Cold hardiness & minimum temperature

Is Six Hills Giant Catmint (Nepeta x faassenii 'Six Hills Giant')cold hardy? Hardiness zone & min temp

Also called Six Hills Giant catmint, tall catmint.

More about six hills giant catmint

About Six Hills Giant Catmint

Nepeta x faassenii 'Six Hills Giant' · also called Six Hills Giant catmint, tall catmint · flowering

Six Hills Giant is the tallest, most vigorous garden catmint, sending up arching stems of grey-green foliage smothered in violet-blue flowers from early summer to autumn. Tougher and bigger than common catmint, it makes a billowing front-of-border drift, edges paths and underplants roses. Bees adore it, and shearing after the first flush guarantees a strong rebloom.

Cold limit: USDA 4-8 (fully hardy perennial outdoors) · RHS H7 (15-27°C)

Watch for — Crown rot in wet sites: Collapse and blackening at the base in poorly drained or winter-wet ground. Plant high in sharply drained soil to keep the crown dry.

What six hills giant catmint's hardiness rating actually means

Yes — six hills giant catmint is genuinely cold hardy. Rated RHS H7 and USDA 4-8 (fully hardy perennial outdoors), 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 4-8 (fully hardy perennial outdoors) — 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. Six Hills Giant Catmint is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for six hills giant catmint 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 six hills giant catmint go outside or overwinter — and where?

Plant it out within USDA 4-8 (fully hardy perennial outdoors) 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 six hills giant catmint can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Six Hills Giant Catmint hardiness — frequently asked questions

Is six hills giant catmint cold hardy?

Yes — six hills giant catmint is genuinely cold hardy. Rated RHS H7 and USDA 4-8 (fully hardy perennial outdoors), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Six Hills Giant Catmint is hardy across USDA 4-8 (fully hardy perennial outdoors); 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 six hills giant catmint can survive?

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

What hardiness zone is six hills giant catmint?

Six Hills Giant Catmint is rated USDA 4-8 (fully hardy perennial outdoors) and RHS H7 — Hardy in the severest European continental winters.

Can six hills giant catmint survive winter outside?

Plant it out within USDA 4-8 (fully hardy perennial outdoors) 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 six hills giant catmint 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.