Cold hardiness & minimum temperature

Is Slender-Leaved Sundew (Drosera linearis)cold hardy? Hardiness zone & min temp

Also called slender-leaved sundew, linear-leaved sundew.

More about slender-leaved sundew

About Slender-Leaved Sundew

Drosera linearis · also called slender-leaved sundew, linear-leaved sundew · houseplant

Drosera linearis is a delicate North American temperate sundew native to cold, alkaline calcareous bogs — unusual among sundews in tolerating and even preferring limestone-influenced water with slightly higher pH. Narrow upright leaves bear glistening red mucilage glands. Requires cold dormancy and is one of the more challenging sundews for indoor cultivation.

Cold limit: USDA 3-6 · RHS H6 (5–28°C)

Watch for — Failure without cold dormancy: D. linearis is a cold-temperate species requiring 3–5 months of winter dormancy at 2–8°C. Without it, plants exhaust themselves and die within 1–2 years. Move to an unheated greenhouse, cold frame, or refrigerator in winter.

What slender-leaved sundew's hardiness rating actually means

Yes — slender-leaved sundew is genuinely cold hardy. Rated RHS H6 and USDA 3-6, 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 3-6 — 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. Slender-Leaved Sundew is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for slender-leaved sundew 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 slender-leaved sundew go outside or overwinter — and where?

Plant it out within USDA 3-6 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 slender-leaved sundew can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Slender-Leaved Sundew hardiness — frequently asked questions

Is slender-leaved sundew cold hardy?

Yes — slender-leaved sundew is genuinely cold hardy. Rated RHS H6 and USDA 3-6, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Slender-Leaved Sundew is hardy across USDA 3-6; 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 slender-leaved sundew can survive?

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

What hardiness zone is slender-leaved sundew?

Slender-Leaved Sundew is rated USDA 3-6 and RHS H6 — Hardy throughout the UK and northern Europe.

Can slender-leaved sundew survive winter outside?

Plant it out within USDA 3-6 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 slender-leaved sundew 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.