Cold hardiness & minimum temperature

Is Hook Sedge (Uncinia rubra)cold hardy? Hardiness zone & min temp

Also called red hook sedge, hook grass.

More about hook sedge

About Hook Sedge

Uncinia rubra · also called red hook sedge, hook grass · flowering

Red hook sedge is an evergreen New Zealand sedge prized for its glossy, mahogany-red to bronze blades that form a low, arching tuft. Named for the tiny hooked seeds that cling to fur and clothing, it brings rich colour to borders, gravel gardens and containers. It likes moisture-retentive yet drained soil and good light, and is short-lived but easily renewed.

Cold limit: USDA 6-9 · RHS H4 (-10 to 28°C)

Watch for — Winter scorch: Cold, drying winds can brown the evergreen blades. Provide a sheltered position and comb out damaged foliage in spring.

What hook sedge's hardiness rating actually means

Yes — hook sedge is genuinely cold hardy. Rated RHS H4 and USDA 6-9, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H4 means: Hardy in an average winter across much of the temperate world. On the US scale that maps to USDA 6-9 — 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 −10 to −5 °C. Hook Sedge is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for hook sedge as it gets too cold:

It tolerates winter lows to about −10 to −5 °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 hook sedge go outside or overwinter — and where?

Plant it out within USDA 6-9 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 hook sedge can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H4 figure above.

Hook Sedge hardiness — frequently asked questions

Is hook sedge cold hardy?

Yes — hook sedge is genuinely cold hardy. Rated RHS H4 and USDA 6-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Hook Sedge is hardy across USDA 6-9; 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 hook sedge can survive?

Minimum survivable temperature is roughly about −10 to −5 °C. Hook Sedge is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is hook sedge?

Hook Sedge is rated USDA 6-9 and RHS H4 — Hardy in an average winter across much of the temperate world.

Can hook sedge survive winter outside?

Plant it out within USDA 6-9 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 hook sedge below its minimum temperature?

It tolerates winter lows to about −10 to −5 °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.