If you’re wondering what the best soil for raised bed vegetable gardening is, that’s an easy answer – “Mel’s mix”. I didn’t come up with this mix, we can thank Mel Bartholomew, the author of Square Foot Gardening, for simplifying the best soil to use for raised bed vegetable gardening.
After reading Square Foot Gardening for the first time nearly 11 years ago, I decided to start my own garden. I followed the advice for how to make Mel’s mix, which he calls “the most important, productive, essential, necessary, critical” ingredient for square foot gardening success, and it worked!
The best soil for raised bed vegetable gardening is Mel's Mix
Regular garden soil is too dense for raised bed gardens. Mel’s mix for square foot gardening adds in peat moss and vermiculite which keeps the soil light and airy.
What is in Mel's mix?
Mel Bartholomew’s mix for the the best soil for raised bed vegetable gardening is simple:
add 1 part compost – Make your own, or If you live in Arizona the compost from Arizona Worm Farm is great. If you use bagged then a mix of several different types is best.
to 1 part peat moss*
and 1 part vermiculite
Measure each type by volume (cubic feet), not weight
* A note about peat moss – the 3.9 cubic feet compressed bale is equal to about 8 cubic feet loose.
What are the advantages of using this mix for raised bed vegetable gardening?
The benefits of using Mel’s mix for raised bed vegetable gardening include:
- It simplifies drainage – the vermiculite and peat moss absorb moisture; when they are saturated, excess moisture drains away. This means you can’t overwater.
- Seeds germinate easily in the mix.
- No weeds! It really is true. In the years I’ve been gardening, I rarely see a weed inside the raised beds.
- Soil remains light and airy; it does not get crusted or compacted. Plants’ roots need oxygen as well as water, and roots love Mel’s mix.
How much soil does it take to fill a raised bed?
Determine how much soil mix is needed to fill your raised bed. It isn’t difficult, but you need to do a little math.
- Multiply the width and length of your box, and then multiply that by the number of feet deep your bed is.
- For example, if your raised bed is 4 feet long and 6 feet wide and 1 ½ feet deep, you will need a total of 36 cubic feet of the soil mix (6 x 4 x 1.5 = 36). Use 12 cubic feet each of peat moss, vermiculite, and different types of compost.
What's the best way to combine the ingredients in Mel's mix?
The easiest way to mix up the ingredients for the best soil for raised bed gardening is to combine the ingredients in batches on a tarp. Once they are combined, contents can be dumped into the raised bed. Once you fill your bed, water the soil very well.
Make up a little extra Mel's mix to use in pots and containers
Mel’s mix also is a perfect potting soil, so I like to mix up extra of Mel’s mix and store it in a large-lidded garbage can. It’s very convenient to have the mix on hand for filling pots and for other areas in the garden.
Add more compost to raised beds each time you plant
At the end of the season, as the soil level goes down from the decomposition of the compost, add additional compost to bring the soil level back up to the top of the bed. It isn’t necessary to add additional peat moss and vermiculite to your beds each season, as the peat moss and vermiculite do not break down. The continued practice of adding compost and feeding your soil each season improves the soil and the harvests.