Euphorbia tirucalli
| Light | Bright light to full sun; brightest light brings out red tips on 'Firesticks' |
|---|---|
| Water | Sparingly; let the mix dry fully between waterings, near-dry in winter |
| Soil | Fast-draining mineral mix (see Soil and potting mix) |
| Temperature | Keep above about 10 °C; USDA zones 10–11 |
| Propagation | Stem cuttings (primary); seed |
| Toxicity | Toxic; the milky latex is a severe skin, eye and mucous-membrane irritant (see Pests and diseases and cautions below) |
Euphorbia tirucalli is a nearly leafless, pencil-stemmed tree succulent from Africa, widely grown as a houseplant and landscape plant and best known in the fiery orange-tipped selection 'Firesticks'. Its common name pencil cactus comes from the dense mass of slender, cylindrical green branches; despite the name it is a true euphorbia and not a cactus at all. Like all members of the genus, every part of the plant bleeds a copious white latex when cut.
Description
Euphorbia tirucalli is a large, shrubby to tree-like succulent that can reach several metres tall in the ground, forming a rounded crown of many-branched, pencil-thick green stems. The stems are smooth, cylindrical and spineless, branching repeatedly into a coral-like tangle. Photosynthesis happens almost entirely in these green stems: true leaves are tiny, narrow and short-lived, appearing near the growing tips and dropping quickly, so mature plants usually look completely leafless.
The flowers are inconspicuous — small yellowish structures (technically cyathia, the specialised euphorbia false-flower) clustered at the branch tips — and are of little ornamental note. The plant's appeal lies entirely in its architectural, almost otherworldly branching habit.
Distribution and habitat
The species is native to a broad swathe of Africa, from the semi-arid regions of the east and northeast down through the drier parts of the continent, and it has long been cultivated and naturalised across the tropics and subtropics worldwide. It thrives in hot, dry, open country and tolerates poor soils, making it a common hedge, fence and boundary plant in warm climates. In frost-free regions it can become large and even weedy where conditions suit it.
Cultivation
Euphorbia tirucalli is an easy, fast, forgiving grower given warmth and light. Plant it in a very free-draining, mostly mineral mix and give it as much light as you can — bright light keeps the stems compact, and the orange 'Firesticks' selection needs strong sun to develop and hold its warm colouring. Water thoroughly once the mix has dried out, then let it dry again; ease right off through the cool, short days of winter to prevent rot.
It is sensitive to cold and will be damaged or killed by frost, so grow it under cover or indoors where winters are cold, keeping it above roughly 10 °C. Indoors, a bright window and a snug pot suit it well. See Watering and Repotting for general technique.
Cautions with the latex
This is the one plant in a beginner's collection that genuinely warrants care in handling. Every cut or broken stem oozes a white latex that is a serious irritant: on skin it can cause burning and blistering, and contact with the eyes can cause intense pain and even temporary or lasting eye damage. Always wear gloves and eye protection when pruning or taking cuttings, keep the sap away from your face, wash any splashes off promptly, and keep the plant out of reach of children and pets. Never handle it and then rub your eyes. Because of this, many growers site it away from busy walkways and high-traffic indoor spots.
Propagation
Propagation is easy from stem cuttings. Cut a length of stem (wearing gloves and eye protection), then stop the flow of latex by dipping or rinsing the cut end in water, or letting it callus for several days in a dry, airy spot. Once callused, set the cutting in a dry, gritty mix and water only sparingly until roots form. The species can also be grown from seed, though cuttings are far quicker and are how named selections such as 'Firesticks' are kept true.
Cultivars
The dominant selection in cultivation is E. tirucalli 'Firesticks (also sold as Sticks on Fire), a form whose young stems flush warm shades of yellow, orange and coral red, deepening to fiery red in bright sun and cool weather and softening to yellow-green in shade or heavy shade. Its care is exactly as for the species. Because the colour is light-driven, a 'Firesticks' grown too dark will revert to plain green until moved back into stronger light.
Common problems
- Rot — the usual cause of loss, almost always from overwatering, a slow-draining mix, or cold wet conditions; stems soften, discolour and collapse.
- Loss of colour — 'Firesticks' fading to green signals too little light; move it somewhere brighter.
- Cold damage — frost or prolonged cold blackens and kills stems; protect from freezing.
- Pests — mealybugs (white fluff in the branch crotches) are the most common; see Pests and diseases.
See also
- Euphorbia — the genus overview
- Propagation — cuttings · Soil and potting mix · Watering · Repotting · Pests and diseases