Mel's Mix (1:1:1 compost, vermiculite, peat moss/coir)

Mel's Mix, from Mel Bartholomew's Square Foot Gardening method, is the most widely recommended raised bed soil recipe: equal parts (by volume) blended compost, coarse vermiculite, and peat moss (or coconut coir as a sustainable substitute). This creates an exceptionally light, well-draining medium that retains moisture without waterlogging. Seeds germinate quickly in the loose, airy texture. The critical success factor is compost quality: use compost from at least 3-5 different sources (mushroom compost, worm castings, composted manure, leaf mold) for diverse nutrient profiles. Coarse or super-coarse vermiculite provides aeration and moisture retention; fine-grade vermiculite compacts too much. Expect to pay $150-300+ to fill a 4x8x12-inch bed depending on sourcing. Criticism: at roughly 33% compost by volume, Mel's Mix contains far more organic matter than natural soil (about 10%), which some soil scientists consider excessive. The mix settles significantly as organic matter decomposes, requiring annual top-ups.