Cold hardiness & minimum temperature

Is Dahlia 'Ace Summer Sunset' (Dahlia 'Ace Summer Sunset')cold hardy? Hardiness zone & min temp

Also called Ace Summer Sunset dahlia, orange cactus dahlia.

More about dahlia 'ace summer sunset'

About Dahlia 'Ace Summer Sunset'

Dahlia 'Ace Summer Sunset' · also called Ace Summer Sunset dahlia, orange cactus dahlia · flowering

Dahlia 'Ace Summer Sunset' is a tuberous dahlia with vivid orange, spiky-petalled cactus-form blooms on tall, strong stems from midsummer to frost. A striking cut flower and border plant, it grows from a tender tuber lifted or mulched in cold areas. It wants full sun, rich free-draining soil, steady moisture, staking and regular deadheading.

Cold limit: USDA 8-10 in ground; lift and store tubers in zone 7 and colder · RHS H3 (16-27°C)

Watch for — Tuber rot in storage: Overwintered tubers rot if stored damp or frozen. Lift after the first frost, dry, and store cool, dark and barely moist in cold zones.

What dahlia 'ace summer sunset''s hardiness rating actually means

Dahlia 'Ace Summer Sunset' 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 in ground; lift and store tubers in zone 7 and colder — 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. Dahlia 'Ace Summer Sunset' shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for dahlia 'ace summer sunset' 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 dahlia 'ace summer sunset' go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 8-10 in ground; lift and store tubers in zone 7 and colder 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 dahlia 'ace summer sunset' 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 dahlia 'ace summer sunset'

Dahlia 'Ace Summer Sunset' 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.

Dahlia 'Ace Summer Sunset' hardiness — frequently asked questions

Is dahlia 'ace summer sunset' cold hardy?

Dahlia 'Ace Summer Sunset' 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 in ground; lift and store tubers in zone 7 and colder (and sheltered UK gardens) dahlia 'ace summer sunset' can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature dahlia 'ace summer sunset' can survive?

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

What hardiness zone is dahlia 'ace summer sunset'?

Dahlia 'Ace Summer Sunset' is rated USDA 8-10 in ground; lift and store tubers in zone 7 and colder and RHS H3 — Half-hardy — comes through mild UK winters outside but is killed by a hard freeze.

Can dahlia 'ace summer sunset' survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 8-10 in ground; lift and store tubers in zone 7 and colder 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 dahlia 'ace summer sunset' 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.