Ive got a customer that wants flower bed boxes installed in front of her house. She wants to use large landscape timbers. Should I use the pressure treated timbers at a homedepot (largest they have is 5 1/2x 5 1/2) or is there something else I should look into. 2nd question What is the proper way to install the larger landscape timbers? Should I bury the first layer like I would when doing a stone wall? Do I bury a 4x4 post into the ground so I can attach the timbers to that (so the wall doesnt cave in or out)? If so, do I use cement or just back fill with dirt and pack it good? If I do use post, how far up should the post be exposed?, flush with the top of the wall or should it end 1 layer short of the top so that its covered with dirt and mulch?