Cold hardiness & minimum temperature

Is Crocodile fern (Microsorum musifolium)cold hardy? Hardiness zone & min temp

Also called alligator fern, crocodile leaf fern.

About Crocodile fern

Microsorum musifolium · also called alligator fern, crocodile leaf fern · houseplant

Crocodile fern is a tropical Asian fern with broad strap leaves marked with a striking dark crocodile-skin pattern. Pet-safe and prefers high humidity. Easier than maidenhair fern but still needs consistent moisture.

Microsorum musifolium, an epiphytic fern native from southern Myanmar through Indonesia, Borneo and New Guinea, growing on rainforest tree trunks and branches, not in ground soil.

Erect, arching habit roughly 30-90cm tall and wide, with broad strap-like fronds whose puckered network of darker veins gives the crocodile-skin look; best propagated by spring division.

Cold limit: USDA 10-12 (indoor in most US homes) · RHS H1b (18-27°C)

Sources: plants.ces.ncsu.edu, missouribotanicalgarden.org

What crocodile fern's hardiness rating actually means

Crocodile 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 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 10-12 (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 10 °C (sustained cold below this is damaging). Crocodile fern has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Crocodile fern hardiness — frequently asked questions

Is crocodile fern cold hardy?

Crocodile 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. Crocodile fern can only live outside year-round in genuinely frost-free climates (roughly USDA 10-12 (indoor in most US homes)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature crocodile fern can survive?

What hardiness zone is crocodile fern?

Crocodile fern is rated USDA 10-12 (indoor in most US homes) and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can crocodile fern 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 crocodile fern 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.