Cold hardiness & minimum temperature

Is Common Cordgrass (Spartina anglica)cold hardy? Hardiness zone & min temp

Also called Common cordgrass, English cordgrass, Rice grass.

More about common cordgrass

About Common Cordgrass

Spartina anglica · also called Common cordgrass, English cordgrass · flowering

Spartina anglica is an allotetraploid hybrid perennial grass that originated in southern England in the 19th century and is now a dominant pioneer of intertidal mudflats and saltmarshes worldwide. It thrives in waterlogged, saline, anaerobic mud in the intertidal zone and is exceptional among flowering plants in tolerating daily tidal submersion. The most critical care fact is that it requires intertidal, brackish or saline substrate and standing, saline water for establishment — it is a specialist mud-flat coloniser, not a garden plant. Common cordgrass is not listed as toxic by the ASPCA and is considered non-toxic to pets.

Cold limit: USDA 5-9 · RHS H6 (-10 to 30°C)

What common cordgrass's hardiness rating actually means

Yes — common cordgrass 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. Common Cordgrass is built for winter — once established it takes hard frost and snow in its stride.

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

Common Cordgrass hardiness — frequently asked questions

Is common cordgrass cold hardy?

Yes — common cordgrass 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. Common Cordgrass 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 common cordgrass can survive?

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

What hardiness zone is common cordgrass?

Common Cordgrass is rated USDA 5-9 and RHS H6 — Hardy throughout the UK and northern Europe.

Can common cordgrass 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 common cordgrass 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.