Cold hardiness & minimum temperature

Is Alpine Mouse-ear (Cerastium alpinum)cold hardy? Hardiness zone & min temp

Also called Alpine Mouse-ear, Alpine Chickweed.

More about alpine mouse-ear

About Alpine Mouse-ear

Cerastium alpinum · also called Alpine Mouse-ear, Alpine Chickweed · flowering

A delicate, cushion-forming perennial native to Arctic and alpine zones across the Northern Hemisphere, including mountain ranges of Europe and North America. Produces small, pristine white flowers with notched petals above a compact mat of hairy, grey-green leaves in late spring. Best suited to troughs, alpine houses, or specialist rock gardens requiring excellent drainage.

Cold limit: USDA 2–6 · RHS H7 (-40 to 18°C)

Watch for — Winter rot in wet conditions: The primary cultivation challenge. In areas with wet winters, grow under glass in an alpine house or cold frame, or ensure a gravel collar and sharp overhead drainage. A pane of glass over plants outdoors can be sufficient protection in maritime climates.

What alpine mouse-ear's hardiness rating actually means

Yes — alpine mouse-ear is genuinely cold hardy. Rated RHS H7 and USDA 2–6, 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 2–6 — 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. Alpine Mouse-ear is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for alpine mouse-ear 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 alpine mouse-ear go outside or overwinter — and where?

Plant it out within USDA 2–6 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 alpine mouse-ear can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Alpine Mouse-ear hardiness — frequently asked questions

Is alpine mouse-ear cold hardy?

Yes — alpine mouse-ear is genuinely cold hardy. Rated RHS H7 and USDA 2–6, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Alpine Mouse-ear is hardy across USDA 2–6; 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 alpine mouse-ear can survive?

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

What hardiness zone is alpine mouse-ear?

Alpine Mouse-ear is rated USDA 2–6 and RHS H7 — Hardy in the severest European continental winters.

Can alpine mouse-ear survive winter outside?

Plant it out within USDA 2–6 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 alpine mouse-ear 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.