Cold hardiness & minimum temperature

Is Geranium cinereum var. subcaulescens (Geranium cinereum var. subcaulescens)cold hardy? Hardiness zone & min temp

Also called Subcaulescent cranesbill, Vivid magenta cranesbill.

More about geranium cinereum var. subcaulescens

About Geranium cinereum var. subcaulescens

Geranium cinereum var. subcaulescens · also called Subcaulescent cranesbill, Vivid magenta cranesbill · flowering

Geranium cinereum var. subcaulescens is a low alpine cranesbill prized for intense, vivid magenta-crimson flowers with a striking near-black centre, carried over grey-green rosettes through summer. Sun-loving and compact, it brings electric colour to rock gardens, troughs, gravel and sharply drained border fronts, flowering longest where drainage is excellent.

Cold limit: USDA 5-8 · RHS H5 (-15 to 24°C)

Watch for — Crown and root rot: Its main weakness, driven by wet or heavy soil and winter damp. Plant in sharp drainage, grit around the crown, and avoid covering the rosette with mulch.

What geranium cinereum var. subcaulescens's hardiness rating actually means

Yes — geranium cinereum var. subcaulescens is genuinely cold hardy. Rated RHS H5 and USDA 5-8, 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 5-8 — 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 about −15 to −10 °C. Geranium cinereum var. subcaulescens is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for geranium cinereum var. subcaulescens 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 geranium cinereum var. subcaulescens go outside or overwinter — and where?

Plant it out within USDA 5-8 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 geranium cinereum var. subcaulescens can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Geranium cinereum var. subcaulescens hardiness — frequently asked questions

Is geranium cinereum var. subcaulescens cold hardy?

Yes — geranium cinereum var. subcaulescens is genuinely cold hardy. Rated RHS H5 and USDA 5-8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Geranium cinereum var. subcaulescens is hardy across USDA 5-8; 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 geranium cinereum var. subcaulescens can survive?

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

What hardiness zone is geranium cinereum var. subcaulescens?

Geranium cinereum var. subcaulescens is rated USDA 5-8 and RHS H5 — Hardy in most of the UK and in cold winters.

Can geranium cinereum var. subcaulescens survive winter outside?

Plant it out within USDA 5-8 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 geranium cinereum var. subcaulescens 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.