Cold hardiness & minimum temperature

Is Caladium 'Red Flash' (Caladium bicolor 'Red Flash')cold hardy? Hardiness zone & min temp

Also called Red Flash Caladium.

More about caladium 'red flash'

About Caladium 'Red Flash'

Caladium bicolor 'Red Flash' · also called Red Flash Caladium · houseplant

Caladium 'Red Flash' is a large fancy-leaf caladium with dramatic dark green leaves centred in deep red and peppered with pink spots. A vigorous, sun-tolerant cultivar, it builds a bold mound of big heart-shaped leaves in warm, humid, bright conditions during the growing season, then dies back to a dormant tuber to overwinter warm and dry.

Cold limit: USDA 9-11 (tender tuber; lift or keep frost-free in cooler zones) · RHS H1b (21-29°C)

Watch for — Early leaf collapse: Cold or drought; maintain warmth above 18°C and don't let the large leaves wilt from a dry tuber.

What caladium 'red flash''s hardiness rating actually means

Caladium 'Red Flash' 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 H1b means: Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season. On the US scale that maps to USDA 9-11 (tender tuber; lift or keep frost-free 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 10 °C (sustained cold below this is damaging). Caladium 'Red Flash' has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for caladium 'red flash' as it gets too cold:

Below about about 10 °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 caladium 'red flash' go outside or overwinter — and where?

It can holiday outdoors in summer once nights are reliably above 10 °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 caladium 'red flash' can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1b figure above.

Caladium 'Red Flash' hardiness — frequently asked questions

Is caladium 'red flash' cold hardy?

Caladium 'Red Flash' 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. Caladium 'Red Flash' can only live outside year-round in genuinely frost-free climates (roughly USDA 9-11 (tender tuber; lift or keep frost-free in cooler zones)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature caladium 'red flash' can survive?

What hardiness zone is caladium 'red flash'?

Caladium 'Red Flash' is rated USDA 9-11 (tender tuber; lift or keep frost-free in cooler zones) and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can caladium 'red flash' survive winter outside?

It can holiday outdoors in summer once nights are reliably above 10 °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 caladium 'red flash' below its minimum temperature?

Below about about 10 °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.