Cold hardiness & minimum temperature

Is Broad-leaved Thyme (Thymus pulegioides)cold hardy? Hardiness zone & min temp

Also called Broad-leaved Thyme, Lemon-scented Thyme, Large Thyme.

More about broad-leaved thyme

About Broad-leaved Thyme

Thymus pulegioides · also called Broad-leaved Thyme, Lemon-scented Thyme · herb

Broad-leaved Thyme is a European native and one of the parents of Thymus × citriodorus. It produces larger, rounder leaves than common thyme with a mild lemon-thyme scent, and forms a low, semi-prostrate sub-shrub useful as a ground cover or herb garden specimen. Hardy and undemanding, it thrives in well-drained, sunny positions.

Cold limit: USDA 4–9 · RHS H6 (-20–28°C)

Watch for — Root rot in heavy soils: On poorly drained sites, particularly in wet winters, root rot develops rapidly. Improve drainage with grit before planting or grow in raised beds. Container plants must have drainage holes and be raised on feet to allow free drainage.

What broad-leaved thyme's hardiness rating actually means

Yes — broad-leaved thyme is genuinely cold hardy. Rated RHS H6 and USDA 4–9, 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 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 −20 to −15 °C. Broad-leaved Thyme is built for winter — once established it takes hard frost and snow in its stride.

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

Broad-leaved Thyme hardiness — frequently asked questions

Is broad-leaved thyme cold hardy?

Yes — broad-leaved thyme is genuinely cold hardy. Rated RHS H6 and USDA 4–9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Broad-leaved 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 broad-leaved thyme can survive?

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

What hardiness zone is broad-leaved thyme?

Broad-leaved Thyme is rated USDA 4–9 and RHS H6 — Hardy throughout the UK and northern Europe.

Can broad-leaved 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 broad-leaved thyme 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.