Is it wise--or completely insane--to build a raise bed directly over my cemented area in the backyard? It's a corner in my backyard cornered by two fences. The bed is 60 inches wide and 16 inches deep surrounded by a strong wall of square bricks. And the dirt wouldn't really be touching the fences to avoid water-rotting them. But my concerns are:
Drainage) Will the water be able to drain successfully?? Where will the water drain to if it's only 16 inches of dirt sitting directly on cement? Should I first put a giant sturdy piece of wood at the bottom of the bed with irrigation holes in it with a number of bricks under it to leave space between the cement and the bed for drainage?
What to plant?) Should I only plant things that are known for having shallow roots since the dirt is only 16 inches deep (and what would those plants be?)? Should I only plant bulbs as they generally don't root too deep?
Here's a quick before-and-after drawing I did on the computer to illustrate what I'm considering building. As you can see, there's already plants growing on that un-cemented strip of dirt in front of the fences.
Thanks very, very much in advance. Thus far this forum has provided me with priceless knowledge.