To fill a raised garden bed, you only need quality soil in the top 12 inches — a blend of one-half to two-thirds topsoil with one-third to one-half compost, per the University of Minnesota Extension. Anything deeper than 12 inches can be coarse organic material: logs, branches, leaves. That two-layer approach fills a deep bed…

How deep should a raised garden bed be? Most need 10–12 inches of soil — but only if the bed sits on a hard surface like a patio, driveway, or gravel. If your bed sits on open ground, roots grow straight down into the soil beneath it, and 6–8 inches deep is often plenty. The…