Cold hardiness & minimum temperature

Is White Marsh Marigold (Caltha palustris var. alba)cold hardy? Hardiness zone & min temp

Also called White Marsh Marigold, White Kingcup.

More about white marsh marigold

About White Marsh Marigold

Caltha palustris var. alba · also called White Marsh Marigold, White Kingcup · flowering

White Marsh Marigold is a delicate white-flowered variety of the common marsh marigold, producing pure-white, single cup-shaped flowers with golden stamens from February to March — unusually early in the season. Less vigorous than the yellow species, it is best grown as a moisture-loving plant at the pond margin with its growing point above water rather than fully submerged. A charming, subtle alternative for the early-spring bog garden.

Cold limit: USDA 3-7 · RHS H7 (-30 to 22°C)

Watch for — Crown submergence and rot: Planting into standing water — unlike the yellow species — often causes the crown to rot over winter or during wet periods. Always position with the growing point just above the water or soil surface in a permanently moist but non-flooded bog bed.

What white marsh marigold's hardiness rating actually means

Yes — white marsh marigold 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. 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 3-7 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 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 3-7, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. White Marsh Marigold is hardy across USDA 3-7; 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 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 3-7 and RHS H7 — Hardy in the severest European continental winters.

Can white marsh marigold 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 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.