Cold hardiness & minimum temperature

Is Scarlet Sundew (Drosera scorpioides)cold hardy? Hardiness zone & min temp

Also called Scarlet sundew, Shaggy sundew, Scorpion sundew.

More about scarlet sundew

About Scarlet Sundew

Drosera scorpioides · also called Scarlet sundew, Shaggy sundew · houseplant

Drosera scorpioides is the largest of the pygmy sundews, native to the Jarrah Forest region and southern coastal heathlands of south-west Western Australia, where it grows in sandy, nutrient-poor soils in a Mediterranean climate. It forms vivid scarlet rosettes that can grow atop stems up to 15–18 cm tall over several years, and produces pale pink flowers in winter through early spring. The critical care rule is its winter-active, summer-dormant rhythm: plants tolerate mild frosts but must not be subjected to summer heat and wet simultaneously. Drosera is not listed in the ASPCA database; classify as mildly-toxic for pets.

Cold limit: USDA 9-11 (outdoor in frost-light, dry-summer climates) · RHS H2 (5–28 °C)

Watch for — Crown rot in warm humid conditions: High temperature combined with high humidity and wet soil is fatal; reduce watering and improve airflow as temperatures exceed 25 °C, allowing the plant to transition to its natural summer dormancy.

What scarlet sundew's hardiness rating actually means

Scarlet Sundew is half-hardy (RHS H2). 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 H2 means: Tender — survives a frost-free greenhouse or a very mild, sheltered spot. On the US scale that maps to USDA 9-11 (outdoor in frost-light, dry-summer climates) — 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 1 to 5 °C — tolerates cold but no real frost. Scarlet Sundew shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for scarlet sundew as it gets too cold:

Down to roughly about 1 to 5 °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 scarlet sundew go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 9-11 (outdoor in frost-light, dry-summer climates) 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 scarlet sundew can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H2 figure above.

Frost protection for borderline scarlet sundew

Scarlet 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.

Scarlet Sundew hardiness — frequently asked questions

Is scarlet sundew cold hardy?

Scarlet Sundew is half-hardy (RHS H2). 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 9-11 (outdoor in frost-light, dry-summer climates) (and sheltered UK gardens) scarlet 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 scarlet sundew can survive?

Minimum survivable temperature is roughly about 1 to 5 °C — tolerates cold but no real frost. Scarlet Sundew shrugs off cold nights but a real, sustained freeze will kill it.

What hardiness zone is scarlet sundew?

Scarlet Sundew is rated USDA 9-11 (outdoor in frost-light, dry-summer climates) and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can scarlet sundew survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 9-11 (outdoor in frost-light, dry-summer climates) 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 scarlet 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.