Cold hardiness & minimum temperature

Is Spartan Cliff Stonecrop (Prometheum laconicum)cold hardy? Hardiness zone & min temp

Also called Spartan Cliff Stonecrop.

More about spartan cliff stonecrop

About Spartan Cliff Stonecrop

Prometheum laconicum · also called Spartan Cliff Stonecrop · houseplant

A rare cliff-dwelling succulent endemic to the Laconia region of southern Greece, growing in vertical limestone crevices. Related to Rosularia within the Crassulaceae family, it forms tight rosettes of fleshy leaves. It shares the Sempervivum tribe's extreme cold hardiness and drought tolerance, rewarding neglect far more generously than attentive overcare.

Cold limit: USDA 6–9 · RHS H6 (-10 to 28°C)

Watch for — Crown rot in wet winters: This is a cliff endemic unaccustomed to sitting in moisture. In winter, keep nearly dry in a cool, well-ventilated spot. Use gritty soil and pots with drainage holes.

What spartan cliff stonecrop's hardiness rating actually means

Yes — spartan cliff stonecrop is genuinely cold hardy. Rated RHS H6 and USDA 6–9, 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 6–9 — 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. Spartan Cliff Stonecrop is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for spartan cliff stonecrop 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 spartan cliff stonecrop go outside or overwinter — and where?

Plant it out within USDA 6–9 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 spartan cliff stonecrop can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Spartan Cliff Stonecrop hardiness — frequently asked questions

Is spartan cliff stonecrop cold hardy?

Yes — spartan cliff stonecrop is genuinely cold hardy. Rated RHS H6 and USDA 6–9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Spartan Cliff Stonecrop is hardy across USDA 6–9; 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 spartan cliff stonecrop can survive?

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

What hardiness zone is spartan cliff stonecrop?

Spartan Cliff Stonecrop is rated USDA 6–9 and RHS H6 — Hardy throughout the UK and northern Europe.

Can spartan cliff stonecrop survive winter outside?

Plant it out within USDA 6–9 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 spartan cliff stonecrop 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.