Cold hardiness & minimum temperature

Is large-flowered butterwort (Pinguicula grandiflora)cold hardy? Hardiness zone & min temp

Also called large-flowered butterwort, greater butterwort.

More about large-flowered butterwort

About large-flowered butterwort

Pinguicula grandiflora · also called large-flowered butterwort, greater butterwort · houseplant

A cold-hardy European carnivorous perennial native to the limestone mountains of Ireland, western France, and northern Spain, Pinguicula grandiflora produces showy violet-blue flowers up to 2.5 cm across in late spring. It forms winter hibernacula and tolerates hard frost, making it one of the few butterworts suited to outdoor temperate gardens.

Cold limit: USDA 5-8 · RHS H6 (2–18°C growing season; tolerates −15°C in winter dormancy)

Watch for — Failure to flower or form hibernacula: This species absolutely requires a cool-cold winter rest (temperatures 2–8°C for 8–12 weeks). Without it, kept warm indoors year-round, plants weaken and cease flowering. Move outdoors or to an unheated greenhouse from October through February.

What large-flowered butterwort's hardiness rating actually means

Yes — large-flowered butterwort is genuinely cold hardy. Rated RHS H6 and USDA 5-8, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H6 means: Hardy throughout the UK and northern Europe. On the US scale that maps to USDA 5-8 — 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 −20 to −15 °C. large-flowered butterwort is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for large-flowered butterwort as it gets too cold:

It tolerates winter lows to about −20 to −15 °C once established.
Below its rated zone, the visible damage is browned or blackened top growth and, in the worst case, a killed crown or root.
First-year, newly planted, or container-grown specimens are noticeably less hardy than established garden plants — the roots are exposed.

Can large-flowered butterwort go outside or overwinter — and where?

Plant it out within USDA 5-8 and it overwinters with little or no help.
It does not want to come indoors — a warm winter room actually weakens a hardy plant by denying it dormancy.
The real risks in its range are waterlogging, wind-rock on young plants, and a late hard frost on new growth — not ordinary winter cold.

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 large-flowered butterwort can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

large-flowered butterwort hardiness — frequently asked questions

Is large-flowered butterwort cold hardy?

Yes — large-flowered butterwort is genuinely cold hardy. Rated RHS H6 and USDA 5-8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. large-flowered butterwort is hardy across USDA 5-8; it belongs in the ground or a frost-proof container, not on a windowsill, and many types actively need a cold winter to perform.

What is the minimum temperature large-flowered butterwort can survive?

Minimum survivable temperature is roughly about −20 to −15 °C. large-flowered butterwort is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is large-flowered butterwort?

large-flowered butterwort is rated USDA 5-8 and RHS H6 — Hardy throughout the UK and northern Europe.

Can large-flowered butterwort survive winter outside?

Plant it out within USDA 5-8 and it overwinters with little or no help. It does not want to come indoors — a warm winter room actually weakens a hardy plant by denying it dormancy. The real risks in its range are waterlogging, wind-rock on young plants, and a late hard frost on new growth — not ordinary winter cold.

What happens to large-flowered butterwort below its minimum temperature?

It tolerates winter lows to about −20 to −15 °C once established. Below its rated zone, the visible damage is browned or blackened top growth and, in the worst case, a killed crown or root. First-year, newly planted, or container-grown specimens are noticeably less hardy than established garden plants — the roots are exposed.