Cold hardiness & minimum temperature

Is Alpine Bartsia (Bartsia alpina)cold hardy? Hardiness zone & min temp

Also called Alpine Bartsia, Velvetbells.

More about alpine bartsia

About Alpine Bartsia

Bartsia alpina · also called Alpine Bartsia, Velvetbells · flowering

Bartsia alpina is a rare, low-growing hemiparasitic perennial native to alpine and subalpine calcareous grasslands, flushes, and snow-bed communities across Arctic and mountain Europe, with very restricted populations in northern England and Scotland. As a hemiparasite, it photosynthesises but also obtains water and nutrients by attaching to the roots of neighbouring host plants such as sedges and grasses, and is extremely difficult to cultivate without them. Its deep purple-violet flowers are produced on woolly stems in summer. Toxicity to pets has not been established in the ASPCA database; treat with caution.

Cold limit: USDA 3-6 · RHS H7 (-25 to 18°C)

What alpine bartsia's hardiness rating actually means

Yes — alpine bartsia is genuinely cold hardy. Rated RHS H7 and USDA 3-6, 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 3-6 — 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 Bartsia is built for winter — once established it takes hard frost and snow in its stride.

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

Plant it out within USDA 3-6 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 bartsia can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Alpine Bartsia hardiness — frequently asked questions

Is alpine bartsia cold hardy?

Yes — alpine bartsia is genuinely cold hardy. Rated RHS H7 and USDA 3-6, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Alpine Bartsia is hardy across USDA 3-6; 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 bartsia can survive?

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

What hardiness zone is alpine bartsia?

Alpine Bartsia is rated USDA 3-6 and RHS H7 — Hardy in the severest European continental winters.

Can alpine bartsia survive winter outside?

Plant it out within USDA 3-6 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 bartsia 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.