Cold hardiness & minimum temperature

Is Cooper's Haworthia (Haworthia cooperi)cold hardy? Hardiness zone & min temp

Also called Cooper's Haworthia, Window Haworthia, Pussy Foot, Cushion Aloe, Bristle Haworthia.

More about cooper's haworthia

About Cooper's Haworthia

Haworthia cooperi · also called Cooper's Haworthia, Window Haworthia · houseplant

Cooper's Haworthia is a tiny, slow-growing South African succulent forming clumps of plump rosettes with translucent "windowed" leaf tips. Give it bright indirect light, gritty fast-draining soil, and infrequent deep watering. It is ASPCA-listed as non-toxic to cats and dogs, making it a safe, low-fuss choice for pet households.

Cold limit: USDA USDA 9b-11 (frost-free climates only; grow as a houseplant elsewhere) (18-27°C)

Watch for — Translucent, mushy or rotting leaves: The most common issue, caused by overwatering or soil that stays wet. Let the mix dry fully between waterings, use a gritty fast-draining medium and a pot with drainage, and cut back hard in winter.

What cooper's haworthia's hardiness rating actually means

Cooper's Haworthia 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 USDA 9b-11 (frost-free climates only; grow as a houseplant elsewhere) — 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). Cooper's Haworthia has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for cooper's haworthia 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 cooper's haworthia 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 cooper's haworthia can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1b figure above.

Cooper's Haworthia hardiness — frequently asked questions

Is cooper's haworthia cold hardy?

Cooper's Haworthia 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. Cooper's Haworthia can only live outside year-round in genuinely frost-free climates (roughly USDA USDA 9b-11 (frost-free climates only; grow as a houseplant elsewhere)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature cooper's haworthia can survive?

What hardiness zone is cooper's haworthia?

Cooper's Haworthia is rated USDA USDA 9b-11 (frost-free climates only; grow as a houseplant elsewhere) and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can cooper's haworthia 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 cooper's haworthia 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.