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Best Soil for Raised Bed Vegetable Gardening

The Best Soil for Raised Bed Gardens

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 over 12 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!


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The Best Soil for Raised Bed Vegetable Gardening is Mel’s Mix


What is in Mel’s Mix?


Regular garden soil is too dense for raised bed gardens. Mel’s Mix for square foot gardening adds in peat moss (or coco coir) and vermiculite which keeps the soil light and airy. 

Mel Bartholomew’s mix for the the best soil for raised bed vegetable gardening is simple:

  • 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.
  • 1 part peat moss* or washed coco coir
  • 1 part vermiculite

Measure each type by volume (cubic feet), not weight. 

You can also use up to 50 percent compost to 25 percent each of vermiculite and peat moss (or coco coir)

A note about peat moss – the 3.9 cubic feet compressed bale is equal to about 8 cubic feet loose. 

Great news for Phoenix-area residents

Fall 2020  Arizona Worm Farm (located in Phoenix, Arizona) began selling “Growing in the Garden Raised Bed Mix” that is premixed and ready to go! It is available by the bag or by the yard and also available for delivery. It contains the correct mixture of compost, coco coir, vermiculite, worm castings, and basalt dust. Growing in the Garden Raised Bed Mix


What are the advantages of using this mix for raised bed vegetable gardening?

The benefits of using this soil mix for raised bed vegetable gardening include:

  • It simplifies drainage – the vermiculite and peat moss (or coco coir) 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 this mixture.Best Soil for Raised Bed Vegetable Gardening

    What’s the best way to combine the ingredients in the raised bed mix?

    One 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.

    You can also layer the ingredients (lasagne style) in the raised bed, mixing well after each addition. Best Soil for Raised Bed Vegetable Gardening


    Make up a little extra raised bed mix to use in pots and containers

    This raised bed mixture also is a perfect potting soil, so I like to mix up extra of this soil mixture 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.[line]

    Add a balanced organic fertilizer to your soil mixture for raised beds helps give plants the food they need to grow and thrive in your garden. You are feeding the soil that feeds your plants. Follow package directions for amount to add.[/left]

    Gardener's Gift Guide: Garden Favorites​


    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. 

    How to Compost: 10 Simple Steps for Composting Success


    Test your soil once a year

    About once a year after adding soil to your raised beds, it’s important to have your soil tested. A soil test can determine the health of your soil. This is the soil test kit I use. It’s  very simple to use. Gardener's Gift Guide: Garden Favorites​


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Robbie

Monday 24th of January 2022

I'm buiding a 12'x8x'22" raised garden. Should I make the whole height of the raised bed be the soil, or partially fill the bottom with sand or rocks? I'll have 65 sq. ft. of garden when I'm done or about 4-5 cu. yds. I'm not sure what to do.

Angela Judd

Monday 24th of January 2022

Hi. I wouldn't use sand or rocks, but you could absolutely use wood chips, branches, twigs, etc. to fill up to half of the height of the bed.

Maryellen Chavez

Saturday 8th of May 2021

I noticed "low desert" is mentioned. Is this mixture good in Prescott, AZ

Angela Judd

Saturday 8th of May 2021

This mixture is great anywhere.

Dana

Wednesday 24th of March 2021

My sister and I are making raised garden beds for the first time this year and we live in ok.she ordered what was supposed to be quality mix soil but instead got 2a mostly clay mix gray in color .if I add peat moss some bagged soil vermicilite will that be ok??

Angela Judd

Wednesday 24th of March 2021

Adding the vermiculite and peat moss will definitely help. I would also try to add in some high quality compost to the mixture as well.

Melissa Jimenez

Saturday 26th of September 2020

Hi! I love your posts! Would you recommend this mix for planting trees? I’m planting a desert gold peach tree and I wasn’t sure how to best prepare my clay and silt rich Tucson Az soil.

Angela Judd

Saturday 26th of September 2020

Good question. Our native soil is actually the best thing for in ground trees. It's best to plant them in the native soil rather than in an amended planting hole. This encourages the roots to branch out into surrounding soil. Best of luck to you and happy planting. I love my desert gold peach!

Marlene Fagre

Monday 24th of August 2020

I tried 50% top soil and compost, turned out badly, seeds all germinaded, only grew about 1 inch high, never higher,so if I buy pete moss and vermiculite and mix in it will change it, for the better, I'm a little bumbed and apprehensive. And the deere didn't help, some containers we put our native soil, those plants did better, just wondering if some of our dirt would help? Thank-you for your time.

Angela Judd

Monday 24th of August 2020

Are you growing in raised beds or directly in the ground? If you're directly in the ground, I would continue to add compost. If you are growing in raised beds then adding peat moss and vermiculite can help.