Cold hardiness & minimum temperature

Is Red Creeping Thyme (Thymus serpyllum 'Coccineus')cold hardy? Hardiness zone & min temp

Also called Red Creeping Thyme, Scarlet Creeping Thyme, Blood-Red Creeping Thyme.

More about red creeping thyme

About Red Creeping Thyme

Thymus serpyllum 'Coccineus' · also called Red Creeping Thyme, Scarlet Creeping Thyme · herb

A mat-forming dwarf thyme producing vivid magenta-red flowers from midsummer, blanketing foliage in colour. Extremely tough and drought-tolerant once established; survives light foot traffic and is excellent for paving joints, rock gardens, and lawn alternatives. Fragrant foliage is edible and attracts pollinators. ASPCA-confirmed non-toxic to cats, dogs, and horses.

Cold limit: USDA 4–9 · RHS H5 (-20–30°C)

What red creeping thyme's hardiness rating actually means

Yes — red creeping thyme is genuinely cold hardy. Rated RHS H5 and USDA 4–9, 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 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 about −15 to −10 °C. Red Creeping Thyme is built for winter — once established it takes hard frost and snow in its stride.

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

Red Creeping Thyme hardiness — frequently asked questions

Is red creeping thyme cold hardy?

Yes — red creeping thyme is genuinely cold hardy. Rated RHS H5 and USDA 4–9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Red Creeping 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 red creeping thyme can survive?

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

What hardiness zone is red creeping thyme?

Red Creeping Thyme is rated USDA 4–9 and RHS H5 — Hardy in most of the UK and in cold winters.

Can red creeping 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 red creeping thyme 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.