If you move them with the intent of leaving them to their own devices then there would be no problem....your leaving them to their own devices. If you "leave them to their own devices" then I am assuming you mean you are planting them somewhere out on their own. If you do this in a flower bed with other plants then yes you will have to keep up with them. Remember, no plant is the dominate species at all times...succession eventually wins out. I guess I am a loosestrife fan.
