Cold hardiness & minimum temperature

Is Ragged Robin (Silene flos-cuculi)cold hardy? Hardiness zone & min temp

Also called Ragged Robin, Meadow Pink, Cuckoo Flower.

More about ragged robin

About Ragged Robin

Silene flos-cuculi · also called Ragged Robin, Meadow Pink · flowering

Silene flos-cuculi (syn. Lychnis flos-cuculi) is a native European perennial wildflower of wet meadows, marshes, and pond margins, prized for its deeply-lobed, ragged-looking pink petals that bloom from late spring through summer. It thrives in consistently moist to boggy soil in full sun or light shade, making it ideal for rain gardens and bog edges; the single most important care fact is to never let the soil dry out. It is not known to be toxic to cats or dogs.

Cold limit: USDA 4-8 · RHS H7 (-20 to 25°C)

What ragged robin's hardiness rating actually means

Yes — ragged robin is genuinely cold hardy. Rated RHS H7 and USDA 4-8, 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 4-8 — 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. Ragged Robin is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for ragged robin 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 ragged robin go outside or overwinter — and where?

Plant it out within USDA 4-8 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 ragged robin can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Ragged Robin hardiness — frequently asked questions

Is ragged robin cold hardy?

Yes — ragged robin is genuinely cold hardy. Rated RHS H7 and USDA 4-8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Ragged Robin is hardy across USDA 4-8; 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 ragged robin can survive?

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

What hardiness zone is ragged robin?

Ragged Robin is rated USDA 4-8 and RHS H7 — Hardy in the severest European continental winters.

Can ragged robin survive winter outside?

Plant it out within USDA 4-8 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 ragged robin 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.