Euphorbia primulifolia
| Light | Bright light to a little shade; more light and colour during the growing season |
|---|---|
| Water | Water regularly while in leaf; keep dry during dormancy |
| Soil | Very free-draining, gritty mineral mix (see Soil and potting mix) |
| Temperature | Keep frost-free and above about 10 °C; USDA zones 10–11 |
| Propagation | Seed; occasionally division of clustered heads |
| Toxicity | Toxic — the milky latex is caustic and irritating to skin, eyes and if ingested |
Euphorbia primulifolia is a small, caudex-forming succulent Euphorbia from Madagascar, grown for the neat rosette of leaves it carries on top of a squat, partly buried tuber. The caudex sits at or just below soil level and pushes up a low, primrose-like cluster of broad green leaves, giving the plant its species name and a distinctly un-cactus-like look among the succulent euphorbias.
Description
Euphorbia primulifolia grows from a thick, rounded to elongate tuberous caudex that stores water and food through the dry season. From the crown of this tuber the plant produces a tight rosette of obovate to spoon-shaped leaves, soft green and often held nearly flat against the soil, the arrangement recalling a primrose or a small rosette plant rather than a typical spiny euphorbia.
Like most members of the genus, its true flowers are tiny and enclosed in specialised cup-shaped structures called cyathia. These are small and pale, greenish-white to pink, and often appear before or alongside the emerging leaves. The plant is deciduous in cultivation, dropping its leaves and drawing down into the caudex when it goes dormant, then leafing out again when watering and warmth resume.
Distribution and habitat
The species is endemic to Madagascar, where it grows in seasonally dry habitats and roots among rock and gritty, sharply drained soils. In habitat the caudex sits largely buried, protecting it from heat and drought, with only the leaf rosette exposed during the growing season. Plants experience a pronounced wet-and-dry cycle, and their deciduous, caudex-storing habit is an adaptation to that rhythm.
As with much of the succulent trade, the succulent species of Euphorbia — including this one — are listed under CITES Appendix II, so international movement of plants is regulated; nursery-raised specimens are the appropriate source for collectors.
Cultivation
Euphorbia primulifolia is a rewarding caudiciform for the intermediate grower, and its main requirements are sharp drainage and respect for its seasonal cycle. Grow it in a very open, mostly mineral mix in a pot that lets the roots and tuber dry quickly after watering. Give it bright light; a little shade is fine, but too little light draws the leaves out soft and floppy.
Water freely while the plant is in active growth and carrying leaves, always letting the mix approach dryness between waterings. As the leaves begin to yellow and drop in autumn, taper off and keep the plant nearly dry through its winter dormancy — a wet, cold, dormant caudex rots easily, which is the most common way these plants are lost. Many growers keep the caudex partly raised above the soil line for display, but young plants often establish faster grown a little deeper. See Repotting for handling; because the sap is a caustic irritant, wear gloves and avoid contact with eyes and skin when working with cut or damaged plants.
Propagation
Seed is the usual and most reliable method. While the genus as a whole is predominantly monoecious, many succulent euphorbias are dioecious (separate male and female plants); where that is the case, producing viable seed requires flowering plants of both sexes, and fresh seed sown on a warm, gritty surface germinates best. Clustered or offsetting plants can sometimes be divided, and cuttings may be taken, though rooting a caudex-forming species from cuttings is less dependable and any cut surface must be allowed to callus first. See Propagation - seed and Propagation - cuttings for general technique, and handle the latex-bleeding cuts with care.
Common problems
- Rot — the leading cause of loss, almost always from watering a dormant plant or from a slow-draining mix; the caudex softens and discolours.
- Etiolation — too little light stretches the leaves and loosens the tidy rosette.
- Pests — mealybugs (white fluff in the crown and among the leaf bases) and root mealybugs on the caudex are the usual offenders; see Pests and diseases.
See also
- Euphorbia — the genus overview
- Soil and potting mix · Watering · Repotting · Propagation - seed · Pests and diseases