I have several Snowbells planted along my concrete driveway and they have been there for years and years. This spring they seem to have spread to the other side of the driveway.....lots of them! Do they propagate by seed? And why do you think they crossed over after all these years?!!!
Certified GKH Gardening Expert
They have likely crowded their area, and have started expanding, both in roots, and by seeds. Boiling water can control these in areas that you do not want them without making your soil toxic. Just be aware that this will kill any plant that it comes into contact with, so avoid any plants that you want to keep around.