I have a stockade fence around my back yard, and on one side my neighbor has allowed trees and shrubs to grow up right along the property line. As a result, I get the branches hanging over - to the sun side - and roots in my back lawn and gardens. I'm digging a small trench (4-6 in.) along the fence to cut the surface roots, I'd also like to go deeper with some kind of barrier. Something bigger than lawn edger - I'm thinking more like 6-10 in. to stop the roots, or at least seriously slow them down. Is there a barrier product that I could use to run 30-40 ft along the fence?