Cold hardiness & minimum temperature

Is Wild Basil (Clinopodium vulgare)cold hardy? Hardiness zone & min temp

Also called Wild Basil, Cushion Calamint.

More about wild basil

About Wild Basil

Clinopodium vulgare · also called Wild Basil, Cushion Calamint · herb

Wild Basil is a native perennial herb of Europe and western Asia, typically found on dry, chalky grasslands, hedgerows, and scrubby banks. It thrives in free-draining, alkaline soils in full sun to partial shade, and its most important care point is to avoid waterlogged or heavy clay conditions, which quickly cause root rot. Despite sharing a name with culinary basil, it belongs to a different genus and has a mild, aromatic scent but is not used as a kitchen herb. It is considered non-toxic to pets.

Cold limit: USDA 5-9 · RHS H6 (-15 to 25 °C)

What wild basil's hardiness rating actually means

Yes — wild basil 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. Wild Basil is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for wild basil 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 wild basil 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 wild basil can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Wild Basil hardiness — frequently asked questions

Is wild basil cold hardy?

Yes — wild basil 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. Wild Basil 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 wild basil can survive?

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

What hardiness zone is wild basil?

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

Can wild basil 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 wild basil 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.