Hi, I can tell you a few things. It will make lots of seeds that are easy to collect. The plant will develop seed pods that will dry and small openings will start to appear on the tops of the pods when the seed is ripe. I know the seeds will winter sow well. I don't know if you can spring sow as well. The plants are very winter hardy. They grow to a couple of feet making sturdy non-flopping stalks of large flowers. They are not rampant spreaders like bellflowers. If the plant is drought stressed in late summer, it may go dormant, so part shade is best. Hope that helps some, Remy

Gardening is really a fascinating (& frustrating) experience. I could not even get 3 plants of campanula persificolia to overwinter in an amended clay bed near my house (upper part of the yard with the best drainage). Certainly can't imagine it being invasive. LOL. I also can't imagine nice loose soil that looks like yours Eigdeh :~) Great job! Don't you know soil is this dense sticky stuff you cut out with a sharp spade in spring or take a pick-axe to in summer! C. glomerata, which is invasive for many, can survive and even spread a bit in a ground level bed in my yard and I did manage after several tries to get milky bellflower going in a highly amended somewhat raised bed.

this is a double post. best to respond in the other thread.

Thanks very much, all of you. I appreciate the advice about digging wide and deep, and not just yanking the roots as it's clear from what you've said I will only get replication of the plant. It sounds like it's going to be quite a job because it is next to a dry-laid stone retaining wall. I will be sure to bag every scrap of plant material and dispose of it in the trash. I have already enough invasive thug plants -- lady bells (adenophera), Cyprus spurge, self-heal, and a neighbor's Japanese knotweed.