Cold hardiness & minimum temperature

Is Hardy Ice Plant (Delosperma cooperi)cold hardy? Hardiness zone & min temp

Also called Hardy Ice Plant, Cooper's Ice Plant, Purple Ice Plant, Trailing Ice Plant.

More about hardy ice plant

About Hardy Ice Plant

Delosperma cooperi · also called Hardy Ice Plant, Cooper's Ice Plant · flowering

The most cold-hardy of the ice plants, this prostrate South African succulent smothers itself in vivid neon purple-pink daisy-like flowers all summer and into autumn. A fast-spreading mat-former at just 7–10 cm tall, it is excellent for rockeries, wall crevices, and sunny slopes. More frost-tolerant than other Delosperma, surviving to USDA Zone 6 with good drainage.

Cold limit: USDA 6–10 · RHS H4 (-15–35°C)

Watch for — Winter crown rot: The leading cause of plant death in the UK. Wet, cold conditions in heavy or poorly drained soil cause the crown to rot at soil level. Ensure very sharp drainage, avoid clay soils entirely, and consider a layer of grit around the crown as a collar. Container plants are most vulnerable if left in waterlogged compost.

What hardy ice plant's hardiness rating actually means

Yes — hardy ice plant is genuinely cold hardy. Rated RHS H4 and USDA 6–10, 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 6–10 — 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. Hardy Ice Plant is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for hardy ice plant 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 hardy ice plant go outside or overwinter — and where?

Plant it out within USDA 6–10 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 hardy ice plant can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H4 figure above.

Hardy Ice Plant hardiness — frequently asked questions

Is hardy ice plant cold hardy?

Yes — hardy ice plant is genuinely cold hardy. Rated RHS H4 and USDA 6–10, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Hardy Ice Plant is hardy across USDA 6–10; 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 hardy ice plant can survive?

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

What hardiness zone is hardy ice plant?

Hardy Ice Plant is rated USDA 6–10 and RHS H4 — Hardy in an average winter across much of the temperate world.

Can hardy ice plant survive winter outside?

Plant it out within USDA 6–10 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 hardy ice plant 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.