Cold hardiness & minimum temperature

Is Water Violet (Hottonia palustris)cold hardy? Hardiness zone & min temp

Also called Water Violet, Featherfoil.

More about water violet

About Water Violet

Hottonia palustris · also called Water Violet, Featherfoil · flowering

Water Violet is a delicate native submerged aquatic plant bearing finely divided, feathery submerged leaves and elegant spikes of pale lilac-to-white flowers held above the water surface in late spring. Native to Europe, it is one of the most ornamental native oxygenators and is famously included in Dr Bach's original Flower Remedies. Excellent habitat plant for diving beetles and pond snails.

Cold limit: USDA 5-9 · RHS H5 (-10 to 22°C)

What water violet's hardiness rating actually means

Yes — water violet is genuinely cold hardy. Rated RHS H5 and USDA 5-9, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H5 means: Hardy in most of the UK and in cold winters. On the US scale that maps to USDA 5-9 — 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 about −15 to −10 °C. Water Violet is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for water violet as it gets too cold:

It tolerates winter lows to about −15 to −10 °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 water violet go outside or overwinter — and where?

Plant it out within USDA 5-9 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 water violet can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Water Violet hardiness — frequently asked questions

Is water violet cold hardy?

Yes — water violet is genuinely cold hardy. Rated RHS H5 and USDA 5-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Water Violet is hardy across USDA 5-9; 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 water violet can survive?

Minimum survivable temperature is roughly about −15 to −10 °C. Water Violet is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is water violet?

Water Violet is rated USDA 5-9 and RHS H5 — Hardy in most of the UK and in cold winters.

Can water violet survive winter outside?

Plant it out within USDA 5-9 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 water violet below its minimum temperature?

It tolerates winter lows to about −15 to −10 °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.