: the milky sap is an irritant (see below).
Propagation
The species is readily increased from cuttings — individual stems detached from the clump root without much fuss. Let each cutting callus over for several days in a dry, shaded spot so the sap seals and the wound dries before setting it in a gritty mix; this greatly reduces the risk of rot. Seed is also possible but less common in collections, and usually calls for hand-pollinating the small cyathia — often between two plants, as many euphorbias set little seed when selfed. See Propagation — cuttings and Propagation — seed for full walkthroughs.
Common problems
- Rot — the usual killer, brought on by overwatering, a poorly draining mix, or watering during winter dormancy; the caudex or stem bases soften and discolour.
- Etiolation — in weak light the stems stretch long, thin and pale, losing the tight medusoid form.
- Irritant sap — the milky white latex is toxic and irritating to skin and especially the eyes. Wear gloves, avoid touching your face, and keep the plant away from children and pets.
- Pests — mealybugs (white fluff around the crown and roots) and the occasional spider mite are the main nuisances; see Pests and diseases.
See also
- Euphorbia — the genus overview
- Soil and potting mix · Watering · Repotting · Propagation — cuttings · Pests and diseases