Cold hardiness & minimum temperature

Is White Marsh Marigold (Caltha leptosepala)cold hardy? Hardiness zone & min temp

Also called White Marsh Marigold, Western Marsh Marigold, Howell's Marsh Marigold, Elkslip.

More about white marsh marigold

About White Marsh Marigold

Caltha leptosepala · also called White Marsh Marigold, Western Marsh Marigold · flowering

Caltha leptosepala is a North American alpine and subalpine marsh marigold native to mountain wetlands from Alaska to New Mexico, producing pure-white, single flowers with prominent golden stamens in late spring to early summer as snowmelt floods mountain streams and bogs. More cold-tolerant and compact than European marsh marigold species, it suits cool-climate water gardens and is fully hardy to extreme cold.

Cold limit: USDA 3-8 · RHS H7 (-40 to 20°C)

Watch for — Summer dormancy and die-back: In warm lowland gardens Caltha leptosepala may go dormant by midsummer once temperatures consistently exceed 25°C (77°F), leaving bare patches. This is normal behaviour. Mark the planting position to avoid accidental disturbance; top-dress with leaf mould and the plant will re-emerge the following spring.

What white marsh marigold's hardiness rating actually means

Yes — white marsh marigold is genuinely cold hardy. Rated RHS H7 and USDA 3-8, 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 3-8 — 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. White Marsh Marigold is built for winter — once established it takes hard frost and snow in its stride.

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

Plant it out within USDA 3-8 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 white marsh marigold can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

White Marsh Marigold hardiness — frequently asked questions

Is white marsh marigold cold hardy?

Yes — white marsh marigold is genuinely cold hardy. Rated RHS H7 and USDA 3-8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. White Marsh Marigold is hardy across USDA 3-8; 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 white marsh marigold can survive?

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

What hardiness zone is white marsh marigold?

White Marsh Marigold is rated USDA 3-8 and RHS H7 — Hardy in the severest European continental winters.

Can white marsh marigold survive winter outside?

Plant it out within USDA 3-8 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 white marsh marigold 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.