Cold hardiness & minimum temperature

Is Great Masterwort (Astrantia major)cold hardy? Hardiness zone & min temp

Also called Great Masterwort, Greater Masterwort, Masterwort.

More about great masterwort

About Great Masterwort

Astrantia major · also called Great Masterwort, Greater Masterwort · flowering

Astrantia major is a clump-forming herbaceous perennial native to mountain meadows and open woodland in central and eastern Europe, prized for its intricate pincushion flower heads surrounded by papery bracts in shades of white, pink, and deep red from late spring through summer. It performs best in moisture-retentive, humus-rich soil in partial shade or dappled sun, and wilts and goes dormant early if soil dries out. The key care fact is to keep the soil consistently moist — mulching heavily in spring retains moisture and is the single biggest contributor to a long flowering season. Astrantia major has no toxic effects reported and is not listed by the ASPCA as a toxic plant.

Cold limit: USDA 4-7 · RHS H7 (-20 to 22°C)

What great masterwort's hardiness rating actually means

Yes — great masterwort is genuinely cold hardy. Rated RHS H7 and USDA 4-7, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H7 means: Hardy in the severest European continental winters. 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 below about −20 °C. Great Masterwort is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for great masterwort as it gets too cold:

It tolerates winter lows to about −20 °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 great masterwort 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 great masterwort can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Great Masterwort hardiness — frequently asked questions

Is great masterwort cold hardy?

Yes — great masterwort is genuinely cold hardy. Rated RHS H7 and USDA 4-7, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Great Masterwort 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 great masterwort can survive?

Minimum survivable temperature is roughly below about −20 °C. Great Masterwort is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is great masterwort?

Great Masterwort is rated USDA 4-7 and RHS H7 — Hardy in the severest European continental winters.

Can great masterwort 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 great masterwort below its minimum temperature?

It tolerates winter lows to about −20 °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.