Some plants just dont play well together. Unfortunately they produce lots of seeds as well as being perennials. Options would be to continue to weed and do not let them reseed. Eventually you will wear them out. 2) Could use a non selective herbicide such as Round up but it must be kept off plants you want to keep and will do nothing to control seeds until they germinate. 3) black palstic over the area all summer will help to kill off the seeds and plants but you give up your garden for the season. 4) you could mulch with several layers of newspaper covered with 3-4 inches of wood mulch aroudn the exisitng good plants. 5) not real practical to remove soil. you would have to remove the top 6-8 iinches of soil to be sure you got the seeds. good luck, sandy
