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 Shield Fern.

More about anderson's holly fern

About Anderson's Holly Fern

Polystichum andersonii · also called Anderson's Holly Fern, Anderson's Shield Fern · houseplant

Native to the Pacific Northwest of North America, Polystichum andersonii is a large, stately evergreen fern that reaches 60–120 cm tall. It forms an upright, shuttlecock-like rosette of glossy, pinnate fronds and uniquely produces bulblets near the frond tips that root where they touch the ground. It thrives in cool, humus-rich, evenly moist soil under part to full shade; the single most important care fact is that it strongly dislikes heat and drought, making it poorly suited to gardens east of the Cascades or to hot summers. Ferns in the genus Polystichum are listed as non-toxic to cats and dogs by the ASPCA.

Cold limit: USDA 6-8 · RHS H5 (-15 to 25°C)

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

Yes — anderson's holly fern is genuinely cold hardy. Rated RHS H5 and USDA 6-8, 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 6-8 — 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 6-8 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 6-8, 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 6-8; 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 6-8 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 6-8 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.