Cold hardiness & minimum temperature

Is Drosera Filiformis (Drosera filiformis)cold hardy? Hardiness zone & min temp

Also called thread-leaved sundew, filiform sundew.

More about drosera filiformis

About Drosera Filiformis

Drosera filiformis · also called thread-leaved sundew, filiform sundew · houseplant

Drosera filiformis, the thread-leaved sundew, is a temperate North American carnivore with erect, thread-like leaves up to 25 cm tall, entirely coated in glistening sticky tentacles that trap and curl around insects. A bog plant of the US eastern seaboard, it needs full sun, permanently wet soft soil, and a cold winter dormancy in which it dies back to a hibernaculum bud.

Cold limit: USDA 6-9 (the northern form is hardier; needs cold dormancy) · RHS H4 (21-32°C summer; 0-10°C winter dormancy)

Watch for — Leaves dying back in autumn: Normal dormancy — it forms a hibernaculum and rests over winter. Keep it cool and just damp; new leaves emerge in spring.

What drosera filiformis's hardiness rating actually means

Yes — drosera filiformis is genuinely cold hardy. Rated RHS H4 and USDA 6-9 (the northern form is hardier; needs cold dormancy), it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H4 means: Hardy in an average winter across much of the temperate world. On the US scale that maps to USDA 6-9 (the northern form is hardier; needs cold dormancy) — 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 −10 to −5 °C. Drosera Filiformis is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for drosera filiformis as it gets too cold:

It tolerates winter lows to about −10 to −5 °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 drosera filiformis go outside or overwinter — and where?

Plant it out within USDA 6-9 (the northern form is hardier; needs cold dormancy) 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 drosera filiformis can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H4 figure above.

Drosera Filiformis hardiness — frequently asked questions

Is drosera filiformis cold hardy?

Yes — drosera filiformis is genuinely cold hardy. Rated RHS H4 and USDA 6-9 (the northern form is hardier; needs cold dormancy), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Drosera Filiformis is hardy across USDA 6-9 (the northern form is hardier; needs cold dormancy); 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 drosera filiformis can survive?

Minimum survivable temperature is roughly about −10 to −5 °C. Drosera Filiformis is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is drosera filiformis?

Drosera Filiformis is rated USDA 6-9 (the northern form is hardier; needs cold dormancy) and RHS H4 — Hardy in an average winter across much of the temperate world.

Can drosera filiformis survive winter outside?

Plant it out within USDA 6-9 (the northern form is hardier; needs cold dormancy) 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 drosera filiformis below its minimum temperature?

It tolerates winter lows to about −10 to −5 °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.