Cold hardiness & minimum temperature

Is Hyssop (Hyssopus officinalis)cold hardy? Hardiness zone & min temp

Also called hyssop, common hyssop, garden hyssop.

More about hyssop

About Hyssop

Hyssopus officinalis · also called hyssop, common hyssop · herb

Hyssop is a hardy, semi-evergreen Mediterranean sub-shrub in the mint family, grown for its narrow aromatic leaves and spikes of deep blue-purple summer flowers that draw bees and butterflies. It thrives in full sun and sharp drainage, tolerates drought and poor soil, and has a strong, slightly bitter, minty-camphor scent.

Cold limit: USDA 4-9 · RHS H5 (10-27°C)

Watch for — Root rot in wet soil: Heavy or poorly drained ground and overwatering rot the roots. Plant in gritty, free-draining soil and water sparingly, especially over winter.

What hyssop's hardiness rating actually means

Yes — hyssop 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. Hyssop is built for winter — once established it takes hard frost and snow in its stride.

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

Hyssop hardiness — frequently asked questions

Is hyssop cold hardy?

Yes — hyssop 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. Hyssop 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 hyssop can survive?

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

What hardiness zone is hyssop?

Hyssop is rated USDA 4-9 and RHS H5 — Hardy in most of the UK and in cold winters.

Can hyssop 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 hyssop 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.