Cold hardiness & minimum temperature

Is River Water Crowfoot (Ranunculus fluitans)cold hardy? Hardiness zone & min temp

Also called river water crowfoot, river buttercup, floating buttercup.

More about river water crowfoot

About River Water Crowfoot

Ranunculus fluitans · also called river water crowfoot, river buttercup · flowering

River Water Crowfoot is a fully submerged aquatic perennial native to fast-flowing rivers across Europe and western Asia. Long, ribbon-like submerged leaves trail dramatically in the current; small white five-petalled flowers emerge above the surface in summer. It oxygenates water, shelters fish fry, and thrives in cool, clear running water.

Cold limit: USDA 4-9 · RHS H7 (5–20°C)

Watch for — Decline in stagnant or warm water: River Water Crowfoot evolved in cool moving water; temperatures above 22°C or stagnant conditions cause stems to rot and the plant to collapse. Increase aeration and shade in summer if water temperatures rise.

What river water crowfoot's hardiness rating actually means

Yes — river water crowfoot is genuinely cold hardy. Rated RHS H7 and USDA 4-9, 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 4-9 — 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. River Water Crowfoot is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for river water crowfoot 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 river water crowfoot go outside or overwinter — and where?

Plant it out within USDA 4-9 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 river water crowfoot can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

River Water Crowfoot hardiness — frequently asked questions

Is river water crowfoot cold hardy?

Yes — river water crowfoot is genuinely cold hardy. Rated RHS H7 and USDA 4-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. River Water Crowfoot is hardy across USDA 4-9; 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 river water crowfoot can survive?

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

What hardiness zone is river water crowfoot?

River Water Crowfoot is rated USDA 4-9 and RHS H7 — Hardy in the severest European continental winters.

Can river water crowfoot survive winter outside?

Plant it out within USDA 4-9 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 river water crowfoot 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.