Put the comfrey leaves and stalks in a water butt and soak for a few months. The resulting liquid is a terrific veg fertiliser. They're ok composted too, though it's a pity to do that when you can instead have a supply of liquid veg booster available all summer. Another good thing to do with the leaves is to chop them up and add them generously to last year's potting compost. As good as new.

My comfrey patch is well-behaved. The plants stay put where I planted them. They're far more likely to be swamped by stinging nettles than they are to go all native on me. The variety to go for is Bocking 14. It's pretty well-behaved.