Cold hardiness & minimum temperature

Is Korean feather reed grass (Calamagrostis brachytricha)cold hardy? Hardiness zone & min temp

Also called Korean feather reed grass, fall-blooming reed grass, diamond grass.

More about korean feather reed grass

About Korean feather reed grass

Calamagrostis brachytricha · also called Korean feather reed grass, fall-blooming reed grass · flowering

Korean feather reed grass is a shade-tolerant cool-season perennial grass prized for its late-season pink-tinged, feathery plumes that open in late summer to autumn — much later than other feather reed grasses. Forming upright, arching clumps, it thrives in part shade and moist soil, offering long interest from its airy flower heads that age to buff and persist through winter.

Cold limit: USDA 4-9 · RHS H7 (-20 to 28°C)

What korean feather reed grass's hardiness rating actually means

Yes — korean feather reed grass is genuinely cold hardy. Rated RHS H7 and USDA 4-9, 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 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 below about −20 °C. Korean feather reed grass is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for korean feather reed grass 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 korean feather reed 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 korean feather reed grass can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Korean feather reed grass hardiness — frequently asked questions

Is korean feather reed grass cold hardy?

Yes — korean feather reed grass is genuinely cold hardy. Rated RHS H7 and USDA 4-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Korean feather reed 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 korean feather reed grass can survive?

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

What hardiness zone is korean feather reed grass?

Korean feather reed grass is rated USDA 4-9 and RHS H7 — Hardy in the severest European continental winters.

Can korean feather reed 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 korean feather reed grass 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.