Cold hardiness & minimum temperature

Is Sempervivum 'Killer' (Sempervivum 'Killer')cold hardy? Hardiness zone & min temp

Also called Killer hens and chicks.

More about sempervivum 'killer'

About Sempervivum 'Killer'

Sempervivum 'Killer' · also called Killer hens and chicks · houseplant

Sempervivum 'Killer' is a vivid hybrid houseleek whose rosettes turn intense red to scarlet in strong sun and cool weather, mellowing to green-bronze in heat or shade. Compact, cold-hardy, and drought-tolerant, it offsets freely into bright colonies. Grown for its dramatic red flush, it needs full sun, gritty fast-draining soil, and a strict soak-and-dry routine.

Cold limit: USDA 4-8 (hardy outdoors; indoors keep cold and very bright) · RHS H6 (-20 to 27°C)

Watch for — Loss of red colour: The scarlet flush depends on full sun, cool temperatures, and lean conditions. In heat, shade, or with feeding the rosettes green over; raise light, reduce fertiliser, and expect summer warmth to soften the colour.

What sempervivum 'killer''s hardiness rating actually means

Yes — sempervivum 'killer' is genuinely cold hardy. Rated RHS H6 and USDA 4-8 (hardy outdoors; indoors keep cold and very bright), 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 4-8 (hardy outdoors; indoors keep cold and very bright) — 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. Sempervivum 'Killer' is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for sempervivum 'killer' 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 sempervivum 'killer' go outside or overwinter — and where?

Plant it out within USDA 4-8 (hardy outdoors; indoors keep cold and very bright) 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 sempervivum 'killer' can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Sempervivum 'Killer' hardiness — frequently asked questions

Is sempervivum 'killer' cold hardy?

Yes — sempervivum 'killer' is genuinely cold hardy. Rated RHS H6 and USDA 4-8 (hardy outdoors; indoors keep cold and very bright), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Sempervivum 'Killer' is hardy across USDA 4-8 (hardy outdoors; indoors keep cold and very bright); 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 sempervivum 'killer' can survive?

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

What hardiness zone is sempervivum 'killer'?

Sempervivum 'Killer' is rated USDA 4-8 (hardy outdoors; indoors keep cold and very bright) and RHS H6 — Hardy throughout the UK and northern Europe.

Can sempervivum 'killer' survive winter outside?

Plant it out within USDA 4-8 (hardy outdoors; indoors keep cold and very bright) 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 sempervivum 'killer' 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.