Cold hardiness & minimum temperature

Is Wall-rue Spleenwort (Asplenium ruta-muraria)cold hardy? Hardiness zone & min temp

Also called Wall-rue Spleenwort, Wall Rue, Wall-rue.

More about wall-rue spleenwort

About Wall-rue Spleenwort

Asplenium ruta-muraria · also called Wall-rue Spleenwort, Wall Rue · houseplant

Asplenium ruta-muraria is a diminutive, evergreen, slow-growing fern native throughout the British Isles, Europe, Asia, and parts of North America, where it colonises the mortar joints of old limestone walls and natural rock crevices. Its tiny, branched fronds — resembling the herb rue in outline — grow to just 4–17 cm and form tight tufts in alkaline, well-drained conditions that would defeat most ferns. The single most important care note is that it requires an alkaline substrate and excellent drainage; it will quickly decline in acidic, waterlogged soil. It is generally considered non-toxic to pets, though it is not individually listed by ASPCA.

Cold limit: USDA 5-9 · RHS H5 (-20 to 25°C)

What wall-rue spleenwort's hardiness rating actually means

Yes — wall-rue spleenwort is genuinely cold hardy. Rated RHS H5 and USDA 5-9, 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 — 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. Wall-rue Spleenwort is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for wall-rue spleenwort 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 wall-rue spleenwort go outside or overwinter — and where?

Plant it out within USDA 5-9 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 wall-rue spleenwort can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Wall-rue Spleenwort hardiness — frequently asked questions

Is wall-rue spleenwort cold hardy?

Yes — wall-rue spleenwort is genuinely cold hardy. Rated RHS H5 and USDA 5-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Wall-rue Spleenwort is hardy across USDA 5-9; 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 wall-rue spleenwort can survive?

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

What hardiness zone is wall-rue spleenwort?

Wall-rue Spleenwort is rated USDA 5-9 and RHS H5 — Hardy in most of the UK and in cold winters.

Can wall-rue spleenwort survive winter outside?

Plant it out within USDA 5-9 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 wall-rue spleenwort 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.