Cold hardiness & minimum temperature

Is Bocking 14 Comfrey (Symphytum x uplandicum 'Bocking 14')cold hardy? Hardiness zone & min temp

Also called Bocking 14 comfrey, sterile Russian comfrey.

More about bocking 14 comfrey

About Bocking 14 Comfrey

Symphytum x uplandicum 'Bocking 14' · also called Bocking 14 comfrey, sterile Russian comfrey · herb

Bocking 14 is a sterile, non-seeding strain of Russian comfrey selected at Bocking for high potassium leaf yield and reluctance to spread by seed. It is the preferred permaculture fertiliser comfrey, giving repeated leaf cuts for liquid feed and mulch. Tough and deep-rooted, it stays put rather than self-sowing, making it far easier to manage than seeding comfreys.

Cold limit: USDA 3-9 (fully hardy perennial) · RHS H7 (-1 to 30°C)

What bocking 14 comfrey's hardiness rating actually means

Yes — bocking 14 comfrey is genuinely cold hardy. Rated RHS H7 and USDA 3-9 (fully hardy perennial), it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H7 means: Hardy in the severest European continental winters. On the US scale that maps to USDA 3-9 (fully hardy 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 below about −20 °C. Bocking 14 Comfrey is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for bocking 14 comfrey as it gets too cold:

It tolerates winter lows to about −20 °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 bocking 14 comfrey go outside or overwinter — and where?

Plant it out within USDA 3-9 (fully hardy 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 bocking 14 comfrey can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Bocking 14 Comfrey hardiness — frequently asked questions

Is bocking 14 comfrey cold hardy?

Yes — bocking 14 comfrey is genuinely cold hardy. Rated RHS H7 and USDA 3-9 (fully hardy perennial), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Bocking 14 Comfrey is hardy across USDA 3-9 (fully hardy 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 bocking 14 comfrey can survive?

Minimum survivable temperature is roughly below about −20 °C. Bocking 14 Comfrey is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is bocking 14 comfrey?

Bocking 14 Comfrey is rated USDA 3-9 (fully hardy perennial) and RHS H7 — Hardy in the severest European continental winters.

Can bocking 14 comfrey survive winter outside?

Plant it out within USDA 3-9 (fully hardy 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 bocking 14 comfrey below its minimum temperature?

It tolerates winter lows to about −20 °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.