Cold hardiness & minimum temperature

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

Also called Window haworthia, Cooper's haworthia pilifera.

More about cooper's haworthia (pilifera)

About Cooper's Haworthia (Pilifera)

Haworthia cooperi var. pilifera · also called Window haworthia, Cooper's haworthia pilifera · houseplant

Cooper's Haworthia pilifera is a small clustering succulent with plump, translucent blue-green leaves topped by fine bristle-like hairs and glassy 'windows' that let light into the buried tissue. It thrives in bright indirect light, needs deep but infrequent watering in gritty soil, and stays compact under 10 cm, ideal for sunny windowsills.

Cold limit: USDA 9-11 (indoor in most US homes) · RHS H1c (16-27°C)

What cooper's haworthia (pilifera)'s hardiness rating actually means

Cooper's Haworthia (Pilifera) 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 9-11 (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). Cooper's Haworthia (Pilifera) has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for cooper's haworthia (pilifera) 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 cooper's haworthia (pilifera) 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 cooper's haworthia (pilifera) can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

Cooper's Haworthia (Pilifera) hardiness — frequently asked questions

Is cooper's haworthia (pilifera) cold hardy?

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

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

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

What hardiness zone is cooper's haworthia (pilifera)?

Cooper's Haworthia (Pilifera) is rated USDA 9-11 (indoor in most US homes) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can cooper's haworthia (pilifera) 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 cooper's haworthia (pilifera) 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.