Cold hardiness & minimum temperature

Is Athyrium niponicum 'Ursula's Red' (Athyrium niponicum 'Ursula's Red')cold hardy? Hardiness zone & min temp

Also called Ursula's Red Painted Fern.

More about athyrium niponicum 'ursula's red'

About Athyrium niponicum 'Ursula's Red'

Athyrium niponicum 'Ursula's Red' · also called Ursula's Red Painted Fern · flowering

'Ursula's Red' is a vivid Japanese painted fern selection with broad silvery fronds overlaid by deep maroon-red zones radiating from dark central stems. Deciduous and slowly spreading, it offers some of the boldest red colouration in the group. It performs best in cool, moist, humus-rich soil and partial shade, lighting up shaded borders with metallic colour.

Cold limit: USDA 4-9 · RHS H7 (-29 to 24°C)

Watch for — Frost nip on spring croziers: Newly emerging fronds are vulnerable to late frosts. Shelter the plant or fleece it during cold spells; it normally produces fresh fronds afterwards.

What athyrium niponicum 'ursula's red''s hardiness rating actually means

Yes — athyrium niponicum 'ursula's red' is genuinely cold hardy. Rated RHS H7 and USDA 4-9, 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 4-9 — 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 below about −20 °C. Athyrium niponicum 'Ursula's Red' is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for athyrium niponicum 'ursula's red' 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 athyrium niponicum 'ursula's red' go outside or overwinter — and where?

Plant it out within USDA 4-9 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 athyrium niponicum 'ursula's red' can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Athyrium niponicum 'Ursula's Red' hardiness — frequently asked questions

Is athyrium niponicum 'ursula's red' cold hardy?

Yes — athyrium niponicum 'ursula's red' is genuinely cold hardy. Rated RHS H7 and USDA 4-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Athyrium niponicum 'Ursula's Red' is hardy across USDA 4-9; 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 athyrium niponicum 'ursula's red' can survive?

Minimum survivable temperature is roughly below about −20 °C. Athyrium niponicum 'Ursula's Red' is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is athyrium niponicum 'ursula's red'?

Athyrium niponicum 'Ursula's Red' is rated USDA 4-9 and RHS H7 — Hardy in the severest European continental winters.

Can athyrium niponicum 'ursula's red' survive winter outside?

Plant it out within USDA 4-9 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 athyrium niponicum 'ursula's red' 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.