Cold hardiness & minimum temperature

Is Bog Laurel (Kalmia polifolia)cold hardy? Hardiness zone & min temp

Also called Bog laurel, Pale laurel, Swamp laurel, Bog kalmia.

More about bog laurel

About Bog Laurel

Kalmia polifolia · also called Bog laurel, Pale laurel · flowering

A small, creeping evergreen shrub of subarctic and boreal bogs, cold peat swamps, and wet heathlands across North America. Produces bright rose-pink to mauve, saucer-shaped flowers in spring. Exceptionally cold-hardy, tolerating some of the most extreme winters on the continent. All parts are highly toxic via grayanotoxins, including the nectar that can poison honey.

Cold limit: USDA 1-5 · RHS H6 (-45°C to 25°C)

What bog laurel's hardiness rating actually means

Yes — bog laurel is genuinely cold hardy. Rated RHS H6 and USDA 1-5, 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 1-5 — 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. Bog Laurel is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for bog laurel 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 bog laurel go outside or overwinter — and where?

Plant it out within USDA 1-5 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 bog laurel can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Bog Laurel hardiness — frequently asked questions

Is bog laurel cold hardy?

Yes — bog laurel is genuinely cold hardy. Rated RHS H6 and USDA 1-5, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Bog Laurel is hardy across USDA 1-5; 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 bog laurel can survive?

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

What hardiness zone is bog laurel?

Bog Laurel is rated USDA 1-5 and RHS H6 — Hardy throughout the UK and northern Europe.

Can bog laurel survive winter outside?

Plant it out within USDA 1-5 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 bog laurel 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.