We used deck stain on the outside only. The inside was lined with landscaping fabric before putting in the soil and herbs/vegetables. Since this is cedar it will naturally do well outside, but my friend didn't want it to grey. They originally wanted me to build this out of pine, but I refused. The cost wasn't that much more, and this will be around for a very long time.
Okay, thanks for the reply. I think I'll follow what you did, just protect the outside of the wood and lay down some fabric on the inside. I have some extra redwood lying around and this looks like a perfect project!
Txhome, I didn't really draw up any plans for this. I can tell you that I glued and pocket holed the side panels and the legs together because I didn't want any fasteners to show. The bottom shelf is even pocket holed from underneath. It's held up incredible well over the years.