Cold hardiness & minimum temperature

Is Rough Chervil (Chaerophyllum temulum)cold hardy? Hardiness zone & min temp

Also called Rough Chervil, Rough Cow Parsley.

More about rough chervil

About Rough Chervil

Chaerophyllum temulum · also called Rough Chervil, Rough Cow Parsley · flowering

Rough chervil is a native British and European biennial of hedgerows, roadsides, and woodland edges, belonging to the carrot family (Apiaceae). It produces flat-topped clusters of tiny white flowers from May to July atop stiff, purple-spotted, hairy stems that are distinctively swollen below each leaf node — a key identification feature that separates it from edible umbellifers. The single most important care fact is that it is toxic to people and animals if ingested: it must never be confused with edible parsley, chervil, or cow parsley. It is toxic and must be kept away from pets.

Cold limit: USDA 5-9 · RHS H6 (-15°C to 22°C)

What rough chervil's hardiness rating actually means

Yes — rough chervil is genuinely cold hardy. Rated RHS H6 and USDA 5-9, 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 5-9 — 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. Rough Chervil is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for rough chervil 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 rough chervil go outside or overwinter — and where?

Plant it out within USDA 5-9 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 rough chervil can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Rough Chervil hardiness — frequently asked questions

Is rough chervil cold hardy?

Yes — rough chervil is genuinely cold hardy. Rated RHS H6 and USDA 5-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Rough Chervil is hardy across USDA 5-9; 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 rough chervil can survive?

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

What hardiness zone is rough chervil?

Rough Chervil is rated USDA 5-9 and RHS H6 — Hardy throughout the UK and northern Europe.

Can rough chervil survive winter outside?

Plant it out within USDA 5-9 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 rough chervil 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.