You can use marine treated plywood.It's treated with a fungicide and very versitle as far as the way you construct the stand.If you are using round pots,then cut round holes in 8 inch wide by 4 ft long strips and lay them across your rack setting the pots in the holes.If square then cut square.Just make sure you put something in the center for support if you don't use the 3/4 plywood.Hope it was a helpful hint!

Ga Grown!