Cold hardiness & minimum temperature

Is Winter Aconite (Eranthis hyemalis)cold hardy? Hardiness zone & min temp

Also called Winter aconite, Winter hellebore.

More about winter aconite

About Winter Aconite

Eranthis hyemalis · also called Winter aconite, Winter hellebore · flowering

Native to woodland and scrub in south-east France, Italy, and the Balkans eastward to Bulgaria, Eranthis hyemalis is one of the earliest spring-flowering bulbs, producing bright yellow, buttercup-like flowers surrounded by a ruff of deeply cut green bracts as early as January or February. It naturalises freely under deciduous trees, spreading by self-seeding, and is best left undisturbed once established. The single most important care point is to plant tubers early, as soon as available, since dry storage causes rapid desiccation. All parts of the plant are toxic to cats and dogs.

Cold limit: USDA 4-7 · RHS H6 (-20 to 18°C)

What winter aconite's hardiness rating actually means

Yes — winter aconite is genuinely cold hardy. Rated RHS H6 and USDA 4-7, 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 4-7 — 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. Winter Aconite is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for winter aconite 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 winter aconite go outside or overwinter — and where?

Plant it out within USDA 4-7 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 winter aconite can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Winter Aconite hardiness — frequently asked questions

Is winter aconite cold hardy?

Yes — winter aconite is genuinely cold hardy. Rated RHS H6 and USDA 4-7, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Winter Aconite is hardy across USDA 4-7; 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 winter aconite can survive?

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

What hardiness zone is winter aconite?

Winter Aconite is rated USDA 4-7 and RHS H6 — Hardy throughout the UK and northern Europe.

Can winter aconite survive winter outside?

Plant it out within USDA 4-7 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 winter aconite 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.