Cold hardiness & minimum temperature

Is Autumn Fern 'Brilliance' (Dryopteris erythrosora 'Brilliance')cold hardy? Hardiness zone & min temp

Also called Japanese shield fern, Copper shield fern.

More about autumn fern 'brilliance'

About Autumn Fern 'Brilliance'

Dryopteris erythrosora 'Brilliance' · also called Japanese shield fern, Copper shield fern · houseplant

'Brilliance' is a selection of the autumn fern grown for new fronds that emerge a vivid coppery-orange before maturing to glossy deep green. A semi-evergreen woodland fern from East Asia, it is hardy and easy in shade, holding colour longer than the species. It suits cool rooms, shaded gardens and containers, dying back only in hard winters.

Cold limit: USDA 5-9 (outdoor-hardy; indoors as a cool-room or seasonal fern) · RHS H5 (10-22°C)

Watch for — Tatty old fronds in spring: Winter-damaged evergreen fronds. Cut them back to the crown before the new coppery flush emerges to keep the plant tidy.

What autumn fern 'brilliance''s hardiness rating actually means

Yes — autumn fern 'brilliance' is genuinely cold hardy. Rated RHS H5 and USDA 5-9 (outdoor-hardy; indoors as a cool-room or seasonal fern), 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 5-9 (outdoor-hardy; indoors as a cool-room or seasonal fern) — 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. Autumn Fern 'Brilliance' is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for autumn fern 'brilliance' 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 autumn fern 'brilliance' go outside or overwinter — and where?

Plant it out within USDA 5-9 (outdoor-hardy; indoors as a cool-room or seasonal fern) 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 autumn fern 'brilliance' can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Autumn Fern 'Brilliance' hardiness — frequently asked questions

Is autumn fern 'brilliance' cold hardy?

Yes — autumn fern 'brilliance' is genuinely cold hardy. Rated RHS H5 and USDA 5-9 (outdoor-hardy; indoors as a cool-room or seasonal fern), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Autumn Fern 'Brilliance' is hardy across USDA 5-9 (outdoor-hardy; indoors as a cool-room or seasonal fern); 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 autumn fern 'brilliance' can survive?

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

What hardiness zone is autumn fern 'brilliance'?

Autumn Fern 'Brilliance' is rated USDA 5-9 (outdoor-hardy; indoors as a cool-room or seasonal fern) and RHS H5 — Hardy in most of the UK and in cold winters.

Can autumn fern 'brilliance' survive winter outside?

Plant it out within USDA 5-9 (outdoor-hardy; indoors as a cool-room or seasonal fern) 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 autumn fern 'brilliance' 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.