Cold hardiness & minimum temperature

Is Anderson's Holly Fern (Polystichum andersonii)cold hardy? Hardiness zone & min temp

Also called Anderson's Holly Fern, Anderson's Sword Fern.

More about anderson's holly fern

About Anderson's Holly Fern

Polystichum andersonii · also called Anderson's Holly Fern, Anderson's Sword Fern · flowering

Anderson's holly fern, Polystichum andersonii, is an evergreen sword fern native to the moist coniferous forests of north-western North America. It bears arching, lance-shaped fronds of glossy, leathery, twice-cut pinnae and often produces a small bulbil near the frond tip that can root into new plants. A handsome, shade-loving fern for cool woodland gardens.

Cold limit: USDA 5-8 (evergreen, cold-hardy) · RHS H5 (8-21°C)

Watch for — Winter frond tatter: Old fronds can look tired by late winter. Cut them back as new croziers emerge in spring to refresh the clump.

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

Yes — anderson's holly fern is genuinely cold hardy. Rated RHS H5 and USDA 5-8 (evergreen, cold-hardy), 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 5-8 (evergreen, cold-hardy) — 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. Anderson's Holly Fern is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for anderson'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 anderson's holly fern go outside or overwinter — and where?

Plant it out within USDA 5-8 (evergreen, cold-hardy) 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 anderson'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.

Anderson's Holly Fern hardiness — frequently asked questions

Is anderson's holly fern cold hardy?

Yes — anderson's holly fern is genuinely cold hardy. Rated RHS H5 and USDA 5-8 (evergreen, cold-hardy), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Anderson's Holly Fern is hardy across USDA 5-8 (evergreen, cold-hardy); 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 anderson's holly fern can survive?

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

What hardiness zone is anderson's holly fern?

Anderson's Holly Fern is rated USDA 5-8 (evergreen, cold-hardy) and RHS H5 — Hardy in most of the UK and in cold winters.

Can anderson's holly fern survive winter outside?

Plant it out within USDA 5-8 (evergreen, cold-hardy) 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 anderson'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.