Cold hardiness & minimum temperature

Is Agastache 'Blue Fortune' (Agastache 'Blue Fortune')cold hardy? Hardiness zone & min temp

Also called Blue Fortune hyssop, Anise hyssop.

More about agastache 'blue fortune'

About Agastache 'Blue Fortune'

Agastache 'Blue Fortune' · also called Blue Fortune hyssop, Anise hyssop · flowering

A robust, award-winning anise hyssop hybrid (A. foeniculum x rugosa) topped from midsummer into autumn with dense, powder-blue bottlebrush flower spikes. The anise-scented foliage is loved by bees and butterflies and shunned by deer. More cold- and wet-tolerant than most Agastache, this upright, sterile-flowered perennial blooms for months and makes a magnet for pollinators in sunny borders.

Cold limit: USDA 5-9 · RHS H6 (-1 to 30°C active growth (hardy to about -23°C dormant))

Watch for — Root rot in wet winters: Soggy winter soil is the main killer. Plant in sharply drained ground; add grit to heavy clay.

What agastache 'blue fortune''s hardiness rating actually means

Yes — agastache 'blue fortune' is genuinely cold hardy. Rated RHS H6 and USDA 5-9, 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 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 −20 to −15 °C. Agastache 'Blue Fortune' is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for agastache 'blue fortune' 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 agastache 'blue fortune' 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 agastache 'blue fortune' can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Agastache 'Blue Fortune' hardiness — frequently asked questions

Is agastache 'blue fortune' cold hardy?

Yes — agastache 'blue fortune' is genuinely cold hardy. Rated RHS H6 and USDA 5-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Agastache 'Blue Fortune' 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 agastache 'blue fortune' can survive?

Minimum survivable temperature is roughly about −20 to −15 °C. Agastache 'Blue Fortune' is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is agastache 'blue fortune'?

Agastache 'Blue Fortune' is rated USDA 5-9 and RHS H6 — Hardy throughout the UK and northern Europe.

Can agastache 'blue fortune' 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 agastache 'blue fortune' 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.