Should I let nettles grow?

My nephew, aged 10, has told me I should allow nettles in the garden for the butterflies. What butterflies and why?

He’s quite right, but nettles are troublesome weeds. They are food plants for small tortoiseshell, red admiral and peacock butterflies. If you provide nectar-rich plants such as buddleia and Verbena bonariensis, they will attract the adult butterflies.