Cold hardiness & minimum temperature

Is Naomi Hakone Grass (Hakonechloa macra 'Naomi')cold hardy? Hardiness zone & min temp

Also called naomi hakone grass, white-edged hakone grass.

More about naomi hakone grass

About Naomi Hakone Grass

Hakonechloa macra 'Naomi' · also called naomi hakone grass, white-edged hakone grass · flowering

Hakonechloa macra 'Naomi' is a Japanese forest grass with bright gold-and-green variegated blades that take on rosy-red and purple tints in autumn. Its arching, cascading mounds light up shady borders and containers. Like all hakone grasses it favours part shade and rich, consistently moist soil, rewarding patience with a soft, flowing deciduous form.

Cold limit: USDA 5-9 · RHS H6 (-1 to 24°C)

Watch for — Winter dormancy: The plant dies back to ground level each winter and may look dead; cut old foliage in late winter before new shoots emerge in spring.

What naomi hakone grass's hardiness rating actually means

Yes — naomi hakone grass 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. Naomi Hakone Grass is built for winter — once established it takes hard frost and snow in its stride.

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

Naomi Hakone Grass hardiness — frequently asked questions

Is naomi hakone grass cold hardy?

Yes — naomi hakone grass 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. Naomi Hakone Grass 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 naomi hakone grass can survive?

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

What hardiness zone is naomi hakone grass?

Naomi Hakone Grass is rated USDA 5-9 and RHS H6 — Hardy throughout the UK and northern Europe.

Can naomi hakone grass 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 naomi hakone 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.