That would not be my first choice of campanulas for a groundcover. It is a clumper, not a spreader, so you would need to plant quite a number to get the coverage and density you may want or need. One of the Serbian or Dalmation species would be better - C. portenschlagiana or poscharskyana. These spread nicely; when well established, do keep weeds down and have long midsummer bloom period and can be cut back to tidy up, refresh foliage and keep size in check. You can also encourage a light, repeat bloom by cutting back after the initial bloom cycle.

Thank you. I'll investigate the varieties you suggested.

Campanula poscharskyana does a beautiful job for me and reseeds nicely. I grow mine under my roses.