Cold hardiness & minimum temperature

Is Silver Posie Thyme (Thymus vulgaris 'Silver Posie')cold hardy? Hardiness zone & min temp

Also called Silver Posie Thyme, Silver Thyme, Variegated Thyme.

More about silver posie thyme

About Silver Posie Thyme

Thymus vulgaris 'Silver Posie' · also called Silver Posie Thyme, Silver Thyme · herb

Silver Posie Thyme is a compact, ornamental cultivar of common thyme with attractive silver-edged, cream-and-green variegated foliage. It produces the same aromatic, culinary-quality leaves as the species, with a slightly more delicate flavour, plus pretty pale-pink flowers beloved by bees. Ideal for container herb gardens, edging, and rockeries, it needs full sun and excellent drainage.

Cold limit: USDA 5–9 · RHS H5 (-10–30°C)

What silver posie thyme's hardiness rating actually means

Yes — silver posie thyme 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. Silver Posie Thyme is built for winter — once established it takes hard frost and snow in its stride.

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

Silver Posie Thyme hardiness — frequently asked questions

Is silver posie thyme cold hardy?

Yes — silver posie thyme 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. Silver Posie Thyme 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 silver posie thyme can survive?

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

What hardiness zone is silver posie thyme?

Silver Posie Thyme is rated USDA 5–9 and RHS H5 — Hardy in most of the UK and in cold winters.

Can silver posie thyme 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 silver posie 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.