Cold hardiness & minimum temperature

Is Hydrocharis morsus-ranae (Hydrocharis morsus-ranae)cold hardy? Hardiness zone & min temp

Also called Frogbit, Common Frogbit, European Frogbit.

More about hydrocharis morsus-ranae

About Hydrocharis morsus-ranae

Hydrocharis morsus-ranae · also called Frogbit, Common Frogbit · flowering

Frogbit is a free-floating aquatic that looks like a miniature water lily, with small kidney-shaped leaves and three-petalled white flowers in summer. It drifts on the surface of still ponds, spreading fast by runners and overwintering as sunken buds (turions). Pretty and easy in a contained pond, but invasive in parts of North America, so check local restrictions.

Cold limit: USDA 5-10 (outdoor pond) · RHS H5 (5-25°C)

Watch for — Disappearing in autumn: Leaves rot and the plant overwinters as sunken turions; this is normal dormancy, not death, and it reappears in spring.

What hydrocharis morsus-ranae's hardiness rating actually means

Yes — hydrocharis morsus-ranae is genuinely cold hardy. Rated RHS H5 and USDA 5-10 (outdoor pond), 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 5-10 (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 −15 to −10 °C. Hydrocharis morsus-ranae is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for hydrocharis morsus-ranae 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 hydrocharis morsus-ranae go outside or overwinter — and where?

Plant it out within USDA 5-10 (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 hydrocharis morsus-ranae can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Hydrocharis morsus-ranae hardiness — frequently asked questions

Is hydrocharis morsus-ranae cold hardy?

Yes — hydrocharis morsus-ranae is genuinely cold hardy. Rated RHS H5 and USDA 5-10 (outdoor pond), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Hydrocharis morsus-ranae is hardy across USDA 5-10 (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 hydrocharis morsus-ranae can survive?

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

What hardiness zone is hydrocharis morsus-ranae?

Hydrocharis morsus-ranae is rated USDA 5-10 (outdoor pond) and RHS H5 — Hardy in most of the UK and in cold winters.

Can hydrocharis morsus-ranae survive winter outside?

Plant it out within USDA 5-10 (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 hydrocharis morsus-ranae 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.