How to Prune blue comfrey?
Generally not required but old or fading foliage can be trimmed

blue comfrey · Symphytum × uplandicum
Also known as: Russian comfrey
Grow in moderately fertile, moist soil in sun or partial shade. Be aware the plant growth can be vigorous once established and has the potential to become a nuisance, so will require appropriate management. Can be grown for use as a plant fertiliser
Generally not required but old or fading foliage can be trimmed