Cold hardiness & minimum temperature

Is Ranunculus aquatilis (Ranunculus aquatilis)cold hardy? Hardiness zone & min temp

Also called White Water Crowfoot, Water Buttercup.

More about ranunculus aquatilis

About Ranunculus aquatilis

Ranunculus aquatilis · also called White Water Crowfoot, Water Buttercup · flowering

White water crowfoot is an aquatic buttercup with two leaf forms: thread-like submerged leaves and lobed floating ones, topped in spring and summer by small white five-petalled flowers held above the water. It oxygenates and shelters pond life in clear, cool, flowing or still water, and provides early colour. Note that, like all buttercups, it is toxic to pets.

Cold limit: USDA 5-9 (outdoor pond) · RHS H6 (5-22°C)

What ranunculus aquatilis's hardiness rating actually means

Yes — ranunculus aquatilis is genuinely cold hardy. Rated RHS H6 and USDA 5-9 (outdoor pond), it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H6 means: Hardy throughout the UK and northern Europe. On the US scale that maps to USDA 5-9 (outdoor pond) — 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 about −20 to −15 °C. Ranunculus aquatilis is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for ranunculus aquatilis as it gets too cold:

It tolerates winter lows to about −20 to −15 °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 ranunculus aquatilis go outside or overwinter — and where?

Plant it out within USDA 5-9 (outdoor pond) 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 ranunculus aquatilis can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Ranunculus aquatilis hardiness — frequently asked questions

Is ranunculus aquatilis cold hardy?

Yes — ranunculus aquatilis is genuinely cold hardy. Rated RHS H6 and USDA 5-9 (outdoor pond), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Ranunculus aquatilis is hardy across USDA 5-9 (outdoor pond); 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 ranunculus aquatilis can survive?

Minimum survivable temperature is roughly about −20 to −15 °C. Ranunculus aquatilis is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is ranunculus aquatilis?

Ranunculus aquatilis is rated USDA 5-9 (outdoor pond) and RHS H6 — Hardy throughout the UK and northern Europe.

Can ranunculus aquatilis survive winter outside?

Plant it out within USDA 5-9 (outdoor pond) 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 ranunculus aquatilis below its minimum temperature?

It tolerates winter lows to about −20 to −15 °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.