Cold hardiness & minimum temperature

Is Hibiscus rosa-sinensis 'Cooper' (Hibiscus rosa-sinensis 'Cooper')cold hardy? Hardiness zone & min temp

Also called Cooper hibiscus, variegated hibiscus.

More about hibiscus rosa-sinensis 'cooper'

About Hibiscus rosa-sinensis 'Cooper'

Hibiscus rosa-sinensis 'Cooper' · also called Cooper hibiscus, variegated hibiscus · tropical

Hibiscus rosa-sinensis 'Cooper' is a tropical evergreen shrub grown as much for its striking cream, pink and green variegated foliage as for its scarlet trumpet flowers. Tender and sun-loving, it makes a vivid container or conservatory plant that summers outdoors and overwinters frost-free indoors. The colourful leaves need strong light to keep their bright pink-and-white markings.

Cold limit: USDA 10-12 (indoor/conservatory in most of the US and UK; frost-tender) · RHS H1c (16-30°C)

Watch for — Bud drop: Caused by sudden changes in light, temperature or watering, or by low humidity. Keep conditions steady and avoid moving a budded plant.

What hibiscus rosa-sinensis 'cooper''s hardiness rating actually means

Hibiscus rosa-sinensis 'Cooper' is not cold hardy. It is a tropical houseplant that dies if it is left out through frost — there is no zone where it overwinters outdoors in a UK or cold-US climate. Its RHS rating of H1c means: Warm-temperate — can summer outdoors but must come in well before the first frost. On the US scale that maps to USDA 10-12 (indoor/conservatory in most of the US and UK; frost-tender) — 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 °C (and never frost). Hibiscus rosa-sinensis 'Cooper' has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for hibiscus rosa-sinensis 'cooper' as it gets too cold:

Below about about 5 °C, growth stalls and the leaves start to show cold stress — dark, water-soaked, or yellowing patches.
A single light frost blackens the foliage; a hard freeze kills the whole plant, roots included, and it does not recover.
Even a cold, draughty windowsill or an unheated porch in winter can be enough to damage it permanently.

Can hibiscus rosa-sinensis 'cooper' go outside or overwinter — and where?

It can holiday outdoors in summer once nights are reliably above 5 °C, in shade or dappled light, hardened off gradually.
Bring it back indoors well before the first autumn frost — do not wait for a frost warning, move it when nights drop toward 10-12 °C.
It will never overwinter outside in a temperate climate; the indoors is its winter home, full stop.

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 hibiscus rosa-sinensis 'cooper' can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

Hibiscus rosa-sinensis 'Cooper' hardiness — frequently asked questions

Is hibiscus rosa-sinensis 'cooper' cold hardy?

Hibiscus rosa-sinensis 'Cooper' is not cold hardy. It is a tropical houseplant that dies if it is left out through frost — there is no zone where it overwinters outdoors in a UK or cold-US climate. Indoor-only in almost every home. Hibiscus rosa-sinensis 'Cooper' can only live outside year-round in genuinely frost-free climates (roughly USDA 10-12 (indoor/conservatory in most of the US and UK; frost-tender)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature hibiscus rosa-sinensis 'cooper' can survive?

Minimum survivable temperature is roughly about 5 °C (and never frost). Hibiscus rosa-sinensis 'Cooper' has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

What hardiness zone is hibiscus rosa-sinensis 'cooper'?

Hibiscus rosa-sinensis 'Cooper' is rated USDA 10-12 (indoor/conservatory in most of the US and UK; frost-tender) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can hibiscus rosa-sinensis 'cooper' survive winter outside?

It can holiday outdoors in summer once nights are reliably above 5 °C, in shade or dappled light, hardened off gradually. Bring it back indoors well before the first autumn frost — do not wait for a frost warning, move it when nights drop toward 10-12 °C. It will never overwinter outside in a temperate climate; the indoors is its winter home, full stop.

What happens to hibiscus rosa-sinensis 'cooper' below its minimum temperature?

Below about about 5 °C, growth stalls and the leaves start to show cold stress — dark, water-soaked, or yellowing patches. A single light frost blackens the foliage; a hard freeze kills the whole plant, roots included, and it does not recover. Even a cold, draughty windowsill or an unheated porch in winter can be enough to damage it permanently.