Pencil Cactus
Euphorbia tirucalli · Firesticks
It looks like a coral firework of green pencil-thick stems, but it is not a cactus at all. It is an African spurge, and the milky sap inside is its real story: a caustic latex that burns skin and can blind on eye contact.
Family
Euphorbiaceae
Origin
Eastern Africa
In the wild
A tree to 9 m
Indoors
0.6–1.8 m
Growth
Moderate to fast
With pets
Toxic, caustic sap
Where it's from
Eastern and southern Africa
African dryland tree
From semi-arid eastern and southern Africa, carried along old trade routes until it grew pantropical.
A tree to 9 m
In habitat it reaches around 7 to 9 m, a dense thicket of pencil-thick stems.
Outdoors: zones 11–12
Frost-tender. A dryland hedge and windbreak in warm regions, a houseplant everywhere colder.
Not a cactus, and the sap can blind you
It is a stem-succulent Euphorbia, not a cactus, and its leaves are tiny and drop early so the green stems do the photosynthesis. Inside runs a milky latex that is corrosive and severely irritating: it burns skin and mouth and can cause temporary blindness if it reaches the eyes. Always handle it with gloves and eye protection.
It bleeds when cut
Cuttings pour out white latex, the same sap that propagates it easily and can blind on contact.
Once pitched as a fuel crop
A Nobel-winning chemist proposed extracting its hydrocarbon-rich latex as a renewable oil crop.
A cautionary remedy
Used in folk medicine, but studies link the latex to immune suppression and a co-factor in Burkitt's lymphoma. Not a safe home remedy.
How to keep it
LightFull sun
Strong direct light brings out the fire colour in 'Firesticks'. It greens up in shade.
WaterSoak then dry fully
Dry to medium. Soak, then let it dry out completely. Minimal in winter; overwatering is the main killer.
HumidityLow is fineTolerates dry indoor air with no misting. It came from the dryland.
TemperatureWarm, frost-freeNot frost-hardy. Protect it from cold below about 0 to 4°C.
SoilGritty, fast-drainingA low-organic cactus or succulent mix. Never heavy or water-retentive.
FeedingLight, in summerA light feed in the growing season only. Succulents need little.
DifficultyEasy to growForgiving and drought-proof, but the toxic sap makes handling the real challenge.
With petsToxic, caustic sapIrritant latex. Mouth and stomach irritation and vomiting if chewed, plus a serious skin and eye hazard.
PropagationStem cuttingsCut a stem, rinse and blot the latex, let it callus for several days, then root in dry mix. Gloves and goggles on.
RepottingEvery 2–3 yearsWhen rootbound. Always with gloves and eye protection.
What the data says
What it costs
Inexpensive and mass-propagated from cuttings. No collector bubble here.
$8–80
Small 'Firesticks' pots run cheapest; large multi-stem specimens cost more. The colour intensifies in full sun and cool weather.
IUCN · Least Concern
In the wild
A rare win-win: abundant in the wild and mass-cultivated everywhere. If anything, it spreads too well.
Assessed Least Concern in 2017, present across the world's tropics and common throughout its range. Drought, salt and wind tolerant, it naturalises easily and can become weedy where introduced. Like most succulent Euphorbia, it is listed on CITES Appendix II, though plants in trade are propagated, not wild-collected.
When it sulks
Mushy, blackening stemsRoot rot from overwatering or poor drainage. The number one killer.
No fire colourToo little light. 'Firesticks' needs strong direct sun and cool, dry conditions to colour up.
Shrivelled, wrinkled stemsSevere underwatering, rare for a succulent, or root damage.
Sap on skin or in eyesNot a plant problem but the top hazard. Rinse immediately, especially the eyes, and seek help.
PestsSpider mites, aphids and mealybugs. Check and treat early.
Varieties & company
The varieties
Sticks on FireFiresticksRoseaGreen wild form
Pairs with · keep apart from
AloeAgaveSnake PlantMonsteraFernsPeace Lily
A new plant, every week.
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