I did not know thatthere y'go, we learn something new every day
I know of using nettle juice to make curds for cheese though.....and Lady's Bestraw too, that's why cheddar is coloured, because the bedstraw roots are a good dye.
Funny enough I was just looking at a huge patch of thistles just down the road the other day. Might go back with some pruners in my pocket
cheers,
M