plant
Comfrey
A gardener's plant more than a kitchen one: unmatched as a fertiliser, no longer used internally.
Growing
Almost impossible to kill. Choose a sterile cultivar such as Bocking 14 unless you want it to seed everywhere.
Liquid feed
Pack leaves into a container, weigh down, collect the black liquid after three to four weeks and dilute 1:15. High in potassium — good for fruiting crops.
In the compost heap
A superb activator. Chop and layer with brown material.