Cold hardiness & minimum temperature

Is Parsley Fern (Cryptogramma crispa)cold hardy? Hardiness zone & min temp

Also called Parsley Fern, Rock Brakes.

More about parsley fern

About Parsley Fern

Cryptogramma crispa · also called Parsley Fern, Rock Brakes · houseplant

Parsley Fern is a distinctive, deciduous to semi-evergreen fern native to acidic mountain screes, rocky slopes, and boulder fields across northern and upland Europe and Asia. Its bright-green, crisply divided fronds closely resemble flat-leaf parsley, giving it its common name. It is notoriously difficult to cultivate, requiring cool temperatures, acid, sharply drained, nutrient-poor substrate, and high ambient humidity — it fails quickly in warm, fertile, or waterlogged conditions. The most important care fact is that it needs consistently cool conditions and must never be grown in alkaline or lime-rich compost. Cryptogramma crispa is not a known toxic species; it is considered mildly-toxic as a precaution due to limited ASPCA data on this genus.

Cold limit: USDA 4-7 · RHS H7 (-25 to 18 °C)

Watch for — Heat stress and collapse: A cool-climate specialist that deteriorates rapidly in temperatures above 20 °C for extended periods. In mild lowland gardens it may persist but rarely thrives; it is best suited to northern England, Scotland, Wales, and equivalent cool, upland climates.

What parsley fern's hardiness rating actually means

Yes — parsley fern is genuinely cold hardy. Rated RHS H7 and USDA 4-7, 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 4-7 — 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. Parsley Fern is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for parsley 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 parsley fern go outside or overwinter — and where?

Plant it out within USDA 4-7 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 parsley fern can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Parsley Fern hardiness — frequently asked questions

Is parsley fern cold hardy?

Yes — parsley fern is genuinely cold hardy. Rated RHS H7 and USDA 4-7, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Parsley Fern is hardy across USDA 4-7; 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 parsley fern can survive?

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

What hardiness zone is parsley fern?

Parsley Fern is rated USDA 4-7 and RHS H7 — Hardy in the severest European continental winters.

Can parsley fern survive winter outside?

Plant it out within USDA 4-7 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 parsley 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.