Cold hardiness & minimum temperature

Is Double Click Snow Puff cosmos (Cosmos bipinnatus 'Double Click Snow Puff')cold hardy? Hardiness zone & min temp

Also called Double Click Snow Puff cosmos, Double Click Snow Puff.

More about double click snow puff cosmos

About Double Click Snow Puff cosmos

Cosmos bipinnatus 'Double Click Snow Puff' · also called Double Click Snow Puff cosmos, Double Click Snow Puff · flowering

A fully double-flowered white cosmos producing fluffy, pompon-like blooms on airy, finely cut foliage. Thrives in full sun with lean, well-drained soil — excess fertility reduces flowering. Direct-sow after last frost or start indoors 4–6 weeks early. Excellent as a cut flower and highly attractive to pollinators.

Cold limit: USDA 2–11 (grown as annual) · RHS H2 (10–30°C)

What double click snow puff cosmos's hardiness rating actually means

Double Click Snow Puff cosmos 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 2–11 (grown as annual) — 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. Double Click Snow Puff cosmos shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for double click snow puff cosmos 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 double click snow puff cosmos go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 2–11 (grown as annual) 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 double click snow puff cosmos 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 double click snow puff cosmos

Double Click Snow Puff cosmos 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.

Double Click Snow Puff cosmos hardiness — frequently asked questions

Is double click snow puff cosmos cold hardy?

Double Click Snow Puff cosmos 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 2–11 (grown as annual) (and sheltered UK gardens) double click snow puff cosmos can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature double click snow puff cosmos can survive?

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

What hardiness zone is double click snow puff cosmos?

Double Click Snow Puff cosmos is rated USDA 2–11 (grown as annual) and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can double click snow puff cosmos survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 2–11 (grown as annual) 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 double click snow puff cosmos 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.