Cold hardiness & minimum temperature

Is Caralluma speciosa (Caralluma speciosa)cold hardy? Hardiness zone & min temp

Also called showy caralluma.

More about caralluma speciosa

About Caralluma speciosa

Caralluma speciosa · also called showy caralluma · houseplant

Caralluma speciosa is a larger East African stapeliad succulent with robust, upright four-angled grey-green stems and clusters of showy, star-shaped purple-brown carrion flowers. It is a striking specimen plant needing strong sun, very gritty soil, and careful, sparing watering. Treat it like a desert succulent and keep it nearly dry through its cool winter rest.

Cold limit: USDA 10-11 (indoor in most US homes) · RHS H1c (18-32C)

Watch for — Basal stem rot: The thicker stems hold water and rot readily if overwatered or kept cold and damp. Remove affected tissue and re-root clean cuttings in dry gritty mix.

What caralluma speciosa's hardiness rating actually means

Caralluma speciosa 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 (indoor in most US homes) — 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). Caralluma speciosa has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for caralluma speciosa 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 caralluma speciosa 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 caralluma speciosa can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

Caralluma speciosa hardiness — frequently asked questions

Is caralluma speciosa cold hardy?

Caralluma speciosa 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. Caralluma speciosa can only live outside year-round in genuinely frost-free climates (roughly USDA 10-11 (indoor in most US homes)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature caralluma speciosa can survive?

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

What hardiness zone is caralluma speciosa?

Caralluma speciosa is rated USDA 10-11 (indoor in most US homes) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can caralluma speciosa 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 caralluma speciosa 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.