Euphorbia milii
| Light | Full sun to bright light; the more light, the more flowers |
|---|---|
| Water | Regularly in growth, letting the top of the mix dry; sparingly in winter |
| Soil | Fast-draining, gritty mix (see Soil and potting mix) |
| Temperature | Warmth-loving; keep above about 10 °C, USDA zones 9b–11 |
| Propagation | Stem cuttings (primary); also seed |
| Toxicity | Toxic; the milky sap irritates skin and eyes and is poisonous if eaten — keep away from pets and children |
Euphorbia milii is a thorny, shrubby succulent from Madagascar, universally known as the crown of thorns. It is grown for its densely spined, sprawling stems and, above all, for the pairs of showy petal-like bracts — in shades of red, pink, salmon, white and yellow — that it can carry almost year-round, including the enormous blooms of the modern Thai and Poysean hybrids.
Description
Euphorbia milii forms a woody, branching shrub that in cultivation is usually kept to 30–90 cm but can sprawl larger with age. The grey-brown stems are ridged and armed with sharp, stiff spines, and carry bright green, spoon-shaped leaves toward their tips; older growth tends to shed its lower leaves and go bare, leaving the thorns exposed.
Like all euphorbias, the "flowers" are not what they seem. The true flowers are tiny and clustered in a specialised structure called a cyathium; what catches the eye is the pair of rounded, brightly coloured bracts beneath each cluster. These bracts are long-lasting and, given enough light and warmth, appear in flushes through much of the year. The plant bleeds a milky white latex when cut or broken — a hallmark of the genus and the source of its toxicity.
Distribution and habitat
The species is native to Madagascar, where it grows in seasonally dry, rocky and scrubby habitats. It has since become one of the most widely grown ornamental succulents in warm climates around the world, thriving outdoors in frost-free regions and as a windowsill or greenhouse plant everywhere else. A number of closely related Madagascan species and forms are traded under the same broad "crown of thorns" umbrella, and much of the material in cultivation is of hybrid origin.
Cultivation
Euphorbia milii is one of the easiest and most forgiving flowering succulents, tolerant of heat, drought and neglect. Give it the brightest spot you can — full sun outdoors or a south-facing window — as light is the single biggest factor in how freely it blooms. Grow it in a free-draining, gritty mix and water regularly through the warm growing season, letting the surface dry between waterings; cut back sharply in winter, keeping the plant on the dry side and above roughly 10 °C.
The stems are brittle and sharply spined, so handle with care and wear gloves — the sap is an irritant and should be kept off skin, eyes and mouth. Wash any sap off promptly. Pruning is well tolerated and encourages bushier, more floriferous growth; do it in the growing season and let cut surfaces callus. See Watering, Repotting and Pests and diseases for general technique.
Propagation
The usual method is stem cuttings. Take a cutting in warm weather, then dip or rinse the cut end to stop the flow of latex and allow it to dry and callus for several days before setting it in a gritty, barely-moist mix to root. Species plants also set seed, but named hybrids are kept true only by cuttings, since seed-raised plants vary. See Propagation — cuttings for a full walkthrough.
Cultivars
E. milii has been bred intensively, especially in Thailand, where growers have produced the large-flowered lines often sold as Thai hybrids or Poysean. These carry bracts several times the size of the wild form, in a huge range of colours and patterns — solids, bicolours and speckled types — and are prized as auspicious plants in parts of Southeast Asia. Compact, small-leaved dwarf forms and heavy-blooming pot types are also common in the trade.
Common problems
- Leaf drop — some shedding of lower leaves is natural, but sudden heavy drop usually signals cold, drought stress, or a big change in light.
- Poor flowering — almost always too little light; move the plant somewhere brighter.
- Rot — from overwatering or a poorly draining mix, especially in a cool, wet winter; the base or stems go soft and brown.
- Pests — mealybugs (white fluff in the joints) and spider mites are the most frequent visitors.
See also
- Euphorbia — the genus overview
- Propagation — cuttings · Soil and potting mix · Watering · Repotting · Pests and diseases