I was pleasantly surprised to find goutweed at the top of the list. I really like this plant and while it does spread nicely, it is not the thug for me that it apparently is for others. I love it at the foot of trees and shrubs for easy maintenance and a splash of brightness. Houttuynia is a stinky plant for me, I don't care for it. I haven't actively tried to eradicate it (mainly because I hate to pull it up, I can't abide the smell), but it has not spread beyond the one corner I planted it in. It does well as a marginal plant for those who might want to contain it by simply dropping a pot into your pond.