Cold hardiness & minimum temperature

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

Also called Black Houseleek.

More about sempervivum 'black'

About Sempervivum 'Black'

Sempervivum 'Black' · also called Black Houseleek · houseplant

Sempervivum 'Black' is a hardy houseleek prized for flat rosettes that deepen to near-black maroon tips over green centres in strong sun and cold, fading toward green in shade. It clusters into offset-filled mats, shrugs off frost and drought, and is monocarpic. A tough, low-care alpine, ASPCA non-toxic to cats and dogs.

Cold limit: USDA 4-8 (hardy alpine; outdoors year-round) · RHS H5 (-20 to 28°C)

Watch for — Colour reverting to green: Too little light. The dark, near-black pigment is sun- and cold-driven and fades fast in low light or warmth.

What sempervivum 'black''s hardiness rating actually means

Yes — sempervivum 'black' is genuinely cold hardy. Rated RHS H5 and USDA 4-8 (hardy alpine; outdoors year-round), it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H5 means: Hardy in most of the UK and in cold winters. On the US scale that maps to USDA 4-8 (hardy alpine; outdoors year-round) — 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 −15 to −10 °C. Sempervivum 'Black' is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for sempervivum 'black' as it gets too cold:

It tolerates winter lows to about −15 to −10 °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 'black' go outside or overwinter — and where?

Plant it out within USDA 4-8 (hardy alpine; outdoors year-round) 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 'black' can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Sempervivum 'Black' hardiness — frequently asked questions

Is sempervivum 'black' cold hardy?

Yes — sempervivum 'black' is genuinely cold hardy. Rated RHS H5 and USDA 4-8 (hardy alpine; outdoors year-round), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Sempervivum 'Black' is hardy across USDA 4-8 (hardy alpine; outdoors year-round); 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 'black' can survive?

Minimum survivable temperature is roughly about −15 to −10 °C. Sempervivum 'Black' is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is sempervivum 'black'?

Sempervivum 'Black' is rated USDA 4-8 (hardy alpine; outdoors year-round) and RHS H5 — Hardy in most of the UK and in cold winters.

Can sempervivum 'black' survive winter outside?

Plant it out within USDA 4-8 (hardy alpine; outdoors year-round) 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 'black' below its minimum temperature?

It tolerates winter lows to about −15 to −10 °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.