we used a systemic poison. it goes down into the roots and kills he plant from there. we cut the weeds down, but left some stem ends exposed and just dabbed some on that. we covered up the stems with a plastic bucket and let it bake in the sun. we repeated that for a number of days. it killed the weeds and nothing else. you have to very careful not to let it touch anything you want to keep. the only other reliable alternative is to buy a goat.