Cold hardiness & minimum temperature

Is Clematis 'Rouge Cardinal' (Clematis 'Rouge Cardinal')cold hardy? Hardiness zone & min temp

Also called Rouge Cardinal clematis, Red Cardinal clematis.

More about clematis 'rouge cardinal'

About Clematis 'Rouge Cardinal'

Clematis 'Rouge Cardinal' · also called Rouge Cardinal clematis, Red Cardinal clematis · flowering

Clematis 'Rouge Cardinal' is a Group 3 large-flowered clematis bearing rich velvety crimson-red blooms with cream anthers from midsummer into autumn. An outstanding climber for trellis, pergola, or growing through shrubs. Hard-pruning in late winter keeps it vigorous and compact. Toxic to pets and humans if ingested.

Cold limit: USDA 4-9 · RHS H6 (-15 to 25°C)

Watch for — Poor flowering: Usually caused by incorrect pruning (cutting back too late or too early), incorrect planting depth, or insufficient sun. Plant deep (15 cm below the crown), prune hard in late winter, and ensure adequate sun.

What clematis 'rouge cardinal''s hardiness rating actually means

Yes — clematis 'rouge cardinal' is genuinely cold hardy. Rated RHS H6 and USDA 4-9, 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 4-9 — 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. Clematis 'Rouge Cardinal' is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for clematis 'rouge cardinal' 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 clematis 'rouge cardinal' go outside or overwinter — and where?

Plant it out within USDA 4-9 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 clematis 'rouge cardinal' can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Clematis 'Rouge Cardinal' hardiness — frequently asked questions

Is clematis 'rouge cardinal' cold hardy?

Yes — clematis 'rouge cardinal' is genuinely cold hardy. Rated RHS H6 and USDA 4-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Clematis 'Rouge Cardinal' is hardy across USDA 4-9; 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 clematis 'rouge cardinal' can survive?

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

What hardiness zone is clematis 'rouge cardinal'?

Clematis 'Rouge Cardinal' is rated USDA 4-9 and RHS H6 — Hardy throughout the UK and northern Europe.

Can clematis 'rouge cardinal' survive winter outside?

Plant it out within USDA 4-9 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 clematis 'rouge cardinal' 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.