Cold hardiness & minimum temperature

Is Variable-Leaved Butterwort (Pinguicula heterophylla)cold hardy? Hardiness zone & min temp

Also called Variable-leaved butterwort, Mexican butterwort.

More about variable-leaved butterwort

About Variable-Leaved Butterwort

Pinguicula heterophylla · also called Variable-leaved butterwort, Mexican butterwort · houseplant

Pinguicula heterophylla is a carnivorous butterwort endemic to the Mexican states of Morelos, Guerrero, and Oaxaca, where it grows in mountainous terrain. Its common and species names refer to its striking dimorphic leaves — tall, upright, narrow carnivorous leaves in summer that resemble threadleaf sundews, contrasting with a compact subterranean onion-like bulb in winter — the single most important care fact is that this bulb must be kept completely bone-dry during winter dormancy or it will rot within days. It is not confirmed as non-toxic on the ASPCA database and carries a precautionary mildly-toxic rating.

Cold limit: USDA 10-12 (indoor in most climates) · RHS H1c (13-29°C)

Watch for — Bulb rot during winter dormancy: Any moisture reaching the dormant bulb — even high ambient humidity — can cause rapid rot. Remove from the tray immediately when leaves begin to die back, store in a dry spot, and do not water at all until new leaf tips emerge in spring.

What variable-leaved butterwort's hardiness rating actually means

Variable-Leaved Butterwort 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 10-12 (indoor in most 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). Variable-Leaved Butterwort has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Variable-Leaved Butterwort hardiness — frequently asked questions

Is variable-leaved butterwort cold hardy?

Variable-Leaved Butterwort 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. Variable-Leaved Butterwort can only live outside year-round in genuinely frost-free climates (roughly USDA 10-12 (indoor in most climates)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature variable-leaved butterwort can survive?

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

What hardiness zone is variable-leaved butterwort?

Variable-Leaved Butterwort is rated USDA 10-12 (indoor in most climates) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can variable-leaved butterwort 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 variable-leaved butterwort 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.