By Azura · Updated June 2026 · Raised Garden Hub is reader-supported. When you buy through links on our site, we may earn an affiliate commission at no extra cost to you.
The dirty secret of raised bed gardening: the soil costs more than the bed. A single 4×8 bed at 18 inches deep needs about 48 cubic feet of fill (a more common 12-inch-deep 4×8 bed needs about 32). Buying that all as bagged mix gets expensive fast. Here’s how to do it for much less.
Rule of thumb: Only the top 8–12 inches needs premium soil. Everything below that can be cheaper organic filler that breaks down over time.
Method 1: Hugelkultur (best for deep beds)
Layer the bottom third with logs, branches, and woody debris, then add leaves, grass clippings, and compost, and finish with quality soil mix on top. As the wood breaks down it holds water and feeds your plants for years.
Method 2: Lasagna layering
Alternate “browns” (cardboard, dry leaves, straw) and “greens” (kitchen scraps, grass, manure), then cap with soil mix. Great for shallower beds and for using up yard waste.
What to put on top
The top layer is what your roots live in for the first season, so don’t cheap out here. A proven mix is roughly:
- 50% compost or quality topsoil
- 30% organic matter (aged manure, leaf mold)
- 20% aeration (perlite or coarse sand)
Don’t fill it with these
- Fresh wood chips on top (they steal nitrogen from your plants)
- Pure garden soil (compacts and drains poorly in beds)
- Anything treated with herbicides
Ready to pick the bed itself? See our best raised garden beds of 2026.