Cold hardiness & minimum temperature

Is Delphinium 'Galahad' (Delphinium elatum 'Galahad')cold hardy? Hardiness zone & min temp

Also called Galahad delphinium.

More about delphinium 'galahad'

About Delphinium 'Galahad'

Delphinium elatum 'Galahad' · also called Galahad delphinium · flowering

'Galahad' is a Pacific Giant (Round Table) Delphinium elatum hybrid bearing tall, elegant spires of pure white, fully double flowers with white bees in early summer. A classic back-of-border perennial reaching 1.5-1.8 m, it demands full sun, rich moist soil, shelter and firm staking. Like all delphiniums, it is toxic to cats and dogs.

Cold limit: USDA 3-7 · RHS H6 (-34 to 24°C)

Watch for — Crown rot: Soggy, poorly drained soil rots the crown over winter. Improve drainage, keep mulch off the crown, and avoid waterlogged sites.

What delphinium 'galahad''s hardiness rating actually means

Yes — delphinium 'galahad' is genuinely cold hardy. Rated RHS H6 and USDA 3-7, 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 3-7 — 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 −20 to −15 °C. Delphinium 'Galahad' is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for delphinium 'galahad' 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 delphinium 'galahad' go outside or overwinter — and where?

Plant it out within USDA 3-7 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 delphinium 'galahad' can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Delphinium 'Galahad' hardiness — frequently asked questions

Is delphinium 'galahad' cold hardy?

Yes — delphinium 'galahad' is genuinely cold hardy. Rated RHS H6 and USDA 3-7, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Delphinium 'Galahad' is hardy across USDA 3-7; 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 delphinium 'galahad' can survive?

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

What hardiness zone is delphinium 'galahad'?

Delphinium 'Galahad' is rated USDA 3-7 and RHS H6 — Hardy throughout the UK and northern Europe.

Can delphinium 'galahad' survive winter outside?

Plant it out within USDA 3-7 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 delphinium 'galahad' 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.