Pencil cactus (Euphorbia tirucalli) care

Succulents & cacti · easy to keep

Pencil cactus (Euphorbia tirucalli) wants bright light with direct sun. Water it every 2 weeks. Water thoroughly, then leave it until the pot is bone dry and the lower leaves have gone slightly soft. Never water into the rosette — water sitting in the centre rots it. Pot it in gritty cactus compost, at least half grit or perlite. A weak cactus feed two or three times over the summer, and repot every 2 years. Humidity: indifferent; dry air is ideal. Toxic to cats, dogs and people, and the most genuinely hazardous plant in the house.

Pencil cactus, or firesticks: a tangle of smooth green pencil-thick stems with almost no leaves, turning coral-orange in strong sun and cold. Also not a cactus, and carrying the same dangerous latex as its milk-tree relative — this is the plant to be most careful with in the house.

Quick facts

Water: Water every 2 weeks. Water thoroughly, then leave it until the pot is bone dry and the lower leaves have gone slightly soft. Never water into the rosette — water sitting in the centre rots it.
Light: Bright light with direct sun.
Humidity: Indifferent; dry air is ideal.
Soil: Gritty cactus compost, at least half grit or perlite.
Feeding: A weak cactus feed two or three times over the summer.
Repotting: Repot every 2 years.
Toxic to pets: Toxic to cats, dogs and people, and the most genuinely hazardous plant in the house. The white latex burns skin and can cause lasting damage to eyes — wear gloves and eye protection when cutting one, and wash immediately if it touches you.
Difficulty: Easy.
Mature size: 1–2 m indoors.
Native to: Eastern and southern Africa.

Watering a Pencil cactus

Water every 2 weeks. Water thoroughly, then leave it until the pot is bone dry and the lower leaves have gone slightly soft. Never water into the rosette — water sitting in the centre rots it.

That cadence is the one PlantParlour sets for this species when you name it, and it is deliberately on the cautious side — a plant that asks a day early is safer than one that asks a day late. Log each watering and the reminder moves with the plant rather than with the calendar.

Light

As much direct sun as you can give it — four to six hours minimum. An echeveria in a normal room stretches into a pale tower within weeks, and no amount of later light will make it compact again.

Humidity and temperature

Indifferent; dry air is ideal. Central heating in winter is what turns a comfortable room into a dry one, and it is the usual reason an established plant suddenly browns at the edges or picks up spider mites.

Soil and potting

Cactus compost cut with more grit. A terracotta pot helps because it wicks water out of the mix and away from the roots.

Feeding

A weak cactus feed two or three times over the summer. Stop feeding in autumn and start again when you see new growth in spring — feeding a plant that isn't growing just builds up salts in the pot.

Repotting

Repot every 2 years. Every two or three years in spring, into a pot barely larger than the rosette.

Common problems

Stretched, pale, spaced-out leaves
Not enough light. This is not reversible.

Fix: Cut the head off, let it callus for a few days, and re-root it in full sun. The stump usually produces offsets.
Mushy translucent lower leaves
Overwatering.

Fix: Stop watering. Remove the affected leaves and let it dry out completely.
Shrivelled wrinkled leaves
Genuinely thirsty.

Fix: Water thoroughly and it plumps back up within a day or two.
White cottony blobs between the leaves
Mealybugs.

Fix: Alcohol on a cotton bud, every few days for a month — they hide deep in the rosette.

Propagation

Stem cuttings, wearing gloves. Dip the cut end in water to stop the latex, let it callus for several days, then root in dry gritty mix.

A cutting taken in PlantParlour keeps its link to the plant it came from, so a propagation years later still traces back to the mother plant — which is the point if you ever sell or trade it.

Toxicity and safety

Toxic to cats, dogs and people, and the most genuinely hazardous plant in the house. The white latex burns skin and can cause lasting damage to eyes — wear gloves and eye protection when cutting one, and wash immediately if it touches you.

Questions people ask

How often should you water a Pencil cactus?

Water every 2 weeks as a starting point — that is the cadence PlantParlour sets for Euphorbia tirucalli. Water thoroughly, then leave it until the pot is bone dry and the lower leaves have gone slightly soft. Never water into the rosette — water sitting in the centre rots it. Light, pot size and the time of year all move that number, so treat it as a reminder to go and check rather than a rule.

How much light does a Pencil cactus need?