Cold hardiness & minimum temperature

Is Coast Rock Cress (Arabis blepharophylla)cold hardy? Hardiness zone & min temp

Also called Coast Rock Cress, California Rock Cress, Rose Rock Cress.

More about coast rock cress

About Coast Rock Cress

Arabis blepharophylla · also called Coast Rock Cress, California Rock Cress · flowering

A compact, clump-forming perennial endemic to coastal bluffs of central California, celebrated for its unusual deep rose-pink to magenta flowers in late winter to early spring. Unlike most Arabis, it prefers mild coastal conditions without hard frost. An excellent choice for rock gardens, containers, and sunny banks in mild climates.

Cold limit: USDA 7–10 · RHS H4 (-5 to 22°C)

Watch for — Aphid infestations on new spring growth: New growth in late winter and spring can attract aphid colonies. Blast off with a strong jet of water or apply insecticidal soap spray. Natural predators (ladybirds, lacewings) are usually effective outdoors.

What coast rock cress's hardiness rating actually means

Yes — coast rock cress is genuinely cold hardy. Rated RHS H4 and USDA 7–10, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H4 means: Hardy in an average winter across much of the temperate world. On the US scale that maps to USDA 7–10 — 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 −10 to −5 °C. Coast Rock Cress is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for coast rock cress as it gets too cold:

It tolerates winter lows to about −10 to −5 °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 coast rock cress go outside or overwinter — and where?

Plant it out within USDA 7–10 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 coast rock cress can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H4 figure above.

Coast Rock Cress hardiness — frequently asked questions

Is coast rock cress cold hardy?

Yes — coast rock cress is genuinely cold hardy. Rated RHS H4 and USDA 7–10, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Coast Rock Cress is hardy across USDA 7–10; 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 coast rock cress can survive?

Minimum survivable temperature is roughly about −10 to −5 °C. Coast Rock Cress is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is coast rock cress?

Coast Rock Cress is rated USDA 7–10 and RHS H4 — Hardy in an average winter across much of the temperate world.

Can coast rock cress survive winter outside?

Plant it out within USDA 7–10 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 coast rock cress below its minimum temperature?

It tolerates winter lows to about −10 to −5 °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.