Cold hardiness & minimum temperature

Is Arctic Bell-heather (Cassiope tetragona)cold hardy? Hardiness zone & min temp

Also called Arctic Bell-heather, White Arctic Mountain Heather, Four-angled Cassiope, White Mountainheath.

More about arctic bell-heather

About Arctic Bell-heather

Cassiope tetragona · also called Arctic Bell-heather, White Arctic Mountain Heather · flowering

Cassiope tetragona is a circumpolar arctic and subarctic dwarf evergreen shrub that forms dense low mats across tundra, rocky slopes, and snowbed communities from Alaska and northern Canada across Greenland, Svalbard, Scandinavia, Siberia, and into alpine zones of central Asia. Its upright wiry stems are clothed in four ranks of small, scale-like dark green leaves, producing solitary nodding white bell-shaped flowers in late spring to early summer. The most important care fact is that it demands a permanently moist, acid, peaty root run and absolutely must not experience drought or alkaline soil conditions. It is not listed on the ASPCA database but as an Ericaceae member should be treated as mildly toxic to pets.

Cold limit: USDA 1-4 · RHS H7 (-45°C to 18°C)

What arctic bell-heather's hardiness rating actually means

Yes — arctic bell-heather is genuinely cold hardy. Rated RHS H7 and USDA 1-4, 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 1-4 — 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. Arctic Bell-heather is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for arctic bell-heather 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 arctic bell-heather go outside or overwinter — and where?

Plant it out within USDA 1-4 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 arctic bell-heather can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Arctic Bell-heather hardiness — frequently asked questions

Is arctic bell-heather cold hardy?

Yes — arctic bell-heather is genuinely cold hardy. Rated RHS H7 and USDA 1-4, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Arctic Bell-heather is hardy across USDA 1-4; 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 arctic bell-heather can survive?

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

What hardiness zone is arctic bell-heather?

Arctic Bell-heather is rated USDA 1-4 and RHS H7 — Hardy in the severest European continental winters.

Can arctic bell-heather survive winter outside?

Plant it out within USDA 1-4 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 arctic bell-heather 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.