Thanks so much, everyone.
When I want to obscure the outer wall, I first remove it all, along with the gates. The I place the outside wall, being sure it is facing the outside. Then I sink the fence all the way around far enough that you can't see the edge on level ground. Then it is just a matter of adding the right foliage, some on the inside and some on the outside, depends on the look I want. Sometimes I also sink the foliage so that it is very bushy. The in-game dogwood looks great with 4 trees to a square and then sunk down 2 or 3 levels. Then you can add a decorative fence along the edge of the foliage for a finished look, but sometimes, I just leave the foliage to serve as the wall. It can be a slow process. I put it in, take it out, try something else......slow poke.