Comfrey is the gardener's best friend. It can be used as a nutrient-rich mulch, a beautiful pollinator attractor, and a “compost booster”, as its leaves are full of nitrogen, phosphorus and potassium. 
Comfrey is too vigorous to grow in a pot, so it will need plenty of space in the garden (it can leave up to 20 years!), a good soil and abundance of sunlight.
Once settled it needs little maintenance, however extra feeding with manure and compost will encourage leaves production.