I have a stone retaining wall we just finished. We want to have something green to crawl it, not just for looks, but to help strengthen the wall as well. At the bottom of the wall is our lawn, and on top of the wall we have 2 quakey aspens. So I want something that will not grow into my lawn, and will not choke my trees. Something that will not grow beyond our control. You know...we want to be able to choose where it decides to grow. Basically I dont want to be posting here in a year that I can't get rid of something that we should not have planted. Any help will be greatly appreciated. I have called 4 nurseries and they all contradict each other so far. Thanks so much!