Raised beds fail more often from the wrong mix than from the wrong lumber. Mixes that are 100% potting soil can be too light and expensive at bed scale. Mixes that are 100% native clay can bake into a brick. You want mineral bulk plus compost — with coco/peat, perlite, and a little vermiculite so the bed drains and still holds moisture. That is different from potting mix, which should stay soilless.
Backyard blend (default)
For a general vegetable bed in much of the US, this is the starting point used in the raised bed soil calculator, by volume:
- 40% screened topsoil or high-quality garden soil (mineral bulk, not bagged “fill dirt” full of rocks)
- 30% finished compost (yard waste plus manure compost is better than one tired source if you can mix)
- 10% coco peat (coir) or peat moss — use one of them, not both at full strength
- 10% coarse horticultural perlite — for air and drainage
- 10% coarse vermiculite — holds moisture between waterings
Budget blend
If you are filling a large bed and already have compost and screened soil, use more of those and smaller shares of the amendment bags:
- 50% screened topsoil or garden soil
- 35% finished compost
- 5% coco peat or peat moss
- 5% horticultural perlite
- 5% coarse vermiculite
Match the mix to the situation
| Situation | Lean toward | Watch out for |
|---|---|---|
| New bed on a patio (closed bottom) | Backyard blend (enough perlite so it drains) | Straight native soil in a sealed box stays waterlogged |
| Open-bottom bed on decent ground | Backyard or Budget; roots can go down into native soil | Still keep compost in the top 12 inches |
| Hot, dry climate | Slightly more compost and mulch on top to hold water | Very sandy mixes dry out by afternoon |
| Wet, clay native soil below | Open bottom plus Backyard blend so the fill drains | A water-tight liner turns the bed into a tub |
What to avoid
- Uncomposted manure that can burn roots and carry weed seeds
- Bagged products that are mostly shredded wood dyed brown
- Mixing in fresh wood chips throughout the root zone (they can tie up nitrogen as they decompose)
- Filling the whole frame with bagged potting mix (costly and often too light for tall crops)
- Assuming “organic” on the bag describes nutrient content. It does not replace compost quality.
After the first season
You rarely need to dump the bed and start over. Top-dress ½–1 inch of compost each year, and use the compost calculator for the volume. If plants stall, a soil test is more useful than adding random fertilizer. See how to fertilize a raised bed garden.
Frequently asked questions
Can I use only compost?
A bed of 100% compost can be too rich, too fluffy, and prone to shrinking. Blend it with mineral soil for structure — as in the Backyard or Budget recipes.
Can I use native soil from my yard?
Yes, if you screen it and mix in compost plus a little coco/peat and perlite. Heavy clay benefits from those drainage pieces. Do not use soil from an area treated with persistent herbicides. Native soil belongs in beds, not in pots.
How do I turn bed volume into bag counts?
Enter the bed size in the [raised bed soil calculator](/calculators/raised-bed-soil), pick Backyard or Budget, and read the ingredient table. It splits cubic feet (and estimated 2 cu ft bags) for each part of the recipe.