Cold hardiness & minimum temperature

Is Alpine Balsam (Erinus alpinus)cold hardy? Hardiness zone & min temp

Also called Alpine Balsam, Fairy Foxglove, Alpine Liver Balsam.

More about alpine balsam

About Alpine Balsam

Erinus alpinus · also called Alpine Balsam, Fairy Foxglove · flowering

Alpine Balsam is a charming, short-lived perennial or biennial native to mountain crevices in the Pyrenees and Alps. It produces a profusion of small, bright pink to purple five-petalled flowers from late spring to early summer. Perfect for planting in wall crevices, rock gardens, and paving gaps, it self-seeds freely in suitable spots.

Cold limit: USDA 4–8 · RHS H6 (-15 to 22°C)

What alpine balsam's hardiness rating actually means

Yes — alpine balsam is genuinely cold hardy. Rated RHS H6 and USDA 4–8, 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 4–8 — 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. Alpine Balsam is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for alpine balsam 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 alpine balsam go outside or overwinter — and where?

Plant it out within USDA 4–8 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 alpine balsam can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Alpine Balsam hardiness — frequently asked questions

Is alpine balsam cold hardy?

Yes — alpine balsam is genuinely cold hardy. Rated RHS H6 and USDA 4–8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Alpine Balsam is hardy across USDA 4–8; 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 alpine balsam can survive?

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

What hardiness zone is alpine balsam?

Alpine Balsam is rated USDA 4–8 and RHS H6 — Hardy throughout the UK and northern Europe.

Can alpine balsam survive winter outside?

Plant it out within USDA 4–8 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 alpine balsam 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.