There is no denying raised garden beds provide many benefits. The beds make gardening easier by reducing the distance the gardener has to bend down. The soil allows the gardener to plant sooner and because raised beds need to have soil added to them, they can solve virtually any soil problem - too much clay, too much sand, poor drainage, etc.
One question many avid gardeners have with raised beds is what type of soil is the best to fill the new garden. If you are building raised beds, you will need a mixture of materials to provide a soil mix with good fertility, good drainage, and good moisture holding abilities along with a suitable pH.
If decent garden soil is accessible, you can certainly use that. But most gardeners find they need to bring in additional soil when building a raised planting bed or planter because of the large amount needed to fill a bed. Importing top soil to fill the raised bed can have mixed results. Top soil is not a regulated material, so all kinds of soil can be sold as top soil. A reputable supplier should be able to give you soil test results and provide samples to reassure you about the quality of their product. A good local nursery or your county extension should be able to recommend a source.
Besides using imported top soil, a homemade mixture can also be made for the raised beds. The rule of thumb for mixing your own garden soil is to use one-third compost, one-third moisture retaining materials such as coconut coir or peat moss, and one-third drainage material such as sand, vermiculite, or perlite. This method may be a bit more pricey, but the soil mixture is rich, virtually weed free, and friable.
Any soil in a raised bed will settle over time, so plan on regular additions of organic matter to maintain soil depth in the bed. Using organic mulch year round will also help feed and replenish the soil on an ongoing basis. Another option is to cover and protect the soil surface by growing a cover crop every winter, then turn that under each spring as a source of organic matter.
Anne Lenox Barlow has had experience in the agricultural field as a horticulture educator with Cornell Cooperative Extension in Clinton County. She can be reached by e-mail at firstname.lastname@example.org.