Cold hardiness & minimum temperature

Is Marsh Woundwort (Stachys palustris)cold hardy? Hardiness zone & min temp

Also called Marsh Woundwort, Marsh Hedgenettle, Clown's Woundwort.

More about marsh woundwort

About Marsh Woundwort

Stachys palustris · also called Marsh Woundwort, Marsh Hedgenettle · herb

Stachys palustris is a native British perennial herb in the mint family (Lamiaceae), found along riverbanks, ditches, marshes, and wet meadows across the UK, Europe, and Asia. It produces upright square stems bearing whorls of hooded, lipped, pinkish-purple flowers in mid-summer that attract bumblebees. The most critical care point is to provide consistently moist to wet soil and to contain the spreading rhizomes, which can colonise far beyond the original planting. It is not listed by the ASPCA and formal pet-toxicity status is unconfirmed; treat as mildly toxic as a precaution.

Cold limit: USDA 4-8 · RHS H7 (-25 to 28°C)

What marsh woundwort's hardiness rating actually means

Yes — marsh woundwort is genuinely cold hardy. Rated RHS H7 and USDA 4-8, 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 4-8 — 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. Marsh Woundwort is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for marsh woundwort 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 marsh woundwort go outside or overwinter — and where?

Plant it out within USDA 4-8 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 marsh woundwort can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Marsh Woundwort hardiness — frequently asked questions

Is marsh woundwort cold hardy?

Yes — marsh woundwort is genuinely cold hardy. Rated RHS H7 and USDA 4-8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Marsh Woundwort is hardy across USDA 4-8; 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 marsh woundwort can survive?

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

What hardiness zone is marsh woundwort?

Marsh Woundwort is rated USDA 4-8 and RHS H7 — Hardy in the severest European continental winters.

Can marsh woundwort survive winter outside?

Plant it out within USDA 4-8 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 marsh woundwort 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.