Cold hardiness & minimum temperature

Is Bushgrass (Calamagrostis arundinacea)cold hardy? Hardiness zone & min temp

Also called Bushgrass, Reed small-reed, Woodland small-reed.

More about bushgrass

About Bushgrass

Calamagrostis arundinacea · also called Bushgrass, Reed small-reed · flowering

Calamagrostis arundinacea is a widespread ornamental grass native to Europe and Asia, found in woodland margins, scrub, and semi-shaded habitats from western Europe east to Japan. It forms arching clumps of narrow green leaves and produces feathery, purplish-tinted flower panicles in late summer that fade to a warm tan and persist into winter, providing excellent structural interest. It is notably tolerant of dry shade, making it valuable in difficult garden spots under trees. Calamagrostis grasses are not considered toxic to cats or dogs.

Cold limit: USDA 4-9 · RHS H6 (-20 to 35°C)

What bushgrass's hardiness rating actually means

Yes — bushgrass 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. Bushgrass is built for winter — once established it takes hard frost and snow in its stride.

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

Bushgrass hardiness — frequently asked questions

Is bushgrass cold hardy?

Yes — bushgrass 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. Bushgrass 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 bushgrass can survive?

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

What hardiness zone is bushgrass?

Bushgrass is rated USDA 4-9 and RHS H6 — Hardy throughout the UK and northern Europe.

Can bushgrass 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 bushgrass 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.