There are other instances when walls are useful in the garden. Walls can define the garden s inner spaces, help to lead from one area to another and from one level to another. Retaining walls are probably the most common kind of walls in US gardens. Changes in grade, whether natural or contrived, help to add interest to a garden. A totally flat garden can be rather boring.
Walls don t have to be tall.
If you intend to plant the wall , it s best, if at all possible, to plant as you build. A double wall with rubble and soil in the middle will give your plants the best root run in a freestanding wall. If your wall is a retaining wall, remember to batter it back into the grade to help keep it stable. If there is sufficient moisture, ferns work quite well. I ve even had Ajuga seed itself into a wall.