Answer: The nice thing about raised beds is that you can customize the planting media. I use a 3-way topsoil in mine. It is essentially an equal mixture of garden soil, builder's sand and compost. Since you already have the garden soil/fill dirt in the bed, plan on adding some builder's sand (to help your clay soil drain well) and an equal volume of compost or other organic matter (to help hold moisture, keep the soil loose, and add nutrients to the roots of your plants. You can start by spreading 3-4 inches of organic matter over the top of the bed and digging it into the soil. After planting add another 2-3 inches over the top of the soil with the intention of digging it into the soil at the end of the growing season and adding fresh organic matter. This will help suppress weeds and slow evaporation and will also enrich the soil when you dig it in at the end of the season. A few years of this practice and you will have rich garden loam in your raised bed.
Enjoy your garden!
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