Cold hardiness & minimum temperature

Is Moctezuma Butterwort (Pinguicula moctezumae)cold hardy? Hardiness zone & min temp

Also called Moctezuma butterwort, Mexican butterwort.

More about moctezuma butterwort

About Moctezuma Butterwort

Pinguicula moctezumae · also called Moctezuma butterwort, Mexican butterwort · houseplant

Pinguicula moctezumae is a rare carnivorous butterwort found exclusively in a narrow sub-canyon of the Rio Moctezuma on the Hidalgo-Queretaro border in Mexico, where it clings to wet limestone and tufa walls at 900-1,100 m altitude. It is recognised by its exceptionally long, narrow, strap-like leaves and is prized in cultivation for its prolific, rich pink flowers. Like other Mexican Pinguicula it is heterophyllous, with summer carnivorous leaves and compact winter succulent leaves — water must be nearly withheld in winter. 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 (10-28°C)

Watch for — Root rot from winter overwatering: The succulent winter form is highly susceptible to rot if the substrate remains wet. Transition to near-dry conditions immediately when the plant begins forming its compact winter leaves, and ensure the pot never sits in a water tray during this period.

What moctezuma butterwort's hardiness rating actually means

Moctezuma 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). Moctezuma Butterwort has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Moctezuma Butterwort hardiness — frequently asked questions

Is moctezuma butterwort cold hardy?

Moctezuma 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. Moctezuma 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 moctezuma butterwort can survive?

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

What hardiness zone is moctezuma butterwort?

Moctezuma 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 moctezuma 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 moctezuma 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.