As I mentioned in another post, I am fairly restricted when it comes to planting veggies as I can not plant them in the ground where I live. I am looking into all kinds of options, including home-made "Earth Boxes". I had originally built my wife an 18" wide, 8' long, 18" deep planter box so she can plant veggies. After building it and filling it, we learned that this box was heavy. Actually to call it heavy might be a little misleading. I believe the technical term is: Really, really, really heavy. So the idea of moving the box to change lighting conditions to suit different plants was out the window. Recently, while I have been looking into other options, I have split up this long box into smaller ones that will be more manageable by the two of us and can be moved around. I may even put large casters on it so that it can be rolled.

My question is: How deep should I keep these boxes to suit most vegetables? 18" seemed like over-kill for her carrots and her snap peas didn't utilize the full depth either. About the only plants that did use up the full 18" of dirt were my sweet potatoes and her raspberry bush, which sent out runners and took over its side of the box and was starting to move into the other side. Should I stick with 18" depth or could I get away with reducing this to 12" or maybe even less?

Thanks again!