I purchased a home recently and it has a 15' x 15' above ground sandbox which is sturdily constructed of treated lumber. Its in the sunny spot of my yard of course - right where I'd like to put a veggie garden. I've been trying to give it away for free on various ad sites with no luck. If I were to remove a hefty portion of the sand and add soil, how much depth of soil would you recommend? And is the treated lumber any concern? Should I put a liner in it if I go this route? Thanks,
Converting a Sandbox
Certified GKH Gardening Expert
Yes, a liner is recommended when treated lumber will be used in a raised bed vegetable garden. Without a liner the wood could potentially leach toxins into your garden.
At least 6-8 inches of garden soil are required for a raised bed, but 12 inches or more is ideal. You can mix in a portion of the sand you already have (up to about 60%) as desired with the new soil, depending on the final soil texture you want to build.
This article provides more advice on raised bed gardening: