Nice setup Brain. I like your idea of sand gravel mulch; easy to manage with your intentions in mind. Sand, if coarse enough, would make for very uniform watering as well. Another nice feature it that its pretty much an inert media. Sand can be a very good insulator when thought of as a poor conductor of heat. But it also retains heat (like passive solar) so you have to watch for a cumulative temperature build up over a period of time. I'd try it. I'm really interested in what the temperature differentials would be, air vs. pot using your set up and idea.
As a side note, We have a certain type of striped gopher( the tan and brown striped about twice the size of a chipmonk-- not the pocket gopher type that leave a mound of dirt above ground) and in the last 20 years or so I have had a gopher problem maybe five or six times-- so there are skips of two or three years experienced. The interesting thing is when I get one, It digs a hole in the exact same spot as the previous gopher--even where there's a skip of years. I am puzzled by this. It's so predictable that five years ago I put an (iron rod) trap anchor there permantly.
