Cold hardiness & minimum temperature

Is Large Bitter-cress (Cardamine amara)cold hardy? Hardiness zone & min temp

Also called Large Bitter-cress, Large Bittercress.

More about large bitter-cress

About Large Bitter-cress

Cardamine amara · also called Large Bitter-cress, Large Bittercress · edible

Cardamine amara is a native European perennial of the mustard family (Brassicaceae), found along the margins of streams, wet meadows, and alder carr in the UK and across temperate Europe, distinctive for its purple (not white) anthers. It prefers constantly wet, humus-rich soil in partial shade and will not tolerate drought. The leaves have an edible, peppery-bitter watercress-like flavour and can be used raw or cooked, but harvest only from uncontaminated, clean-water sites. No ASPCA data is available for this species; it is classified as mildly-toxic as a precaution since Brassicaceae plants contain glucosinolates that can cause mild gastrointestinal irritation in pets.

Cold limit: USDA 4-7 · RHS H5 (-15°C to 22°C)

What large bitter-cress's hardiness rating actually means

Yes — large bitter-cress is genuinely cold hardy. Rated RHS H5 and USDA 4-7, 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 4-7 — 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. Large Bitter-cress is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for large bitter-cress 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 large bitter-cress go outside or overwinter — and where?

Plant it out within USDA 4-7 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 large bitter-cress can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Large Bitter-cress hardiness — frequently asked questions

Is large bitter-cress cold hardy?

Yes — large bitter-cress is genuinely cold hardy. Rated RHS H5 and USDA 4-7, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Large Bitter-cress is hardy across USDA 4-7; 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 large bitter-cress can survive?

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

What hardiness zone is large bitter-cress?

Large Bitter-cress is rated USDA 4-7 and RHS H5 — Hardy in most of the UK and in cold winters.

Can large bitter-cress survive winter outside?

Plant it out within USDA 4-7 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 large bitter-cress 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.