Answer: To my knowledge there are no wood preservatives on the market that are considered safe to use on planters that hold vegetables. The obvious choice would be to use cedar or redwood lumber for the planters because they need no additional preservative treatments. Failing that, you could use Linseed oil, the classic wood treatment made from natural flax seed. Linseed oil has excellent preservative properties and water resistance. However, it is very slow drying and in cold or damp weather it may remain sticky for weeks. As a result many available linseed oils are not pure raw linseed oil but a mixture with solvents such as mineral spirits, often called ?boiled linseed oil? to speed up the drying, which makes them much less natural. So you have to be very sure you know what you are buying and remember that as a natural material, it doesn?t protect the wood from UV sunlight or mildew. Hope this information helps!
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