Cold hardiness & minimum temperature

Is Geranium nodosum (Geranium nodosum)cold hardy? Hardiness zone & min temp

Also called Knotted cranesbill, Knotted geranium.

More about geranium nodosum

About Geranium nodosum

Geranium nodosum · also called Knotted cranesbill, Knotted geranium · flowering

Knotted cranesbill is a tough, shade-loving European woodland perennial with glossy, three-to-five-lobed leaves and long-lasting funnel-shaped flowers in pink to lilac-purple, often faintly veined, from late spring well into autumn. One of the best hardy geraniums for dry shade, it spreads gently, copes under trees and dies back in winter.

Cold limit: USDA 4-8 (outdoor perennial) · RHS H6 (-23 to 24°C)

What geranium nodosum's hardiness rating actually means

Yes — geranium nodosum is genuinely cold hardy. Rated RHS H6 and USDA 4-8 (outdoor perennial), 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 4-8 (outdoor perennial) — 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. Geranium nodosum is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for geranium nodosum 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 geranium nodosum go outside or overwinter — and where?

Plant it out within USDA 4-8 (outdoor perennial) 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 nodosum can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Geranium nodosum hardiness — frequently asked questions

Is geranium nodosum cold hardy?

Yes — geranium nodosum is genuinely cold hardy. Rated RHS H6 and USDA 4-8 (outdoor perennial), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Geranium nodosum is hardy across USDA 4-8 (outdoor perennial); 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 nodosum can survive?

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

What hardiness zone is geranium nodosum?

Geranium nodosum is rated USDA 4-8 (outdoor perennial) and RHS H6 — Hardy throughout the UK and northern Europe.

Can geranium nodosum survive winter outside?

Plant it out within USDA 4-8 (outdoor perennial) 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 nodosum 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.