Cold hardiness & minimum temperature

Is Bog rosemary (Andromeda polifolia)cold hardy? Hardiness zone & min temp

Also called Bog rosemary, Marsh andromeda.

More about bog rosemary

About Bog rosemary

Andromeda polifolia · also called Bog rosemary, Marsh andromeda · flowering

Bog rosemary is a compact evergreen subshrub native to Northern Hemisphere bogs and tundra. Its narrow, grey-green leaves resemble rosemary and it bears delicate pink urn-shaped flowers in spring. Suited to acidic, permanently moist conditions in rock gardens or bog plantings, it is fully hardy and tolerates challenging cold climates.

Cold limit: USDA 2-6 · RHS H7 (-30°C to 25°C)

What bog rosemary's hardiness rating actually means

Yes — bog rosemary 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. Bog rosemary is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for bog rosemary 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 bog rosemary 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 bog rosemary can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Bog rosemary hardiness — frequently asked questions

Is bog rosemary cold hardy?

Yes — bog rosemary 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. Bog rosemary 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 bog rosemary can survive?

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

What hardiness zone is bog rosemary?

Bog rosemary is rated USDA 2-6 and RHS H7 — Hardy in the severest European continental winters.

Can bog rosemary 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 bog rosemary 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.