Cold hardiness & minimum temperature

Is Fortune's Holly Fern (Cyrtomium fortunei)cold hardy? Hardiness zone & min temp

Also called Fortune's Holly Fern, Fortune's Cold Hardy Holly Fern, Hardy Japanese Holly Fern.

More about fortune's holly fern

About Fortune's Holly Fern

Cyrtomium fortunei · also called Fortune's Holly Fern, Fortune's Cold Hardy Holly Fern · houseplant

Cyrtomium fortunei is an evergreen to semi-evergreen fern native to eastern Asia and the most cold-hardy member of the holly fern group, surviving outdoor winters where Cyrtomium falcatum would perish. Its matt-green pinnate fronds are slightly narrower and paler than those of Japanese holly fern, with a less glossy surface. It grows best in humus-rich, moist but free-draining soil in partial to full shade, and benefits from some calcium in the soil — strongly acidic conditions can cause yellowing. The single most important care fact is good drainage; root rot from wet winter soils is the chief risk. Toxicity to cats and dogs has not been individually assessed by the ASPCA for this species; treat cautiously.

Cold limit: USDA 6–9 · RHS H5 (-15–25 °C)

Watch for — Winter crown rot: Cold, waterlogged soil in winter is the most common killer, causing the crown to rot from below. Plant in raised beds or on a slope to encourage drainage, and apply a thick layer of grit around the crown before frost arrives.

What fortune's holly fern's hardiness rating actually means

Yes — fortune's holly fern is genuinely cold hardy. Rated RHS H5 and USDA 6–9, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H5 means: Hardy in most of the UK and in cold winters. On the US scale that maps to USDA 6–9 — 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 −15 to −10 °C. Fortune's Holly Fern is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for fortune's holly fern as it gets too cold:

It tolerates winter lows to about −15 to −10 °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 fortune's holly fern go outside or overwinter — and where?

Plant it out within USDA 6–9 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 fortune's holly fern can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Fortune's Holly Fern hardiness — frequently asked questions

Is fortune's holly fern cold hardy?

Yes — fortune's holly fern is genuinely cold hardy. Rated RHS H5 and USDA 6–9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Fortune's Holly Fern is hardy across USDA 6–9; 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 fortune's holly fern can survive?

Minimum survivable temperature is roughly about −15 to −10 °C. Fortune's Holly Fern is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is fortune's holly fern?

Fortune's Holly Fern is rated USDA 6–9 and RHS H5 — Hardy in most of the UK and in cold winters.

Can fortune's holly fern survive winter outside?

Plant it out within USDA 6–9 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 fortune's holly fern below its minimum temperature?

It tolerates winter lows to about −15 to −10 °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.