Dig them up With the rhizomes attached ( bear in mind that like other pernicious plants every broken piece of root can reroot readily) and then as plantlets appear hoe them down.This you will have to keep doing until they don't reappear.
In this period of self-help you may be interested to know that nettles provide; soup,tea and clothing if you are so inclined and a home for butterflies. At home we grow them to make soups and teas and we have the leaves as green veg, along with the dandelions and no I don't go around hugging trees nor wear socks with my sandals!!