Cold hardiness & minimum temperature

Is Yokosuka Lady Fern (Athyrium yokoscense)cold hardy? Hardiness zone & min temp

Also called Yokosuka Lady Fern, Asian Common Lady Fern, Hebino-negoza.

More about yokosuka lady fern

About Yokosuka Lady Fern

Athyrium yokoscense · also called Yokosuka Lady Fern, Asian Common Lady Fern · houseplant

Athyrium yokoscense is a compact, deciduous lady fern native to Japan, Korea, and eastern China, well known in ecological research for its exceptional tolerance of soils contaminated with heavy metals such as zinc, lead, cadmium, and copper — making it uniquely useful for phytoremediation plantings. In the garden it forms a tidy clump of finely divided fronds reaching around 30 cm tall, preferring cool shade and consistently moist conditions. The single most important care note is that it demands reliable moisture and shelter; it is not suited to sunny or dry positions. Its pet-toxicity status is not individually confirmed by ASPCA; as a precaution it is classified as mildly toxic.

Cold limit: USDA 6-9 · RHS H5 (-15 to 25°C)

Watch for — Slug damage to emerging fronds: The soft croziers in spring are vulnerable; apply iron-phosphate-based slug pellets around the crown from late winter as soon as growth begins.

What yokosuka lady fern's hardiness rating actually means

Yes — yokosuka lady fern is genuinely cold hardy. Rated RHS H5 and USDA 6-9, 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 6-9 — 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. Yokosuka Lady Fern is built for winter — once established it takes hard frost and snow in its stride.

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

Plant it out within USDA 6-9 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 yokosuka lady fern can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Yokosuka Lady Fern hardiness — frequently asked questions

Is yokosuka lady fern cold hardy?

Yes — yokosuka lady fern is genuinely cold hardy. Rated RHS H5 and USDA 6-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Yokosuka Lady Fern is hardy across USDA 6-9; 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 yokosuka lady fern can survive?

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

What hardiness zone is yokosuka lady fern?

Yokosuka Lady Fern is rated USDA 6-9 and RHS H5 — Hardy in most of the UK and in cold winters.

Can yokosuka lady fern survive winter outside?

Plant it out within USDA 6-9 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 yokosuka lady 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.