Cold hardiness & minimum temperature

Is Hart's Tongue Fern (Asplenium scolopendrium)cold hardy? Hardiness zone & min temp

Also called Hart's-tongue fern.

More about hart's tongue fern

About Hart's Tongue Fern

Asplenium scolopendrium · also called Hart's-tongue fern · houseplant

Hart's tongue fern stands out among ferns for its undivided, strap-shaped, glossy bright-green fronds with crinkled or wavy margins. A hardy European woodland and wall species, it favours cool, shaded, lime-rich spots and brings bold, leathery texture indoors or in a shady garden corner. Reverse herringbone spore lines stripe the frond undersides.

Cold limit: USDA 5-9 (hardy outdoors; grown indoors in cool rooms) · RHS H6 (10-21°C)

Watch for — Crown or rhizome rot: Cold, waterlogged soil rots the crown. Improve drainage and ease back on water in winter.

What hart's tongue fern's hardiness rating actually means

Yes — hart's tongue fern is genuinely cold hardy. Rated RHS H6 and USDA 5-9 (hardy outdoors; grown indoors in cool rooms), it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H6 means: Hardy throughout the UK and northern Europe. On the US scale that maps to USDA 5-9 (hardy outdoors; grown indoors in cool rooms) — 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 −20 to −15 °C. Hart's Tongue Fern is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for hart's tongue fern as it gets too cold:

It tolerates winter lows to about −20 to −15 °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 hart's tongue fern go outside or overwinter — and where?

Plant it out within USDA 5-9 (hardy outdoors; grown indoors in cool rooms) 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 hart's tongue fern can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Hart's Tongue Fern hardiness — frequently asked questions

Is hart's tongue fern cold hardy?

Yes — hart's tongue fern is genuinely cold hardy. Rated RHS H6 and USDA 5-9 (hardy outdoors; grown indoors in cool rooms), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Hart's Tongue Fern is hardy across USDA 5-9 (hardy outdoors; grown indoors in cool rooms); 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 hart's tongue fern can survive?

Minimum survivable temperature is roughly about −20 to −15 °C. Hart's Tongue Fern is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is hart's tongue fern?

Hart's Tongue Fern is rated USDA 5-9 (hardy outdoors; grown indoors in cool rooms) and RHS H6 — Hardy throughout the UK and northern Europe.

Can hart's tongue fern survive winter outside?

Plant it out within USDA 5-9 (hardy outdoors; grown indoors in cool rooms) 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 hart's tongue fern below its minimum temperature?

It tolerates winter lows to about −20 to −15 °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.