Cold hardiness & minimum temperature

Is Geneva Bugle (Ajuga genevensis)cold hardy? Hardiness zone & min temp

Also called Geneva Bugle, Blue Bugle, Upright Bugle.

More about geneva bugle

About Geneva Bugle

Ajuga genevensis · also called Geneva Bugle, Blue Bugle · flowering

Geneva Bugle is a non-stoloniferous, clump-forming species with erect, hairy stems and vivid blue flower spikes in late spring. Unlike Ajuga reptans, it does not spread by runners, making it far less invasive and better suited to mixed borders. Native to central European grasslands, it thrives in well-drained, sunny to partially shaded positions.

Cold limit: USDA 3–9 · RHS H7 (-25°C to 32°C)

What geneva bugle's hardiness rating actually means

Yes — geneva bugle is genuinely cold hardy. Rated RHS H7 and USDA 3–9, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H7 means: Hardy in the severest European continental winters. On the US scale that maps to USDA 3–9 — 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 below about −20 °C. Geneva Bugle is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for geneva bugle as it gets too cold:

It tolerates winter lows to about −20 °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 geneva bugle go outside or overwinter — and where?

Plant it out within USDA 3–9 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 geneva bugle can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Geneva Bugle hardiness — frequently asked questions

Is geneva bugle cold hardy?

Yes — geneva bugle is genuinely cold hardy. Rated RHS H7 and USDA 3–9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Geneva Bugle is hardy across USDA 3–9; 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 geneva bugle can survive?

Minimum survivable temperature is roughly below about −20 °C. Geneva Bugle is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is geneva bugle?

Geneva Bugle is rated USDA 3–9 and RHS H7 — Hardy in the severest European continental winters.

Can geneva bugle survive winter outside?

Plant it out within USDA 3–9 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 geneva bugle below its minimum temperature?

It tolerates winter lows to about −20 °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.