Cold hardiness & minimum temperature

Is Houseleek Saxifrage (Saxifraga sempervivum)cold hardy? Hardiness zone & min temp

Also called Houseleek saxifrage, Porophyllum saxifrage.

More about houseleek saxifrage

About Houseleek Saxifrage

Saxifraga sempervivum · also called Houseleek saxifrage, Porophyllum saxifrage · flowering

Saxifraga sempervivum is a Porophyllum (Engleria) section alpine perennial native to rocky limestone habitats in the Balkans and northern Greece, where its tight, silver-grey rosettes superficially resemble a Sempervivum — hence the common name. It produces wiry, reddish-purple, glandular flower stems bearing small pink-purple flowers from late winter into spring. Like other Engleria saxifrages, it demands sharp drainage, alkaline soil, and a cool root run, and is most successfully grown in an alpine house or trough. The genus Saxifraga is not listed as toxic to cats or dogs by the ASPCA.

Cold limit: USDA 4-7 · RHS H5 (-18°C to 20°C)

Watch for — Botrytis in compact rosettes: Grey mould (Botrytis cinerea) can develop unseen in the tight leaf clusters, particularly over winter; ensure maximum ventilation, water only at the base, and remove any dead leaves promptly.

What houseleek saxifrage's hardiness rating actually means

Yes — houseleek saxifrage is genuinely cold hardy. Rated RHS H5 and USDA 4-7, 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 4-7 — 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. Houseleek Saxifrage is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for houseleek saxifrage 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 houseleek saxifrage go outside or overwinter — and where?

Plant it out within USDA 4-7 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 houseleek saxifrage can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Houseleek Saxifrage hardiness — frequently asked questions

Is houseleek saxifrage cold hardy?

Yes — houseleek saxifrage is genuinely cold hardy. Rated RHS H5 and USDA 4-7, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Houseleek Saxifrage is hardy across USDA 4-7; 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 houseleek saxifrage can survive?

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

What hardiness zone is houseleek saxifrage?

Houseleek Saxifrage is rated USDA 4-7 and RHS H5 — Hardy in most of the UK and in cold winters.

Can houseleek saxifrage survive winter outside?

Plant it out within USDA 4-7 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 houseleek saxifrage 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.