Cold hardiness & minimum temperature

Is Heart Fern (Hemionitis arifolia)cold hardy? Hardiness zone & min temp

Also called Heart fern, Heart-leaf fern, Tongue fern.

More about heart fern

About Heart Fern

Hemionitis arifolia · also called Heart fern, Heart-leaf fern · houseplant

The heart fern (Hemionitis arifolia) is a compact tropical true fern grown for its glossy, heart-shaped fronds. It wants bright indirect light, evenly moist soil, and high humidity above 60 percent, making it ideal for terrariums. It is not individually listed by the ASPCA, so confirm pet safety with your vet.

Cold limit: USDA 10-11 (grown as a houseplant in cooler climates) (15-29°C)

What heart fern's hardiness rating actually means

Heart Fern 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 10-11 (grown as a houseplant in cooler climates) — 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). Heart Fern has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for heart fern 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 heart fern 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 heart fern can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

Heart Fern hardiness — frequently asked questions

Is heart fern cold hardy?

Heart Fern 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. Heart Fern can only live outside year-round in genuinely frost-free climates (roughly USDA 10-11 (grown as a houseplant in cooler climates)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature heart fern can survive?

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

What hardiness zone is heart fern?

Heart Fern is rated USDA 10-11 (grown as a houseplant in cooler climates) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can heart fern 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 heart fern 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.