Cold hardiness & minimum temperature

Is Large-Flowered Houseleek (Sempervivum grandiflorum)cold hardy? Hardiness zone & min temp

Also called Large-flowered Houseleek, Big-flowered Hens and Chicks.

More about large-flowered houseleek

About Large-Flowered Houseleek

Sempervivum grandiflorum · also called Large-flowered Houseleek, Big-flowered Hens and Chicks · flowering

Sempervivum grandiflorum is a distinctive houseleek native to the subalpine and alpine zones of southwestern Switzerland and northwestern Italy, notable for its relatively large, star-shaped flowers with yellowish petals marked with a basal purple spot that appear in summer on stems up to 20 cm tall. Its rosettes reach up to 15 cm in diameter, spreading freely on leafy stolons to form dense mats. Like all houseleeks, it requires full sun and perfectly drained gritty soil, and the mother rosette dies after flowering but is replaced by numerous offsets. Sempervivum is listed as non-toxic to cats and dogs by the ASPCA.

Cold limit: USDA 4-8 · RHS H7 (-34°C to 35°C)

Watch for — Root and crown rot in waterlogged soil: Persistently wet soil, especially in winter, causes Phytophthora and Pythium root rots. Always plant in free-draining grit-based compost; raise beds or use troughs and apply a layer of grit as a surface mulch around the rosette neck.

What large-flowered houseleek's hardiness rating actually means

Yes — large-flowered houseleek is genuinely cold hardy. Rated RHS H7 and USDA 4-8, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H7 means: Hardy in the severest European continental winters. On the US scale that maps to USDA 4-8 — 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 below about −20 °C. Large-Flowered Houseleek is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for large-flowered houseleek as it gets too cold:

It tolerates winter lows to about −20 °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 large-flowered houseleek go outside or overwinter — and where?

Plant it out within USDA 4-8 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 large-flowered houseleek can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Large-Flowered Houseleek hardiness — frequently asked questions

Is large-flowered houseleek cold hardy?

Yes — large-flowered houseleek is genuinely cold hardy. Rated RHS H7 and USDA 4-8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Large-Flowered Houseleek is hardy across USDA 4-8; 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 large-flowered houseleek can survive?

Minimum survivable temperature is roughly below about −20 °C. Large-Flowered Houseleek is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is large-flowered houseleek?

Large-Flowered Houseleek is rated USDA 4-8 and RHS H7 — Hardy in the severest European continental winters.

Can large-flowered houseleek survive winter outside?

Plant it out within USDA 4-8 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 large-flowered houseleek below its minimum temperature?

It tolerates winter lows to about −20 °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.