Just Say No to Abuse Declaring War on Terrorism. Most plants that set viable seed will seed around a bit if they are happy.
Some plants can cover a fair amount of ground via self-sown seed.
A couple of my favorite groundcovers and a couple of lovely thugs. There pace is more of a steady trot. These are all very easy to control if they put themselves where you don t want them. Better manners, but steadily increasing cover without any effort on your part. The first year it sleeps, the next year it creeps and then it leaps.