Cold hardiness & minimum temperature

Is Dahlia 'Boom Boom White' (Dahlia 'Boom Boom White')cold hardy? Hardiness zone & min temp

Also called Boom Boom White dahlia, white ball dahlia, pom-pom dahlia.

More about dahlia 'boom boom white'

About Dahlia 'Boom Boom White'

Dahlia 'Boom Boom White' · also called Boom Boom White dahlia, white ball dahlia · flowering

Dahlia 'Boom Boom White' is a tuberous dahlia bearing rounded, fully double pure-white ball blooms on upright stems from midsummer to frost. Ideal for cutting and white-themed borders, it grows from a tender tuber lifted or mulched over winter in cold regions. It needs full sun, rich free-draining soil, steady water and routine 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 over winter: Stored tubers rot if kept damp or are caught by frost. Lift after first frost, dry off, and store cool and barely moist in cold zones.

What dahlia 'boom boom white''s hardiness rating actually means

Dahlia 'Boom Boom White' 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 'Boom Boom White' shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for dahlia 'boom boom white' 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 'boom boom white' 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 'boom boom white' 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 'boom boom white'

Dahlia 'Boom Boom White' 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 'Boom Boom White' hardiness — frequently asked questions

Is dahlia 'boom boom white' cold hardy?

Dahlia 'Boom Boom White' 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 'boom boom white' 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 'boom boom white' can survive?

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

What hardiness zone is dahlia 'boom boom white'?

Dahlia 'Boom Boom White' 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 'boom boom white' 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 'boom boom white' 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.