Cold hardiness & minimum temperature

Is Pencil Cactus (Firestick) (Euphorbia tirucalli)cold hardy? Hardiness zone & min temp

Also called Pencil cactus, Firestick, Sticks on fire, Milkbush, Pencil tree, Indian tree spurge, Aveloz.

More about pencil cactus (firestick)

About Pencil Cactus (Firestick)

Euphorbia tirucalli · also called Pencil cactus, Firestick · houseplant

Pencil cactus (Euphorbia tirucalli), also sold as Firestick, is a slow-growing succulent shrub with slim, pencil-like stems that flush orange-red in bright light and cool temps. Give it lots of sun, gritty soil, and infrequent water. ASPCA-listed toxic to cats, dogs, and horses; its milky sap also burns skin and eyes.

Cold limit: USDA 11-12 (survives in zone 10 in frost-free areas of California and southern Florida) (18-27°C (tolerates down to about 10°C); keep above 4-5°C)

Watch for — Loss of red/orange colour: The fiery tips fade in low light or constant warmth. Bright direct sun plus cooler autumn-winter temperatures bring the colour back; it greens up again in shade or summer heat.

What pencil cactus (firestick)'s hardiness rating actually means

Pencil Cactus (Firestick) is not cold hardy. It is a tropical houseplant that dies if it is left out through frost — there is no zone where it overwinters outdoors in a UK or cold-US climate. Its RHS rating of H1b means: Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season. On the US scale that maps to USDA 11-12 (survives in zone 10 in frost-free areas of California and southern Florida) — the zones where it can be left outdoors year-round.

New to these scales? The USDA hardiness zone map explained covers how the zone numbers work, and you can find your own zone with the zone finder.

Minimum temperature — and what happens below it

Minimum survivable temperature is roughly about 10 °C (sustained cold below this is damaging). Pencil Cactus (Firestick) has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for pencil cactus (firestick) as it gets too cold:

Below about about 10 °C, growth stalls and the leaves start to show cold stress — dark, water-soaked, or yellowing patches.
A single light frost blackens the foliage; a hard freeze kills the whole plant, roots included, and it does not recover.
Even a cold, draughty windowsill or an unheated porch in winter can be enough to damage it permanently.

Can pencil cactus (firestick) go outside or overwinter — and where?

It can holiday outdoors in summer once nights are reliably above 10 °C, in shade or dappled light, hardened off gradually.
Bring it back indoors well before the first autumn frost — do not wait for a frost warning, move it when nights drop toward 10-12 °C.
It will never overwinter outside in a temperate climate; the indoors is its winter home, full stop.

Work back from your local frost dates with the frost-date calculator: the last spring frost and first autumn frost are what really decide when pencil cactus (firestick) can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1b figure above.

Pencil Cactus (Firestick) hardiness — frequently asked questions

Is pencil cactus (firestick) cold hardy?

Pencil Cactus (Firestick) is not cold hardy. It is a tropical houseplant that dies if it is left out through frost — there is no zone where it overwinters outdoors in a UK or cold-US climate. Indoor-only in almost every home. Pencil Cactus (Firestick) can only live outside year-round in genuinely frost-free climates (roughly USDA 11-12 (survives in zone 10 in frost-free areas of California and southern Florida)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature pencil cactus (firestick) can survive?

What hardiness zone is pencil cactus (firestick)?

Pencil Cactus (Firestick) is rated USDA 11-12 (survives in zone 10 in frost-free areas of California and southern Florida) and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can pencil cactus (firestick) survive winter outside?

It can holiday outdoors in summer once nights are reliably above 10 °C, in shade or dappled light, hardened off gradually. Bring it back indoors well before the first autumn frost — do not wait for a frost warning, move it when nights drop toward 10-12 °C. It will never overwinter outside in a temperate climate; the indoors is its winter home, full stop.

What happens to pencil cactus (firestick) below its minimum temperature?

Below about about 10 °C, growth stalls and the leaves start to show cold stress — dark, water-soaked, or yellowing patches. A single light frost blackens the foliage; a hard freeze kills the whole plant, roots included, and it does not recover. Even a cold, draughty windowsill or an unheated porch in winter can be enough to damage it permanently.