Mine is spreading but not too quickly. It's been in the ground for about 5 years, and there are a lot of shoots coming up this year for the first time. It looks like I'm going to have to do some root-pruning. The ground it is in is very heavy clay so it might spread worse if it is in good soil. I don't know how badly it spreads by seed since I dead-head as soon as the blooms fade.

I collect seed to share with others so I rarely, if ever, dead head anything. I've had elecampane volunteers pop up occasionally in the lawn. Maybe a couple a season. But it is nothing can't be mowed over or dug up. Elecampane has a single long root. It does not spread by stolons (like mint) and so is pretty controllable.

Elecampane has a pretty typical "perennial spread," as I call it. Like other perennials it will grow into a larger, more robust clump as the years progress. Be sure to give it space. My elecampane is 6+ feet tall with its largest leaves over 2 feet long. The flowers are very sunny and cheery.

FataMorgana