Pigs will go for the nettles, but weaners may be deterred, you could strike them with a stick to wilt them, they should then go in and remove the roots and all! With the elder, the will clear it, but as they are weaners they may have to grow a little first, we have sold pigs in the past to a couple who used them to clear Japanese Knotweed, never came back and no chemicals!