Answer: Thistles are perennial weeds and I'm afraid there's no product available that will kill the thistle weeds without also killing your flowers. For right now, just keep the thistles cut down to ground level and do not allow them to set flowers and seeds. In the fall you'll want to dig out your perennials, kill the thistles, remove them from the garden by digging up the dead roots, lay a weed barrier landscape fabric over the bed and then cut holes in the barrier to replant your perennials. This will keep the thistles from growing in the bed. Hope this helps!
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