Cold hardiness & minimum temperature

Is Broad-Petalled Cranesbill (Geranium platypetalum)cold hardy? Hardiness zone & min temp

Also called Broad-Petalled Cranesbill, Broad-Petalled Geranium, Hardy Cranesbill.

More about broad-petalled cranesbill

About Broad-Petalled Cranesbill

Geranium platypetalum · also called Broad-Petalled Cranesbill, Broad-Petalled Geranium · flowering

Geranium platypetalum is a robust herbaceous perennial native to the Caucasus region and northern Iran, forming dense mounds of large, deeply lobed, softly hairy leaves. It thrives in moderately fertile, well-drained soil in full sun to partial shade and is prized for its violet-blue flowers with darker veining produced in early to mid-summer. The single most important care task is cutting back hard after flowering to encourage a flush of fresh foliage. According to ASPCA guidance, true Geranium species (cranesbills) are non-toxic to cats and dogs.

Cold limit: USDA 5-8 · RHS H6 (-20 to 25°C)

Watch for — Vine weevil: C-shaped grubs feed on roots in late summer to autumn, causing plants to wilt and collapse; treat container-grown plants with nematodes (Steinernema kraussei) from August to October when soil temperature is above 5°C.

What broad-petalled cranesbill's hardiness rating actually means

Yes — broad-petalled cranesbill is genuinely cold hardy. Rated RHS H6 and USDA 5-8, 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 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 −20 to −15 °C. Broad-Petalled Cranesbill is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for broad-petalled cranesbill 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 broad-petalled cranesbill 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 broad-petalled cranesbill can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Broad-Petalled Cranesbill hardiness — frequently asked questions

Is broad-petalled cranesbill cold hardy?

Yes — broad-petalled cranesbill is genuinely cold hardy. Rated RHS H6 and USDA 5-8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Broad-Petalled Cranesbill 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 broad-petalled cranesbill can survive?

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

What hardiness zone is broad-petalled cranesbill?

Broad-Petalled Cranesbill is rated USDA 5-8 and RHS H6 — Hardy throughout the UK and northern Europe.

Can broad-petalled cranesbill 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 broad-petalled cranesbill 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.