Good soil is the single most important ingredient for a good garden. Raised beds give you an immediate advantage over a regular garden, because when you fill your raised bed, you can fill it with a blend of soil that’s superior to the native soil in your yard. Soil that’s loose and rich with nutrients and organic matter will allow the roots of your plants to grow freely, and ensure that they have access to the water and nutrients they need to sustain healthy growth.
Example: How Much Soil Do I Need for a 3×6 Bed?
To fill a 3×6 bed with 10″ sides, you will need 15 cubic feed of blended soil. To create the blend, use the following quantities:
- 9 cubic feet of topsoil (9 20-quart bags)
- 4.5 cubic feed of compost (4.5 20-quart bags)
- 1.5 cubic feet of soilless growing mix
- 1.5 cups Gardener’s Supply All-Purpose Fertilizer
- Measure your raised bed and calculate the amount of soil you need to fill it. Not so good with math? Use our Soil Calculator.
- Use The Recipe, below, to create the right blend.
If you’ll be filling more than one raised bed, you may want to buy your soil in bulk — by the cubic foot or cubic yard. We recommend these proportions:
- 60% topsoil
- 30% compost
- 10% soilless growing mix that contains peat moss, perlite and/or vermiculite, such as ProMix
Keep in mind that proportions are approximate because soil volume varies from source to source. For instance, if the Soil Calculator specifies 0.444 cubic yards of soil for your bed, go ahead and round it up to a half yard.
If you do not have access to quality topsoil, an acceptable substitute would be a 50-50 blend of soilless growing medium and compost. If you want to add peat moss to the bed, it should not be more than 20 percent of the total mix. Peat moss is naturally acidic and is not a good medium for growing vegetables.