Thank you. Terrific article. would appreciate some further guidance -- I just bought 36" boxes of Oldham's bamboo (a clumper) and Black Bamboo (the runner you mentioned). I was going to plant the Black Bamboo in a terraced side yard as a screen and was counting on a 4 ft high retaining wall to contain the roots on my neighbor's side. Is that optimistic? Should I still put in a root barrier and, if so, how effective is it over time? Is the barrier underneath as well as on all 4 sides of the plants?