I have a question about a raised garden. I'm trying to extend the garden we have now for my wife. It was a sandbox we emptied and filled with garden soil. It's doing well. The bottom of it, I noticed when emptying it, is covered over. We left it that way and the plants seem to be doing well. When extending it though, I'm curious, should I put something to cover the bottom to keep grass/weeds from growing up, or should I just tear off the grass layer and let it connect right into the ground? I'm not sure what is best and if letting the regular ground sit beneath the garden soil will cause weed/grass problems.