Cold hardiness & minimum temperature

Is Ceratopteris thalictroides (Ceratopteris thalictroides)cold hardy? Hardiness zone & min temp

Also called water sprite, Indian fern.

More about ceratopteris thalictroides

About Ceratopteris thalictroides

Ceratopteris thalictroides · also called water sprite, Indian fern · tropical

Ceratopteris thalictroides, water sprite or Indian fern, is a fast-growing aquatic fern for tropical freshwater tanks. Finely dissected, lacy bright-green fronds can be planted in substrate or left floating, where they provide shade and spawning cover. It readily forms plantlets on its leaf margins, multiplies quickly, and acts as a strong nutrient remover that helps suppress algae.

Cold limit: USDA Not applicable (tropical aquarium plant, indoor) · RHS H1b (22-28°C)

What ceratopteris thalictroides's hardiness rating actually means

Ceratopteris thalictroides 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 Not applicable (tropical aquarium plant, indoor) — 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). Ceratopteris thalictroides has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Ceratopteris thalictroides hardiness — frequently asked questions

Is ceratopteris thalictroides cold hardy?

Ceratopteris thalictroides 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. Ceratopteris thalictroides can only live outside year-round in genuinely frost-free climates (roughly USDA Not applicable (tropical aquarium plant, indoor)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature ceratopteris thalictroides can survive?

What hardiness zone is ceratopteris thalictroides?

Ceratopteris thalictroides is rated USDA Not applicable (tropical aquarium plant, indoor) and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can ceratopteris thalictroides 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 ceratopteris thalictroides 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.