Cold hardiness & minimum temperature

Is Coral Cactus (Euphorbia lactea 'Cristata')cold hardy? Hardiness zone & min temp

Also called Coral cactus, Crested candelabra plant, Crested euphorbia, Crested elkhorn.

More about coral cactus

About Coral Cactus

Euphorbia lactea 'Cristata' · also called Coral cactus, Crested candelabra plant · houseplant

The coral cactus is not a true cactus but a grafted succulent: a fan-shaped, crested Euphorbia lactea crest joined onto a Euphorbia neriifolia rootstock. It wants bright indirect light, gritty fast-draining soil, and sparing water. Like all Euphorbia it bleeds an irritant latex sap and is toxic to pets and people.

Cold limit: USDA 10-11 (tender; grown indoors in cooler climates) (15-26C)

Watch for — Cold and frost damage: Tender and frost-sensitive. Sustained temperatures below about 10C (50F) cause damage, so keep it warm indoors and away from cold draughts and winter windowsills.

What coral cactus's hardiness rating actually means

Coral Cactus 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 H1c means: Warm-temperate — can summer outdoors but must come in well before the first frost. On the US scale that maps to USDA 10-11 (tender; grown indoors in cooler climates) — 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 5 °C (and never frost). Coral Cactus has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for coral cactus as it gets too cold:

Below about about 5 °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 coral cactus go outside or overwinter — and where?

It can holiday outdoors in summer once nights are reliably above 5 °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 coral cactus can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

Coral Cactus hardiness — frequently asked questions

Is coral cactus cold hardy?

Coral Cactus 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. Coral Cactus can only live outside year-round in genuinely frost-free climates (roughly USDA 10-11 (tender; grown indoors in cooler climates)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature coral cactus can survive?

Minimum survivable temperature is roughly about 5 °C (and never frost). Coral Cactus has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

What hardiness zone is coral cactus?

Coral Cactus is rated USDA 10-11 (tender; grown indoors in cooler climates) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can coral cactus survive winter outside?

It can holiday outdoors in summer once nights are reliably above 5 °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 coral cactus below its minimum temperature?

Below about about 5 °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.