Cold hardiness & minimum temperature

Is Forked Sundew (Drosera binata)cold hardy? Hardiness zone & min temp

Also called Forked sundew, Fork-leaved sundew, Twin-leaved sundew, Australian sundew.

More about forked sundew

About Forked Sundew

Drosera binata · also called Forked sundew, Fork-leaved sundew · houseplant

Drosera binata is a warm-temperate carnivorous perennial native to Australia and New Zealand, where it grows in sunny, nutrient-poor, seasonally wet bogs and scrub. Its distinctive forked (dichotomous) leaves, covered in red glandular tentacles, branch once, twice, or more times depending on the form — the 'T-form' forks once, while 'multifida' and 'extrema' forms branch repeatedly into dozens of fine arms. It is larger and more robust than most sundews and will catch medium-to-large insects with ease. It goes through a winter dormancy — growth slows or dies back to the roots — that is essential for long-term health. Mildly-toxic by precaution; the genus Drosera is not individually listed by the ASPCA and no significant toxic principles are documented.

Cold limit: USDA 8-10 · RHS H3 (-5 to 35°C (winter dormancy at 4–12°C))

Watch for — Dormancy failure (plant dies without re-sprouting): D. binata must have a winter rest period with cool temperatures and reduced watering; plants kept too warm and wet year-round exhaust their energy reserves and fail to re-emerge. Allow leaves to die back naturally in autumn, reduce the water tray to near-empty, and keep cool (4–12°C) for 8–12 weeks.

What forked sundew's hardiness rating actually means

Forked Sundew is half-hardy (RHS H3). It survives a mild winter outdoors in a sheltered spot, but a hard frost kills it — so in colder zones it is lifted, potted, or grown as a tender plant. Its RHS rating of H3 means: Half-hardy — comes through mild UK winters outside but is killed by a hard freeze. On the US scale that maps to USDA 8-10 — 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 −5 to 1 °C — a light, short frost only. Forked Sundew shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for forked sundew as it gets too cold:

Down to roughly about −5 to 1 °C it copes, especially if dry and sheltered.
A sustained hard frost collapses the top growth; whether it returns depends on whether the roots, crown or tubers froze.
Wet cold is far more lethal than dry cold for this plant — soggy, frozen soil is the usual killer.

Can forked sundew go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 8-10 or a frost-free UK microclimate.
In colder zones, grow it in a pot you can move under cover, or lift its tubers/roots and store them frost-free over winter.
A south-facing wall, free-draining soil and a dry winter position can push it a full zone hardier than the books suggest.

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 forked sundew can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H3 figure above.

Frost protection for borderline forked sundew

Forked Sundew is right on a hardiness edge in many gardens, so if you are pushing it, these measures buy it the margin it needs:

Mulch the crown or root zone deeply with bark, straw or leaf-mould before the first hard frost.
Move container plants against a warm wall or into an unheated but frost-free porch or greenhouse.
Fleece the top growth on the coldest nights, and keep it on the dry side — dry roots survive cold far better than wet ones.
Lift dahlia-type tubers or tender crowns after the first light frost blackens the foliage and store them somewhere cool but frost-free.

Forked Sundew hardiness — frequently asked questions

Is forked sundew cold hardy?

Forked Sundew is half-hardy (RHS H3). It survives a mild winter outdoors in a sheltered spot, but a hard frost kills it — so in colder zones it is lifted, potted, or grown as a tender plant. Borderline outdoors. In its mild end of USDA 8-10 (and sheltered UK gardens) forked sundew can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature forked sundew can survive?

Minimum survivable temperature is roughly about −5 to 1 °C — a light, short frost only. Forked Sundew shrugs off cold nights but a real, sustained freeze will kill it.

What hardiness zone is forked sundew?

Forked Sundew is rated USDA 8-10 and RHS H3 — Half-hardy — comes through mild UK winters outside but is killed by a hard freeze.

Can forked sundew survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 8-10 or a frost-free UK microclimate. In colder zones, grow it in a pot you can move under cover, or lift its tubers/roots and store them frost-free over winter. A south-facing wall, free-draining soil and a dry winter position can push it a full zone hardier than the books suggest.

How do I protect forked sundew from frost?

Mulch the crown or root zone deeply with bark, straw or leaf-mould before the first hard frost. Move container plants against a warm wall or into an unheated but frost-free porch or greenhouse. Fleece the top growth on the coldest nights, and keep it on the dry side — dry roots survive cold far better than wet ones. Lift dahlia-type tubers or tender crowns after the first light frost blackens the foliage and store them somewhere cool but frost-free.