Cold hardiness & minimum temperature

Is Hummingbird Mint (Agastache rupestris)cold hardy? Hardiness zone & min temp

Also called sunset hyssop, hummingbird mint, rock anise hyssop.

More about hummingbird mint

About Hummingbird Mint

Agastache rupestris · also called sunset hyssop, hummingbird mint · herb

Agastache rupestris, sunset hyssop, is an aromatic Southwest US native with fine, threadlike grey-green leaves and slender spikes of smoky-orange flowers with lavender calyces from summer into autumn. Smelling of root beer and mint, it thrives in full sun and sharp drainage, tolerates heat and drought, and draws hummingbirds and bees.

Cold limit: USDA 4-9 · RHS H4 (15-32°C)

Watch for — Winter wet rot: The leading killer; soggy soil in winter rots the crown. Plant in very sharp drainage, on a slope or in a raised gritty bed.

What hummingbird mint's hardiness rating actually means

Yes — hummingbird mint is genuinely cold hardy. Rated RHS H4 and USDA 4-9, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H4 means: Hardy in an average winter across much of the temperate world. 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 −10 to −5 °C. Hummingbird Mint is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for hummingbird mint as it gets too cold:

It tolerates winter lows to about −10 to −5 °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 hummingbird mint 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 hummingbird mint can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H4 figure above.

Hummingbird Mint hardiness — frequently asked questions

Is hummingbird mint cold hardy?

Yes — hummingbird mint is genuinely cold hardy. Rated RHS H4 and USDA 4-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Hummingbird Mint 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 hummingbird mint can survive?

Minimum survivable temperature is roughly about −10 to −5 °C. Hummingbird Mint is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is hummingbird mint?

Hummingbird Mint is rated USDA 4-9 and RHS H4 — Hardy in an average winter across much of the temperate world.

Can hummingbird mint 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 hummingbird mint below its minimum temperature?

It tolerates winter lows to about −10 to −5 °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.