Cold hardiness & minimum temperature

Is Mouse-ear Hawkweed (Pilosella officinarum)cold hardy? Hardiness zone & min temp

Also called Mouse-ear Hawkweed, Mouse-ear, Hawkweed.

More about mouse-ear hawkweed

About Mouse-ear Hawkweed

Pilosella officinarum · also called Mouse-ear Hawkweed, Mouse-ear · flowering

Pilosella officinarum (syn. Hieracium pilosella) is a low-growing, stoloniferous perennial native to grasslands and dry banks across Europe and the UK, producing solitary lemon-yellow dandelion-like flower heads on hairy scapes from May to August. It thrives in poor, well-drained soils in full sun and actually performs better with minimal fertility — rich soils encourage excessive leaf growth at the expense of flowers. The most important care point is to avoid overwatering, as it is highly susceptible to root rot in wet conditions. It is not listed by the ASPCA as toxic to cats or dogs; use with caution as data is limited.

Cold limit: USDA 3-8 · RHS H7 (-25 to 25 °C)

What mouse-ear hawkweed's hardiness rating actually means

Yes — mouse-ear hawkweed is genuinely cold hardy. Rated RHS H7 and USDA 3-8, 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 3-8 — 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. Mouse-ear Hawkweed is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for mouse-ear hawkweed 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 mouse-ear hawkweed go outside or overwinter — and where?

Plant it out within USDA 3-8 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 mouse-ear hawkweed can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Mouse-ear Hawkweed hardiness — frequently asked questions

Is mouse-ear hawkweed cold hardy?

Yes — mouse-ear hawkweed is genuinely cold hardy. Rated RHS H7 and USDA 3-8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Mouse-ear Hawkweed is hardy across USDA 3-8; 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 mouse-ear hawkweed can survive?

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

What hardiness zone is mouse-ear hawkweed?

Mouse-ear Hawkweed is rated USDA 3-8 and RHS H7 — Hardy in the severest European continental winters.

Can mouse-ear hawkweed survive winter outside?

Plant it out within USDA 3-8 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 mouse-ear hawkweed 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.