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!
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 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.
Good news for Phoenix-area residents
Beginning fall 2020, Arizona Worm Farm (located in Phoenix, Arizona) is selling a “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.
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 (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 Mel’s Mix.
What's the best way to combine the ingredients in Mel's 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.
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 organic fertilizer to your soil mix before planting
Adding 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. This is the recipe I use to make organic fertilizer when I add new soil to raised beds.
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.
About 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.
What do you want to read next?
It really is a great way to begin gardening. Raised bed gardening simplifies so many things. I’ll check it out, thanks for commenting!
Angela~
What would you recommend for installing lots of garden at once? Like ordering by cubic yards instead of bags. Any vendors you recommend in Phoenix?
Arizona Worm Farm will deliver compost. You can also pick up small and large amounts on site.
I am buying the ingredients to make mel’s mix for some raised beds- but I am finding it quite expensive! I need ~30 cubic feet of mix but am finding only 8 or 10 qt bags of peat moss and vermiciulite on Amazon for about $13 each- so added up that’s quite a bit. Any advice for this or where to buy? Am i miscalculating this? LOL
I am getting compost from AZ Worm farm tomorrow for a fair price -it’s the other two i’m finding to be pricy!
PS I’m glad to have discovered your site! I followed you on Instagram and stalk your site regularly as well- love your tips!
Maybe it’s my math that’s wrong- i need 48 cu ft of the mix (8x4x1.5)
The best price I found for peat moss is $10 for a large bale (the 3.9 cubic feet compressed bale is equal to about 8 cubic feet loose) is at Home Depot. The best price I’ve seen is the 4 cubic foot bag of vermiculite on Amazon. II found when filling my most recent beds I used about 40% compost and then 25% vermiculite and 35% peat moss.
Thank you! I’ll check Home Depot!
Not new to gardening, just new to this process. I have raised garden beds. There is already soil in them. Can I mix this with the soil already in the beds or start over.
Thank you!
It depends on what the condition of the soil in the bed is. More than likely you can add this to the top of your beds to fill them back up and that would be fine. If the soil is very compacted poor you may want to consider replacing all or part of it. If you have more than one bed, consider starting with just one to see how it does. Aim for a depth of 6-8 inches of new soil.
My father and I are interested in building sub irrigated raised garden beds. Would this mix work well with this kind of garden bed? Thanks in advance!
Yes! This soil mix absorbs moisture well and is light and friable. Best of luck with your build. Keep me posted on your progress.
Hello and happy spring! We just dug out our 6 raised beds that were previously filled with dirt from our property We’re doing it right this time, thanks to your helpful guidance. I have my Peat Moss and Vermiculite, the last thing I need to decide on is which bulk compost to buy from our local provider. They have a Steer Blend: aged mulch,steer manuer,bath fines and sand, or should I just get the Steer Composted Organic? Thanks so much!
If you are planting soon, you will want to have the already composted type. If there is an organic option, that is a great choice as well. Best of luck with your beds!
Hello,
I am new to gardening and I was wondering if I calculate the peat moss as compressed or decompressed when doing 1:1:1 mixture? I was also wondering how much this mixture makes as far as cubic feet. Please let me know. Thanks!
-Drea
Hi Drea – use the ‘decompressed’ number to calculate how much you will need. Add the numbers together and that will give you the total amount in cubic feet. I hope that helps. Good luck and happy planting.
I found the same Vermiculite on a website called Greenhouse megastore.com. Better price than Amazon
That’s great. Thanks for the tip.
Hello, I want to make raised garden beds but not for vegetables, I want them for flowers. I have a very bare backyard and I think they would look really nice back there but all I find is is for vegetable gardens. Any suggestions on raised beds for flowers?Syl
This same soil mix works great for flowers too!
Hi, I know SFG says 6 inches of soil. How many inches of Mels Mix do you use? I’m a new Phoenix gardener. Trying to figure it out.
My first beds were only 6 inches – it is possible to grow in them. I’ve found with our heat, 15 inches is a great depth. There is more soil, water, and nutrients available for the plants and the beds don’t heat up as quickly.
Thanks so much. Glad it was helpful.
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.
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.
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.
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!
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??
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.
I noticed “low desert” is mentioned. Is this mixture good in Prescott, AZ
This mixture is great anywhere.