Cold hardiness & minimum temperature

Is Catlin's Giant Bugle (Ajuga reptans 'Catlin's Giant')cold hardy? Hardiness zone & min temp

Also called Catlin's Giant Bugle, Giant Bugleweed, Carpet Bugle.

More about catlin's giant bugle

About Catlin's Giant Bugle

Ajuga reptans 'Catlin's Giant' · also called Catlin's Giant Bugle, Giant Bugleweed · flowering

A robust, clump-forming groundcover with oversized, deep bronze-purple leaves and tall spikes of violet-blue flowers in spring. Catlin's Giant is prized for its exceptional leaf size — up to 6 inches — making it one of the boldest Ajuga cultivars. Thrives in partial to full shade and suppresses weeds effectively in moist, humus-rich soil.

Cold limit: USDA 3–9 · RHS H7 (-20°C to 30°C)

What catlin's giant bugle's hardiness rating actually means

Yes — catlin's giant 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. Catlin's Giant Bugle is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for catlin's giant 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 catlin's giant 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 catlin's giant bugle can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Catlin's Giant Bugle hardiness — frequently asked questions

Is catlin's giant bugle cold hardy?

Yes — catlin's giant 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. Catlin's Giant 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 catlin's giant bugle can survive?

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

What hardiness zone is catlin's giant bugle?

Catlin's Giant Bugle is rated USDA 3–9 and RHS H7 — Hardy in the severest European continental winters.

Can catlin's giant 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 catlin's giant 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.