Cold hardiness & minimum temperature

Is Moor Witch Purple Moor Grass (Molinia caerulea 'Moorhexe')cold hardy? Hardiness zone & min temp

Also called Moor witch purple moor grass, Moorhexe purple moor grass, Purple moor grass.

More about moor witch purple moor grass

About Moor Witch Purple Moor Grass

Molinia caerulea 'Moorhexe' · also called Moor witch purple moor grass, Moorhexe purple moor grass · flowering

Molinia caerulea 'Moorhexe' (German: 'moor witch') is a compact, very upright cultivar of purple moor grass, native to the moorlands, bogs, and wet heathlands of Europe and western Asia. Unlike many ornamental grasses, it is a completely deciduous species that collapses and can be cleared away cleanly each winter, leaving no persistent dead thatch. It is prized for its stiffly erect, purple-tinted flowering stems that turn rich amber-yellow in autumn. The most important care point is to provide acid to neutral, reliably moist soil — it dislikes alkaline conditions. Molinia caerulea is not considered toxic to cats or dogs.

Cold limit: USDA 4-9 · RHS H6 (-20 to 30°C)

What moor witch purple moor grass's hardiness rating actually means

Yes — moor witch purple moor grass is genuinely cold hardy. Rated RHS H6 and USDA 4-9, 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 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 −20 to −15 °C. Moor Witch Purple Moor Grass is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for moor witch purple moor grass 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 moor witch purple moor grass 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 moor witch purple moor grass can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Moor Witch Purple Moor Grass hardiness — frequently asked questions

Is moor witch purple moor grass cold hardy?

Yes — moor witch purple moor grass is genuinely cold hardy. Rated RHS H6 and USDA 4-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Moor Witch Purple Moor Grass 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 moor witch purple moor grass can survive?

Minimum survivable temperature is roughly about −20 to −15 °C. Moor Witch Purple Moor Grass is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is moor witch purple moor grass?

Moor Witch Purple Moor Grass is rated USDA 4-9 and RHS H6 — Hardy throughout the UK and northern Europe.

Can moor witch purple moor grass 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 moor witch purple moor grass 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.