I know some members will think this a real dumb question, but I'm going to ask anyway! :? I want to put a "path" of some sort through my gravel layout. Will the sand and gravel eventually mix? If so, I have an idea to install a barrier between the gravel and sand. The barrier is made of thick plastice strip with gravel attached along the top and half way down the sides using sealant. Then plant Heminathus cuba in the gravel along the edge; but will a solid barrier have any effect on water circulation through the substrate? (Still trying to work out how to post a photo!).