Cold hardiness & minimum temperature

Is Red Valerian (Centranthus ruber)cold hardy? Hardiness zone & min temp

Also called red valerian, Jupiter's beard, kiss-me-quick.

More about red valerian

About Red Valerian

Centranthus ruber · also called red valerian, Jupiter's beard · flowering

Centranthus ruber is a fast, free-flowering perennial bearing dense clusters of scented red, pink or white blooms from late spring into autumn. It thrives in poor, alkaline, free-draining soil and full sun, famously colonising walls, gravel and chalk. Easy and pollinator-friendly, it self-seeds enthusiastically and can naturalise aggressively in mild climates.

Cold limit: USDA 5-8 · RHS H5 (-15 to 30°C)

What red valerian's hardiness rating actually means

Yes — red valerian is genuinely cold hardy. Rated RHS H5 and USDA 5-8, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H5 means: Hardy in most of the UK and in cold winters. On the US scale that maps to USDA 5-8 — 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 −15 to −10 °C. Red Valerian is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for red valerian as it gets too cold:

It tolerates winter lows to about −15 to −10 °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 valerian go outside or overwinter — and where?

Plant it out within USDA 5-8 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 valerian can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Red Valerian hardiness — frequently asked questions

Is red valerian cold hardy?

Yes — red valerian is genuinely cold hardy. Rated RHS H5 and USDA 5-8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Red Valerian is hardy across USDA 5-8; 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 valerian can survive?

Minimum survivable temperature is roughly about −15 to −10 °C. Red Valerian is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is red valerian?

Red Valerian is rated USDA 5-8 and RHS H5 — Hardy in most of the UK and in cold winters.

Can red valerian survive winter outside?

Plant it out within USDA 5-8 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 valerian below its minimum temperature?

It tolerates winter lows to about −15 to −10 °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.