Cold hardiness & minimum temperature

Is White Comfrey (Symphytum orientale)cold hardy? Hardiness zone & min temp

Also called White Comfrey, Eastern Comfrey.

More about white comfrey

About White Comfrey

Symphytum orientale · also called White Comfrey, Eastern Comfrey · flowering

White Comfrey is a shade-loving perennial native to Turkey and the eastern Mediterranean, producing loose clusters of pure white tubular flowers in mid-spring before most border plants emerge. Less spreading than common comfrey, it suits the woodland edge and shaded border. The soft, hairy foliage dies back after flowering, leaving space for summer companions.

Cold limit: USDA 5–9 · RHS H6 (-15 to 22°C)

What white comfrey's hardiness rating actually means

Yes — white comfrey is genuinely cold hardy. Rated RHS H6 and USDA 5–9, 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 5–9 — 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. White Comfrey is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for white comfrey 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 white comfrey go outside or overwinter — and where?

Plant it out within USDA 5–9 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 white comfrey can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

White Comfrey hardiness — frequently asked questions

Is white comfrey cold hardy?

Yes — white comfrey is genuinely cold hardy. Rated RHS H6 and USDA 5–9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. White Comfrey is hardy across USDA 5–9; 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 white comfrey can survive?

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

What hardiness zone is white comfrey?

White Comfrey is rated USDA 5–9 and RHS H6 — Hardy throughout the UK and northern Europe.

Can white comfrey survive winter outside?

Plant it out within USDA 5–9 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 white comfrey 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.