The article I read has made me question whether or not the setup I want to use will work. I'll be planting in a pot that is about 22" in diameter, and about 8 1/2" deep. It will be placed on my deck. Because it is so shallow, it will sit close to the ground - I would like to be able to see it better, so I thought about placing the round container on top of an urn-shaped plastic container (would look very much like a birdbath). I feel I would have to place some rock in the urn container to make it more sturdy (it's about 30" high). Currently, both are empty and I tried it to see what it would look like. It's very stable - like they were made for each other. So....what do you think of this idea? Would the rock in the urn (I'd fill it about halfway) cause drainage problems for the container on top? There would be at least a 10" space between the top container and the rock in the bottom container. Any and all help would be appreciated!
BTW, it's going to be a miniature garden with different plants. I will have them grouped together based on water needs.
Sorry to be so wordy - my husband always says that I don't explain myself well enough

Thanks for your help!