Cold hardiness & minimum temperature

Is Mountain Mint (Pycnanthemum virginianum)cold hardy? Hardiness zone & min temp

Also called Virginia mountain mint, common mountain mint.

More about mountain mint

About Mountain Mint

Pycnanthemum virginianum · also called Virginia mountain mint, common mountain mint · herb

Virginia mountain mint is a bushy native perennial herb of moist meadows and prairies across eastern and central North America, with narrow aromatic leaves and dense clusters of tiny silvery-white flowers in summer. It is one of the most pollinator-rich plants you can grow, and its minty foliage deters deer while attracting bees, wasps, and beneficial insects.

Cold limit: USDA 3-7 · RHS H7 (-37 to 32°C)

Watch for — Root rot in waterlogged soil: Although moisture-loving, it dislikes standing water over winter on heavy clay. Ensure the site drains after rain to prevent crown and root rot.

What mountain mint's hardiness rating actually means

Yes — mountain mint is genuinely cold hardy. Rated RHS H7 and USDA 3-7, 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 3-7 — 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. Mountain Mint is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for mountain mint 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 mountain mint go outside or overwinter — and where?

Plant it out within USDA 3-7 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 mountain mint can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Mountain Mint hardiness — frequently asked questions

Is mountain mint cold hardy?

Yes — mountain mint is genuinely cold hardy. Rated RHS H7 and USDA 3-7, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Mountain Mint is hardy across USDA 3-7; 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 mountain mint can survive?

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

What hardiness zone is mountain mint?

Mountain Mint is rated USDA 3-7 and RHS H7 — Hardy in the severest European continental winters.

Can mountain mint survive winter outside?

Plant it out within USDA 3-7 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 mountain mint 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.