Cold hardiness & minimum temperature

Is Common Butterwort (Pinguicula vulgaris)cold hardy? Hardiness zone & min temp

Also called Bog violet.

More about common butterwort

About Common Butterwort

Pinguicula vulgaris · also called Bog violet · flowering

Pinguicula vulgaris is a cold-hardy temperate butterwort of wet, alkaline-to-neutral fens and bogs across northern Europe, Asia, and North America. Its flat rosette of yellow-green, sticky leaves traps tiny insects and it bears solitary violet flowers in spring. It forms a winter resting bud and requires a genuine cold dormancy and permanently wet ground.

Cold limit: USDA 3-8 · RHS H7 (-20-25°C)

Watch for — Rot over winter: The dormant hibernaculum rots if kept flooded. Keep it just damp and cool over winter, not standing in deep water.

What common butterwort's hardiness rating actually means

Yes — common butterwort is genuinely cold hardy. Rated RHS H7 and USDA 3-8, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H7 means: Hardy in the severest European continental winters. On the US scale that maps to USDA 3-8 — 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 below about −20 °C. Common Butterwort is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for common butterwort as it gets too cold:

It tolerates winter lows to about −20 °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 common butterwort go outside or overwinter — and where?

Plant it out within USDA 3-8 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 common butterwort can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Common Butterwort hardiness — frequently asked questions

Is common butterwort cold hardy?

Yes — common butterwort is genuinely cold hardy. Rated RHS H7 and USDA 3-8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Common Butterwort is hardy across USDA 3-8; 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 common butterwort can survive?

Minimum survivable temperature is roughly below about −20 °C. Common Butterwort is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is common butterwort?

Common Butterwort is rated USDA 3-8 and RHS H7 — Hardy in the severest European continental winters.

Can common butterwort survive winter outside?

Plant it out within USDA 3-8 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 common butterwort below its minimum temperature?

It tolerates winter lows to about −20 °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.