Cold hardiness & minimum temperature

Is Rose Grass (Rhodohypoxis baurii)cold hardy? Hardiness zone & min temp

Also called Rose Grass, Red Star.

More about rose grass

About Rose Grass

Rhodohypoxis baurii · also called Rose Grass, Red Star · flowering

Rhodohypoxis baurii is a compact South African alpine bulb producing a long succession of star-shaped pink, red, or white flowers from late spring through summer. It thrives in gritty, perfectly drained soil and demands a dry winter dormancy. Ideal for rock gardens, troughs, or alpine house cultivation in cooler climates.

Cold limit: USDA 7–9 · RHS H4 (5–25°C)

Watch for — Corm rot in winter: The most common cause of plant loss. Wet soil during dormancy causes rapid rot of the corms. Ensure near-dry conditions from autumn through late winter and use perfectly draining gritty compost.

What rose grass's hardiness rating actually means

Yes — rose grass is genuinely cold hardy. Rated RHS H4 and USDA 7–9, 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 7–9 — 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. Rose Grass is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for rose grass 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 rose grass go outside or overwinter — and where?

Plant it out within USDA 7–9 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 rose grass can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H4 figure above.

Rose Grass hardiness — frequently asked questions

Is rose grass cold hardy?

Yes — rose grass is genuinely cold hardy. Rated RHS H4 and USDA 7–9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Rose Grass is hardy across USDA 7–9; 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 rose grass can survive?

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

What hardiness zone is rose grass?

Rose Grass is rated USDA 7–9 and RHS H4 — Hardy in an average winter across much of the temperate world.

Can rose grass survive winter outside?

Plant it out within USDA 7–9 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 rose grass 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.