Cold hardiness & minimum temperature

Is Lemon Thyme (Thymus × citriodorus)cold hardy? Hardiness zone & min temp

Also called Lemon Thyme, Citrus Thyme.

More about lemon thyme

About Lemon Thyme

Thymus × citriodorus · also called Lemon Thyme, Citrus Thyme · herb

Lemon Thyme is a hybrid between Thymus vulgaris and Thymus pulegioides, producing a low, mounding sub-shrub with a fresh lemon-thyme scent. Available in green, gold-variegated, and silver-edged forms, it doubles as an ornamental ground cover. Hardy and drought-tolerant once established, it performs best in full sun with sharply drained soil.

Cold limit: USDA 5–9 · RHS H5 (-15–30°C)

Watch for — Root rot in wet soils: This hybrid is less tolerant of wet roots than it appears. Waterlogged conditions in winter are a primary cause of death. Ensure raised beds or very gritty container mixes. In wet climates, plant on a slight slope or in raised rockery pockets.

What lemon thyme's hardiness rating actually means

Yes — lemon 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. Lemon Thyme is built for winter — once established it takes hard frost and snow in its stride.

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

Lemon Thyme hardiness — frequently asked questions

Is lemon thyme cold hardy?

Yes — lemon 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. Lemon 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 lemon thyme can survive?

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

What hardiness zone is lemon thyme?

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

Can lemon 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 lemon 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.