Cold hardiness & minimum temperature

Is Walking Fern (Asplenium rhizophyllum)cold hardy? Hardiness zone & min temp

Also called Walking Fern, Walking Spleenwort.

More about walking fern

About Walking Fern

Asplenium rhizophyllum · also called Walking Fern, Walking Spleenwort · houseplant

Walking fern is a small evergreen spleenwort with long, tapering, arrow-shaped fronds that root where their tips touch soil, forming new plantlets that appear to walk across the ground. Native to shaded limestone rocks in eastern North America, it thrives in cool, humid, low-light terrariums on moist, alkaline, gritty substrate and stays under 15 cm tall.

Cold limit: USDA 4-8 (hardy outdoors in shaded rock gardens; grown as a cool terrarium plant indoors) · RHS H5 (10-21°C)

What walking fern's hardiness rating actually means

Yes — walking fern is genuinely cold hardy. Rated RHS H5 and USDA 4-8 (hardy outdoors in shaded rock gardens; grown as a cool terrarium plant indoors), 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 4-8 (hardy outdoors in shaded rock gardens; grown as a cool terrarium plant indoors) — 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. Walking Fern is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for walking 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 walking fern go outside or overwinter — and where?

Plant it out within USDA 4-8 (hardy outdoors in shaded rock gardens; grown as a cool terrarium plant indoors) 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 walking fern can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Walking Fern hardiness — frequently asked questions

Is walking fern cold hardy?

Yes — walking fern is genuinely cold hardy. Rated RHS H5 and USDA 4-8 (hardy outdoors in shaded rock gardens; grown as a cool terrarium plant indoors), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Walking Fern is hardy across USDA 4-8 (hardy outdoors in shaded rock gardens; grown as a cool terrarium plant indoors); 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 walking fern can survive?

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

What hardiness zone is walking fern?

Walking Fern is rated USDA 4-8 (hardy outdoors in shaded rock gardens; grown as a cool terrarium plant indoors) and RHS H5 — Hardy in most of the UK and in cold winters.

Can walking fern survive winter outside?

Plant it out within USDA 4-8 (hardy outdoors in shaded rock gardens; grown as a cool terrarium plant indoors) 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 walking 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.