Euphorbia guillauminiana
| Light | Bright light to some direct sun; full sun once established |
|---|---|
| Water | Water in growth; keep dry during leafless dormancy |
| Soil | Very free-draining mineral mix (see Soil and potting mix) |
| Temperature | Warm-growing; keep above roughly 12 °C, no frost |
| Propagation | Seed; cuttings (rooted with care) |
| Toxicity | Milky latex is a skin and eye irritant; toxic if ingested |
Euphorbia guillauminiana is a small caudiciform succulent from Madagascar, grown for its swollen, water-storing stem and clusters of bright yellow flowers. It forms a compact, shrubby plant on a thickened base, and belongs to the vast and varied genus Euphorbia, which spans everything from tiny pebble-like succulents to tree-sized giants.
Description
Euphorbia guillauminiana builds a swollen, semi-woody stem or caudex from which several thickened branches arise, giving older plants a bonsai-like, top-heavy look. The branches are grey to brownish and firm, storing water against Madagascar's long dry season. Small, ovate green leaves flush from the branch tips during the growing period and are shed as the plant goes dormant, leaving a bare, sculptural framework.
The flowers are the main draw: like all euphorbias the true blooms are tiny, but they are framed by showy bright yellow bracts (cyathophylls) carried in clusters at the branch ends, often appearing with or just after the new leaves. As with every member of the genus, cut or broken tissue exudes a milky white latex.
Distribution and habitat
The species is endemic to Madagascar, where it grows in seasonally dry, warm habitat on rocky or gritty ground. Plants there endure a pronounced dry season by dropping their leaves and drawing on the reserves held in the swollen stem, then leafing out and flowering when the rains return. Like the rest of its habitat's flora, it is adapted to sharp drainage and strong light. Its natural range is very restricted, and — as with all succulent euphorbias, which are listed on CITES Appendix II — wild plants are pressured by illegal collection for the plant trade, so cultivated material should come from nursery-propagated stock.
Cultivation
Euphorbia guillauminiana is prized by caudiciform collectors but rewards a careful hand with the watering can. Grow it in a very free-draining, mostly mineral mix in a pot that is not too large, in bright light with some direct sun to keep the plant compact and encourage flowering. It is a warm grower with a clear seasonal rhythm: water regularly while it is in leaf and growing, then taper off and keep it dry through its leafless rest. Cold, damp soil is the enemy — keep it warm (comfortably above about 12 °C) and protect it from any frost.
Overwatering, especially during dormancy or in cool weather, is the usual cause of loss, as the swollen base rots readily when kept wet. See Watering and Repotting for general technique.
Handling: the milky latex is an irritant to skin and especially the eyes; wear gloves and wash any sap off promptly when pruning or repotting, and keep the plant away from pets and children.
Propagation
The species can be raised from seed, which best preserves the natural caudiciform habit, and also from cuttings. To take cuttings, allow the cut surface and its bleeding latex to dry and callus for several days before setting the cutting in a barely moist, gritty mix; bottom warmth helps rooting. Cutting-grown plants tend to be branchier and slower to develop a fat basal caudex than seedlings.
Common problems
- Rot — from overwatering, cold-wet conditions, or watering during dormancy; the base or branches soften and discolour.
- Leaf drop out of season — usually a normal response to cold, drought stress, or the onset of dormancy rather than a disease.
- Pests — mealybugs (white fluff at the branch joints and roots) and spider mites are the most likely troublemakers.
See also
- Euphorbia — the genus overview
- Soil and potting mix · Watering · Repotting · Propagation — seed · Propagation — cuttings · Pests and diseases