QuestionsHow to growTrees and ShrubsWeedsnettles 0 Vote Up Vote Down noel mc namara asked 16 years ago what can iget to kill off nettles and will it kill them off for good 1 Answers 0 Vote Up Vote Down Gerry Daly Staff answered 6 years ago Roundup applied as directed on the pack will kill nettles, or cover the whole area with old carpet or black plastic until growth is finished.