Cold hardiness & minimum temperature

Is Wild Thyme (Thymus polytrichus)cold hardy? Hardiness zone & min temp

Also called Wild Thyme, Breckland Thyme, Creeping Wild Thyme.

More about wild thyme

About Wild Thyme

Thymus polytrichus · also called Wild Thyme, Breckland Thyme · herb

Wild thyme is a mat-forming, aromatic, semi-evergreen subshrub native to short, dry grassland, rocky outcrops, cliff-tops, and chalk downland across Europe and into western Asia. It requires full sun and excellent drainage, and is exceptionally drought-tolerant and cold-hardy. The most important care fact is that it cannot tolerate waterlogged or heavy clay soils — sharp drainage is essential for long-term survival. Thymus species are listed by the ASPCA as non-toxic to cats, dogs, and horses.

Cold limit: USDA 4-9 · RHS H7 (-30 to 30°C)

Watch for — Crown rot and die-back in wet winters: The leading cause of loss — standing water around the crown in winter causes fungal rot; plant on a slope, in raised beds, or add a gravel mulch around the crown to shed water.

What wild thyme's hardiness rating actually means

Yes — wild thyme is genuinely cold hardy. Rated RHS H7 and USDA 4-9, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H7 means: Hardy in the severest European continental winters. On the US scale that maps to USDA 4-9 — 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 below about −20 °C. Wild Thyme is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for wild thyme as it gets too cold:

It tolerates winter lows to about −20 °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 thyme go outside or overwinter — and where?

Plant it out within USDA 4-9 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 thyme can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Wild Thyme hardiness — frequently asked questions

Is wild thyme cold hardy?

Yes — wild thyme is genuinely cold hardy. Rated RHS H7 and USDA 4-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Wild Thyme is hardy across USDA 4-9; 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 thyme can survive?

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

What hardiness zone is wild thyme?

Wild Thyme is rated USDA 4-9 and RHS H7 — Hardy in the severest European continental winters.

Can wild thyme survive winter outside?

Plant it out within USDA 4-9 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 thyme below its minimum temperature?

It tolerates winter lows to about −20 °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.