Cold hardiness & minimum temperature

Is Confederate Rose (Hibiscus mutabilis)cold hardy? Hardiness zone & min temp

Also called Confederate rose, cotton rose, changeable rose, rose of autumn, Confederate rose mallow.

More about confederate rose

About Confederate Rose

Hibiscus mutabilis · also called Confederate rose, cotton rose · flowering

Confederate rose is a spectacular semi-tropical shrub or small tree renowned for its flowers that open white or pale pink in the morning and deepen to rose-red or deep crimson by evening, creating a multicoloured display on the same plant. Hardy in USDA Zones 7–11, it dies to the ground in frost but regenerates vigorously from the roots, producing enormous blooms from late summer through autumn.

Cold limit: USDA 7-11 · RHS H3 (-12°C to 38°C (10°F to 100°F))

Watch for — Freeze dieback in Zones 7–8: The top growth is killed by hard frost in Zones 7–8 but roots survive; mulch the root zone heavily in autumn, cut stems back after frost, and wait until mid-spring before new shoots emerge from the base — do not give up on apparently dead plants too early.

What confederate rose's hardiness rating actually means

Confederate Rose 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 7-11 — 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. Confederate Rose shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for confederate rose 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 confederate rose go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 7-11 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 confederate rose 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 confederate rose

Confederate Rose 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.

Confederate Rose hardiness — frequently asked questions

Is confederate rose cold hardy?

Confederate Rose 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 7-11 (and sheltered UK gardens) confederate rose can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature confederate rose can survive?

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

What hardiness zone is confederate rose?

Confederate Rose is rated USDA 7-11 and RHS H3 — Half-hardy — comes through mild UK winters outside but is killed by a hard freeze.

Can confederate rose survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 7-11 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 confederate rose 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.