Cold hardiness & minimum temperature

Is Philodendron Imperial Red (Philodendron erubescens 'Imperial Red')cold hardy? Hardiness zone & min temp

Also called Imperial Red Philodendron, Red-leaf Philodendron 'Imperial Red', Blushing Philodendron 'Imperial Red'.

More about philodendron imperial red

About Philodendron Imperial Red

Philodendron erubescens 'Imperial Red' · also called Imperial Red Philodendron, Red-leaf Philodendron 'Imperial Red' · houseplant

Philodendron 'Imperial Red' is a compact, self-heading aroid prized for glossy leaves that emerge deep burgundy-red before maturing to dark green. It thrives in bright indirect light, evenly moist soil, and warmth (18-29C). Easy to grow but toxic to cats and dogs per ASPCA, so keep it out of reach.

Cold limit: USDA 9b-11 (outdoors); grown as a houseplant elsewhere (18-29C)

What philodendron imperial red's hardiness rating actually means

Philodendron Imperial Red 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 9b-11 (outdoors); grown as a houseplant elsewhere — 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). Philodendron Imperial Red has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for philodendron imperial red 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 philodendron imperial red 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 philodendron imperial red can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1b figure above.

Philodendron Imperial Red hardiness — frequently asked questions

Is philodendron imperial red cold hardy?

Philodendron Imperial Red 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. Philodendron Imperial Red can only live outside year-round in genuinely frost-free climates (roughly USDA 9b-11 (outdoors); grown as a houseplant elsewhere); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature philodendron imperial red can survive?

What hardiness zone is philodendron imperial red?

Philodendron Imperial Red is rated USDA 9b-11 (outdoors); grown as a houseplant elsewhere and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can philodendron imperial red 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 philodendron imperial red 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.