Gerry, maybe Owen can be your guide on how deep it should be. If 12 inches means that he has to bend over too far, you could always raise it to where he can easily reach, without being too uncomfortable. If it's a bit too deep to fill with dirt, you can always fill the bottom with other items, like large rocks, broken cement, or whatever. And, by adding boards to the sides as he grows, you can always keep it high enough for him. That means, of course, that you'll have to dig up and replant everything every few years, but sometimes, I think the extra work is worth it. This is one of those times. Owen is lucky to have a grandparent that is so caring!
