Answer: It's important to at least break up the soil surface before you construct and fill your raised beds so you don't leave an impenetrable layer between the original soil and your raised bed. Digging down 6-8 inches and incorporating some of the new soil and amendments would result in good water drainage, and root penetration. Finished bed soil depth will depend upon what you plan to grow. 10-12 inches of soil depth is minimum for annual plants and 18-24 inches will work for most herbaceous perennials.
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