Cold hardiness & minimum temperature

Is Dickie's Bladder Fern (Cystopteris dickieana)cold hardy? Hardiness zone & min temp

Also called Dickie's Bladder Fern, Dickie's Bladder-fern.

More about dickie's bladder fern

About Dickie's Bladder Fern

Cystopteris dickieana · also called Dickie's Bladder Fern, Dickie's Bladder-fern · houseplant

Cystopteris dickieana is a rare, delicate semi-evergreen fern with a circumpolar Northern Hemisphere distribution, including Scotland, Scandinavia, North America, Russia, and the Atlas Mountains of North Africa, where it colonises moist, shaded rock crevices both on the coast and in upland montane sites. In the UK it is a protected species confined to a small number of Scottish montane and coastal cave localities, making it of significant conservation interest. Despite its rarity, it is relatively straightforward to cultivate given cool, moist, shaded conditions and freely-draining rocky or peaty soil. Not listed as toxic to cats or dogs by the ASPCA.

Cold limit: USDA 3-7 · RHS H7 (-30 to 18°C)

What dickie's bladder fern's hardiness rating actually means

Yes — dickie's bladder fern is genuinely cold hardy. Rated RHS H7 and USDA 3-7, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H7 means: Hardy in the severest European continental winters. On the US scale that maps to USDA 3-7 — 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 below about −20 °C. Dickie's Bladder Fern is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for dickie's bladder fern as it gets too cold:

It tolerates winter lows to about −20 °C once established.
Below its rated zone, the visible damage is browned or blackened top growth and, in the worst case, a killed crown or root.
First-year, newly planted, or container-grown specimens are noticeably less hardy than established garden plants — the roots are exposed.

Can dickie's bladder fern go outside or overwinter — and where?

Plant it out within USDA 3-7 and it overwinters with little or no help.
It does not want to come indoors — a warm winter room actually weakens a hardy plant by denying it dormancy.
The real risks in its range are waterlogging, wind-rock on young plants, and a late hard frost on new growth — not ordinary winter cold.

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 dickie's bladder fern can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Dickie's Bladder Fern hardiness — frequently asked questions

Is dickie's bladder fern cold hardy?

Yes — dickie's bladder fern is genuinely cold hardy. Rated RHS H7 and USDA 3-7, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Dickie's Bladder Fern is hardy across USDA 3-7; it belongs in the ground or a frost-proof container, not on a windowsill, and many types actively need a cold winter to perform.

What is the minimum temperature dickie's bladder fern can survive?

Minimum survivable temperature is roughly below about −20 °C. Dickie's Bladder Fern is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is dickie's bladder fern?

Dickie's Bladder Fern is rated USDA 3-7 and RHS H7 — Hardy in the severest European continental winters.

Can dickie's bladder fern survive winter outside?

Plant it out within USDA 3-7 and it overwinters with little or no help. It does not want to come indoors — a warm winter room actually weakens a hardy plant by denying it dormancy. The real risks in its range are waterlogging, wind-rock on young plants, and a late hard frost on new growth — not ordinary winter cold.

What happens to dickie's bladder fern below its minimum temperature?

It tolerates winter lows to about −20 °C once established. Below its rated zone, the visible damage is browned or blackened top growth and, in the worst case, a killed crown or root. First-year, newly planted, or container-grown specimens are noticeably less hardy than established garden plants — the roots are exposed.