Pencil Cactus
Euphorbia tirucalli
Through the year 🗓️
☀️ Summer now
Full sun and sparing water. This is when 'Sticks on Fire' earns its name.
🍂 Fall
Taper watering as light fades and stop fertilizing.
❄️ Winter
Water about monthly, keep it above 50 °F and give it your sunniest window to hold its color.
🌱 Spring
Prune for shape early in the season (gloves, glasses, rinsed blades) and resume light feeding.
The details
Light & placement
- Light
- Full sun to very bright light; the more direct sun, the better
- Ideal PPFD
- 400–800 µmol·m⁻²·s⁻¹
- Grow-light distance
- 6–12 in below LED
Water & feed
- Watering method
- Soak-and-dry: water deeply, then let the soil dry out completely; it shrugs off drought far better than damp. In winter, once a month is plenty.
- Fertilizer
- Cactus/succulent feed at ½ strength, ~every 4–6 wks in spring–summer; none in winter.
Home & habit
- Soil
- Gritty, sharply draining cactus/succulent mix; pH 6.0–7.5
- Humidity
- Low; loves dry air (30–40%)
- Temperature
- 65–90 °F; keep above 50 °F
- Mature size
- 4–8 ft indoors (30 ft in habitat)
- Repotting
- Every 2–3 yrs into a heavy pot; wear gloves, since roots and stems both bleed sap
- Propagation
- Pencil-thick cuttings: rinse the flowing sap in cool water, callus ~1 wk, pot in dry mix. Gloves and eye protection are non-negotiable.
When something looks wrong
- Overwatering signs
- Yellowing, mushy stems; branch dieback; rot at the soil line
- Underwatering signs
- Wrinkled, dull, greying stems (it takes a long drought to get here)
- Common pests
- Mealybugs, spider mites, scale (all uncommon)
Common problems 🩺
The usual suspects when Pencil Cactus looks unhappy. Most houseplant trouble is watering or light, not disease — see all plant problems if you are not sure which plant is the culprit.
Yellowing, soft stems near the base
Likely cause
Overwatering.
What to do
Let it dry out completely between waterings and use gritty mix. Wear gloves and eye protection when pruning — the white sap is a serious irritant.
Thin, floppy, pale stems
Likely cause
Not enough light.
What to do
Give it as much direct sun as you can; it firms up and colors in strong light.
Dropping its tiny leaves
Likely cause
Normal. The small leaves are temporary and shed routinely.
What to do
No action needed — the green stems do the photosynthesis.
More like this 🌿
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