How do I save seeds from my bellflower superba plant

Question

The plants are in a bed of rocks and I need to move them. I do not know if they are seeded from year to year or if they are rhizomes

Answer 1

As summer ends pollinated flowers develop seeds or seed capsules. Most members of the bellflower family develop small, hard capsules filled with tiny black or brown seeds. By snipping off the seed capsules and dropping them into a paper bag, you may scatter the seeds in other parts of the garden immediately or save them for spring planting.
https://www.gardeningknowhow.com/ornamental/flowers/campanula/growing-campanula-bellflowers.htm