Cold hardiness & minimum temperature

Is Button fern (Pellaea rotundifolia)cold hardy? Hardiness zone & min temp

Also called New Zealand button fern, tarawera.

About Button fern

Pellaea rotundifolia · also called New Zealand button fern, tarawera · houseplant

Button fern is a small evergreen from New Zealand and Australia with round dark green leaflets on wiry stems. More drought-tolerant than most ferns and pet-safe. Good for terrariums and small pots.

Pellaea rotundifolia, native to New Zealand and Australia where, unusually for a fern, it grows in rocky, comparatively dry habitats rather than damp forest floor.

Compact evergreen reaching only about 25cm, with pinnate fronds of round, deep-green leathery leaflets on dark brown, pink-scaled rachises that give it its name.

Cold limit: USDA 9-11 (indoor in most US homes) · RHS H1c (15-24°C)

Sources: rhs.org.uk, gardenia.net

What button fern's hardiness rating actually means

Button 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 9-11 (indoor in most US homes) — 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). Button fern has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Button fern hardiness — frequently asked questions

Is button fern cold hardy?

Button 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. Button fern can only live outside year-round in genuinely frost-free climates (roughly USDA 9-11 (indoor in most US homes)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature button fern can survive?

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

What hardiness zone is button fern?

Button fern is rated USDA 9-11 (indoor in most US homes) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can button 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 button 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.