Cold hardiness & minimum temperature

Is Roundleaf Sundew (Drosera rotundifolia)cold hardy? Hardiness zone & min temp

Also called Common sundew.

More about roundleaf sundew

About Roundleaf Sundew

Drosera rotundifolia · also called Common sundew · flowering

Drosera rotundifolia is the temperate roundleaf sundew native to acidic bogs across the Northern Hemisphere. Its flat rosette of round, long-stalked leaves bristles with red, dew-tipped tentacles that trap small insects. Fully cold-hardy, it forms a winter resting bud (hibernaculum) and demands a genuine cold dormancy, pure water, and permanently wet, acidic peat.

Cold limit: USDA 3-9 · RHS H7 (-15-28°C)

Watch for — Rot during winter: Standing water on the dormant hibernaculum causes rot. Keep merely damp, not flooded, and ensure airflow over winter.

What roundleaf sundew's hardiness rating actually means

Yes — roundleaf sundew is genuinely cold hardy. Rated RHS H7 and USDA 3-9, 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 3-9 — 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. Roundleaf Sundew is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for roundleaf sundew 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 roundleaf sundew go outside or overwinter — and where?

Plant it out within USDA 3-9 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 roundleaf sundew can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Roundleaf Sundew hardiness — frequently asked questions

Is roundleaf sundew cold hardy?

Yes — roundleaf sundew is genuinely cold hardy. Rated RHS H7 and USDA 3-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Roundleaf Sundew is hardy across USDA 3-9; 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 roundleaf sundew can survive?

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

What hardiness zone is roundleaf sundew?

Roundleaf Sundew is rated USDA 3-9 and RHS H7 — Hardy in the severest European continental winters.

Can roundleaf sundew survive winter outside?

Plant it out within USDA 3-9 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 roundleaf sundew 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.