Answer: If you have problems with gophers or moles, setting mesh screen in the bottom of your raised beds would be a good idea. That will keep them from tunneling up and into your beds. If you do not have a problem with them, you can skip the mesh. I would not put a board at the bottom between the native soil and the topsoil you add to your raised bed. This artificial barrier will stop the natural percolation of water through the soil and will end up producing a layer of soggy, rotting wood at the bottom of the bed. If you do not need to put mesh down to keep gophers and moles out, simply scuff up the native soil and then add your topsoil. This will allowe perfect drainage for your plants.
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