Cold hardiness & minimum temperature

Is Pelargonium x domesticum 'Carisbrooke' (Pelargonium x domesticum 'Carisbrooke')cold hardy? Hardiness zone & min temp

Also called Carisbrooke regal pelargonium, Martha Washington geranium Carisbrooke.

More about pelargonium x domesticum 'carisbrooke'

About Pelargonium x domesticum 'Carisbrooke'

Pelargonium x domesticum 'Carisbrooke' · also called Carisbrooke regal pelargonium, Martha Washington geranium Carisbrooke · flowering

'Carisbrooke' is a regal (Martha Washington) pelargonium with large, ruffled rose-pink flowers feathered and blotched with deeper maroon markings. Regals bloom in a concentrated spring-to-early-summer flush on upright, bushy plants with toothed, slightly sticky leaves. They prefer cooler nights than zonals and are usually grown under glass or as patio specimens, treated as tender perennials.

Cold limit: USDA 9-11 (grown frost-free under glass or as a houseplant in cooler zones) · RHS H2 (10-21°C)

Watch for — Short flowering season: Regals bloom in one main spring flush; a cool rest at 7-10°C over winter and bright spring light maximise the next display.

What pelargonium x domesticum 'carisbrooke''s hardiness rating actually means

Pelargonium x domesticum 'Carisbrooke' 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 (grown frost-free under glass or as a houseplant in cooler zones) — 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. Pelargonium x domesticum 'Carisbrooke' shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for pelargonium x domesticum 'carisbrooke' 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 pelargonium x domesticum 'carisbrooke' go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 9-11 (grown frost-free under glass or as a houseplant in cooler zones) 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 pelargonium x domesticum 'carisbrooke' 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 pelargonium x domesticum 'carisbrooke'

Pelargonium x domesticum 'Carisbrooke' 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.

Pelargonium x domesticum 'Carisbrooke' hardiness — frequently asked questions

Is pelargonium x domesticum 'carisbrooke' cold hardy?

Pelargonium x domesticum 'Carisbrooke' 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 (grown frost-free under glass or as a houseplant in cooler zones) (and sheltered UK gardens) pelargonium x domesticum 'carisbrooke' can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature pelargonium x domesticum 'carisbrooke' can survive?

What hardiness zone is pelargonium x domesticum 'carisbrooke'?

Pelargonium x domesticum 'Carisbrooke' is rated USDA 9-11 (grown frost-free under glass or as a houseplant in cooler zones) and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can pelargonium x domesticum 'carisbrooke' survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 9-11 (grown frost-free under glass or as a houseplant in cooler zones) 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 pelargonium x domesticum 'carisbrooke' 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.