Cold hardiness & minimum temperature

Is Korean Mint (Agastache rugosa)cold hardy? Hardiness zone & min temp

Also called Korean mint, blue licorice, wrinkled giant hyssop.

More about korean mint

About Korean Mint

Agastache rugosa · also called Korean mint, blue licorice · herb

Korean mint is an upright, aromatic perennial in the mint family with anise-licorice-scented leaves and tall spikes of purple-blue flowers that draw bees and butterflies. Used as a culinary and medicinal herb across East Asia, it thrives in full sun and well-drained soil, is fairly drought-tolerant once established, and self-seeds readily in the garden.

Cold limit: USDA 4-9 (hardy perennial) · RHS H5 (-5 to 30°C)

Watch for — Winter wet rot: Cold, soggy soil kills the crown over winter more often than cold itself; ensure sharp drainage or grow in raised beds and pots.

What korean mint's hardiness rating actually means

Yes — korean mint is genuinely cold hardy. Rated RHS H5 and USDA 4-9 (hardy perennial), 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 (hardy perennial) — 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. Korean Mint is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for korean mint 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 korean mint go outside or overwinter — and where?

Plant it out within USDA 4-9 (hardy perennial) 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 korean mint can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Korean Mint hardiness — frequently asked questions

Is korean mint cold hardy?

Yes — korean mint is genuinely cold hardy. Rated RHS H5 and USDA 4-9 (hardy perennial), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Korean Mint is hardy across USDA 4-9 (hardy perennial); 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 korean mint can survive?

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

What hardiness zone is korean mint?

Korean Mint is rated USDA 4-9 (hardy perennial) and RHS H5 — Hardy in most of the UK and in cold winters.

Can korean mint survive winter outside?

Plant it out within USDA 4-9 (hardy perennial) 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 korean mint 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.