Cold hardiness & minimum temperature

Is Common Fumitory (Fumaria officinalis)cold hardy? Hardiness zone & min temp

Also called Common Fumitory, Earth Smoke, Drug Fumitory.

More about common fumitory

About Common Fumitory

Fumaria officinalis · also called Common Fumitory, Earth Smoke · herb

Common fumitory is a slender summer annual native to Europe and widely naturalised across the UK, where it colonises disturbed arable ground, allotments, and waste places on light, well-drained soils. It produces sprays of pink-tipped tubular flowers from May to September and thrives in open, sunny spots with minimal fertility. The single most important care fact is that it self-seeds freely on bare soil, so deadhead promptly if spread is not wanted. The plant contains isoquinoline alkaloids (protopine, allocryptopine) and is considered mildly toxic if ingested in quantity by pets.

Cold limit: USDA 5-9 · RHS H5 (5–25 °C)

What common fumitory's hardiness rating actually means

Yes — common fumitory is genuinely cold hardy. Rated RHS H5 and USDA 5-9, 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 5-9 — 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 −15 to −10 °C. Common Fumitory is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for common fumitory 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 common fumitory 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 common fumitory can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Common Fumitory hardiness — frequently asked questions

Is common fumitory cold hardy?

Yes — common fumitory is genuinely cold hardy. Rated RHS H5 and USDA 5-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Common Fumitory 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 common fumitory can survive?

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

What hardiness zone is common fumitory?

Common Fumitory is rated USDA 5-9 and RHS H5 — Hardy in most of the UK and in cold winters.

Can common fumitory 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 common fumitory 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.