Euphorbia gymnocalycioides
| Light | Bright light with some protection from the harshest afternoon sun |
|---|---|
| Water | Sparingly; let the soil dry out fully between waterings, keep dry in winter |
| Soil | Very free-draining mineral mix (see Soil and potting mix) |
| Temperature | Keep warm and above freezing; USDA zones 10–11 |
| Propagation | Seed (primary); cuttings possible but tricky |
| Toxicity | Toxic — milky latex irritates skin and eyes (see Euphorbia) |
Euphorbia gymnocalycioides is a rare, dwarf globular succulent from southern Ethiopia, famous among collectors for looking uncannily like a cactus rather than a euphorbia. Its ribbed, tubercled green body so closely resembles a plant in the genus Gymnocalycium that the resemblance is written into its name — a striking case of convergent evolution between an African euphorbia and a South American cactus.
Description
Euphorbia gymnocalycioides is a small, solitary, more-or-less spherical to shortly cylindrical plant, typically only a few centimetres across. The body is divided into low, rounded ribs broken into blunt tubercles, giving it the chinned, geometric look of a Gymnocalycium cactus. Unlike a true cactus, however, it bears no spines and — like all euphorbias — carries a milky white latex inside.
The plant is dioecious, meaning individuals are either male or female, so seed can only be set when plants of both sexes flower together. The tiny cyathia (the specialised euphorbia "flowers") are borne near the crown and are modest compared with the showy blooms of the cactus it mimics. A short, thickened rootstock helps the plant survive dry spells.
Distribution and habitat
The species is known from a very limited area in southern Ethiopia, where it grows in dry, rocky ground among low scrub. Like many narrowly endemic succulents, it occupies a small natural range and is uncommon in the wild, which makes responsibly propagated plants especially important to the hobby.
As with the entire cactus and succulent trade, wild collection is discouraged; nursery-raised seedlings are the proper source. Like all succulent Euphorbia species, it is listed under CITES Appendix II, so international trade in the plants is regulated.
Cultivation
This is a choice, slightly demanding plant best suited to a grower with some succulent experience. Grow it in a very gritty, mostly mineral mix in a small pot with excellent drainage, in bright light with a little shade from the fiercest afternoon sun. Warmth is important: keep it comfortably above freezing year-round.
Water carefully during the growing season, always letting the mix dry out completely before watering again, and keep the plant dry through the cooler months to prevent rot — the commonest cause of loss. Take care when handling or cutting the plant, as the latex is an irritant; see the Euphorbia genus page for safe-handling notes. General technique is covered under Watering and Repotting.
Propagation
Seed is the usual and most reliable method, though because the species is dioecious you need flowering male and female plants to obtain viable seed. Sow on a warm, mineral surface kept humid until germination; see Propagation — seed for a full walkthrough.
Vegetative propagation is more difficult. The plant seldom branches, so cuttings are rarely available, and any cut surface must be allowed to stop bleeding and callus before rooting — see Propagation — cuttings. Some growers graft rare or slow euphorbias like this onto a more vigorous rootstock to speed growth and safeguard a plant.
Common problems
- Rot — nearly always from overwatering, a wet winter, or a slow-draining mix; the body softens and discolours, often from the base.
- Etiolation — too little light makes the body pale and stretch upward, losing its neat globular shape.
- Pests — mealybugs (white fluff between the tubercles and at the roots) and spider mites are the usual offenders; see Pests and diseases.
See also
- Euphorbia — the genus overview
- Gymnocalycium — the cactus genus it mimics
- Grafting · Soil and potting mix · Watering · Propagation — seed · Pests and diseases