Hi Judy,

I've had some success with digging out as much as I can and THEN smothering it under wood mulch. But there's no harm in trying this.

These two pages have good information:

https://extension.umn.edu/weeds/creeping-bellflower

https://northerngardener.org/creeping-bellflower/

This page mentions smothering it:

https://hennepinmastergardeners.org/invasion-of-the-creeping-bellflower/

If you’re going to dig, don’t be fooled into thinking you have the whole plant when you dig up two or three inches of hairy white roots. Those upper roots are often linked to big carrot-like roots that can be 12 to 18 inches below ground.

Plants are most susceptible to herbicide when they first emerge in spring, when they flower and in fall when plants are starting to go dormant. Sometimes multiple applications of the chemicals are needed to kill the plants.

Don’t let the plants go to seed after flowering. Good luck.