Cinquefoil

Cinquefoil - potentilla species. Does anyone know of a good use for these? We straw mulched an area of grass and these blinkin' things are popping up all over the place through the straw and are becoming 'choke cover' not ground cover. And oh boy, do they spread at an alarming rate!!! I am doing my best to pull them out but the top inevitably breaks from the root so I guess that means further outbreaks. Any ideas how to get rid of them permanently? Are they useful for anything and then at least I could appreciate them more?