Cold hardiness & minimum temperature

Is Red Campion (Silene dioica)cold hardy? Hardiness zone & min temp

Also called Red Campion, Red Catchfly, Bachelor's Buttons.

More about red campion

About Red Campion

Silene dioica · also called Red Campion, Red Catchfly · flowering

Silene dioica is a short-lived dioecious perennial or biennial native to woodland edges, hedgerows, and shaded banks across the UK and Europe. It bears vivid rose-pink flowers from late spring through summer and self-seeds freely, maintaining colonies without intervention. The most important care fact is to allow self-seeding or to sow fresh seed each year, as individual plants are relatively short-lived. The plant contains saponins; while not acutely dangerous to cats or dogs in typical garden exposure, it should be treated as mildly toxic as it is not listed on the ASPCA database.

Cold limit: USDA 4-8 · RHS H6 (-20 to 25°C)

What red campion's hardiness rating actually means

Yes — red campion is genuinely cold hardy. Rated RHS H6 and USDA 4-8, 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 4-8 — 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 about −20 to −15 °C. Red Campion is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for red campion 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 red campion 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 red campion can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Red Campion hardiness — frequently asked questions

Is red campion cold hardy?

Yes — red campion is genuinely cold hardy. Rated RHS H6 and USDA 4-8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Red Campion 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 red campion can survive?

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

What hardiness zone is red campion?

Red Campion is rated USDA 4-8 and RHS H6 — Hardy throughout the UK and northern Europe.

Can red campion 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 red campion 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.