valleylynn said: Wow! Urban, you make me want to get outside and plant up some containers. Those are awesome!
Using top dressing will help keep them healthy on the undersides. I would definitely top dress. The roots will grow down through the gravel.
Here is one I did a couple of years ago.
It is not as colorful as yours. I think I have some colorful containers in the shed. Going to check and see.