How To Make Your Own DIY Potting Mix & Garden Bed Soil

Container Garden, Garden Tips, Techniques

Here at Frosty Garden, we make a lot of our own soil.  Making your own garden soil is a really easy process.  At a certain scale, it’s also much less expensive than commercial soil bags you can purchase at the store.  Here we’ll teach you our techniques and methods.

When you understand the components of a good garden mix, it can open a lot of doors for you.  You will know how to improve almost any soil that you might be working with.

When Should You Consider Making Your Own Garden Soil?

The bottom line, whether you buy soil or make your own, it’s not the most inexpensive of endeavors.  As it turns out, “cheaper than dirt” isn’t very cheap at all!

The honest truth is if you only need a few cubic feet of soil, you are much better off just buying the soil you need.  You will end up spending far more on the components to make your own soil than you would those few bags purchased from the garden store.

If you need a lot of soil, either for a container garden or to fill a raised bed, that’s the point when making your own soil might be worth both the time and the money.  In these applications, you often need quite a bit of soil, which translates to quite a few bags of potting mix.

A general guideline you can use is if you would be spending more than $100 in potting mix bags, you probably should consider making your own.  The materials to build your own soil, in sufficient bulk, will usually be similar at that point.  When you make your own, you can get a lot more of it for the same amount of money.

What Characteristics Make For A Good Potting Soil?

There are some characteristics that you want to see in a good quality potting soil or garden mix.  In general, a quality soil that will help your plants thrive has the following characteristics:

  • Plenty of nutrients for your plants initial growth
  • Drains water well / Non-clumping
  • Retains moisture
  • Healthy pH for plants

Good quality potting soil will compress together and hold its shape without breaking apart.  It should also crumble apart with only a minor amount of pressure applied.

What you definitely don’t want to do is dig up a bunch of dirt from your yard and try to use that in your garden!  Your average dirt will have almost none of the above characteristics and will offer you more troubles than it’s worth.

Additionally, what is commonly known as “garden soil” is also not good for the purposes of growing plants.  Garden soil can be used as an element in a soil mix, but it shouldn’t be used exclusively.

What Are The Major Components Of Potting Mix?

As mentioned above, you are looking for certain characteristics in your potting mix.  We’ll go through these one by one and give some examples of materials that you can use to create those characteristics.

Nutrients

  • Compost
  • Worm castings
  • Fertilizer
  • Slow release fertilizers
  • Azomite
  • Greensand

Non Clumping & Drains Water Well

  • Sphagnum peat moss (less sustainable)
  • Coco coir (more sustainable)
  • Vermiculite
  • Perlite
  • Sand
  • Composted wood chips
  • Rice hulls
  • Brewing grains (in limited quantity)

Moisture Retention

  • Sphagnum peat moss (less sustainable)
  • Coco coir (more sustainable)
  • Vermiculite
  • Greensand
  • Compost

Soil Acidity or pH

  • Garden lime

As you might have noticed, some materials provide multiple benefits.  These are particularly good ingredients to use!

Don’t Worry Too Much About Soil pH!

We were hesitant to mention pH, simply because that can turn a lot of people off from making their own soil.  “It sounds complicated!”, they’ll say.  We agree.

Here’s the thing.  Plants are quite good at growing in soil that has a fairly wide pH.  Will they grow a little bit better with the perfect pH?  Sure.  Will they also grow just fine if the pH is a little off?  Yes they will.  You have a pretty wide range to work in if you’re growing common garden vegetables.

With the ingredients we discuss here, the main one you have to worry about is sphagnum peat moss.  It has a lot of benefits.  It will provide bulk, it breaks down slowly, it retains moisture and it doesn’t interfere with good soil drainage.  But, peat moss is naturally acidic and will therefore tilt your DIY soil towards acidity.

If you use peat moss in your garden mix, it will be beneficial to correct that acidity by raising the pH of the soil.  If you want to correct the pH, you can do so by adding dolomitic lime, more commonly called garden lime.  You can also find calcitic lime, which is basically the same thing with more calcium.  There are two types out there, powdered form and granular form.  Powered forms will tend to correct the pH more quickly, whereas granular does so more slowly and is also generally considered safer to use.

In general, consider adding the following amounts of garden lime:

  • 1 Tbsp per gallon (4 liters) of soil mix, or
  • 1 (heaping) cup per 15 gallons (60 liters) of soil mix, or
  • 3 (heaping) cups per 50 gallons (200 liters) of soil mix

Other than that, you don’t really have to worry about pH.  In many cases, you could probably even skip this step and still be just fine!  Again, this is about trying to get optimal pH and not about just getting plants to grow.

Remember, There Is No Perfect Recipe

There are many ways to go about formulating your own potting mix and garden soil.  There isn’t just one perfect recipe.

We would encourage you to work with ingredients that you have access to.  What do we mean by this?  If you have access to cheap compost, that should be a primary ingredient.  If you have access to free sand or composted wood chips, use that!  Have a local peat moss seller, use them!  If you can’t find one particular ingredient, use something else that provides the same benefit.  If you have more of something, use more of it!

There is a lot of room for experimentation in making your own soil.  That’s certainly one of the benefits of DIY potting soil.  You can make it with what you want and to have the characteristics you want.

Example DIY Garden Soil Mix Recipes

Here are a few of the garden soil recipes that we know about.  We use the “part system” so you can decide what quantity you want to make.  That way, you can base it on gallons, liters, buckets, bushels, or dump trucks for quantities.

As you will see, there are a lot of different ways to go about making various soil mixes!  Also, for all recipes, coco coir can always be substituted for peat moss if desired.

Mel’s Mix from Square Foot Gardening

  • 1 part compost (from 5 different sources)
  • 1 part vermiculite
  • 1 part peat moss or coco coir
  • Garden lime, if using peat moss (~1Tbsp per gallon of mix)

Frosty Garden’s “Secret Weapon” Potting Soil:

  • 2 parts compost (typically homegrown or even humanure)
  • 1 part peat moss (locally sourced when possible)
  • 1/2 part vermiculite
  • 1/2 part perlite
  • Greensand per manufacturer recommendation
  • Biolive per manufacturer recommendation
  • Azomite per manufacturer recommendation
  • Garden lime, if using peat moss (~1Tbsp per gallon of mix)

General Potting Soil

  • 1 part peat moss or coco coir
  • 1 part compost
  • 1/2 part perlite
  • Fertilizer per manufacturer recommendation
  • Garden lime, if using peat moss (~1Tbsp per gallon of mix)

DIY Potting Soil

  • 2 parts peat moss or coco coir
  • 2 parts vermiculite
  • 1 part compost
  • Fertilizer per manufacturer recommendation
  • Garden lime, if using peat moss (~1Tbsp per gallon of mix)

Homestead Potting Soil

  • 2 parts peat moss or coco coir
  • 1 part compost
  • 1/2 part vermiculite
  • 1/2 part worm castings
  • Fertilizer per manufacturer recommendation
  • Garden lime, if using peat moss (~1Tbsp per gallon of mix)

Garden Soil Based Potting Mix

  • 1 part peat moss or coco coir
  • 1 part garden soil
  • 1 part compost
  • 3/4 part perlite
  • Fertilizer per manufacturer recommendation
  • Garden lime, if using peat moss (~1Tbsp per gallon of mix)

Houseplant Mix

  • 2 parts peat moss or coco coir
  • 1 part perlite
  • 1/16 part sand (approximately 3/4 cup per gallon of mix)
  • Fertilizer per manufacturer recommendation
  • Garden lime, if using peat moss (~1Tbsp per gallon of mix)

Cactus Mix

  • 3 parts peat moss or coco coir
  • 2 parts sand
  • 1 part perlite
  • 1 part vermiculite
  • Fertilizer per manufacturer recommendation
  • Garden lime, if using peat moss (~1Tbsp per gallon of mix)

Seedling Mix*

  • 2 parts coco coir
  • 2 parts vermiculite
  • 1 part sand
  • Garden lime, if using peat moss (~1Tbsp per gallon of mix)
  • See below for notes on seedling mixes

Techniques For Mixing Up Your Garden Soil

If you want to make just a few gallons at a time, we have found using a wheelbarrow to mix the ingredients as a good method.  This is obviously a bit limited as you can only mix an amount that will fit in your wheelbarrow.

If you want to make up larger amounts, we recommend laying out your ingredients on a tarp.  You can mix up the ingredients by hand and also use the edges of the tarp to help mix your materials together.  We have used this technique to mix up to about 50 gallons of mix at a time and it works great.  Yes, you get dirty.  This is what gardening is about.

If we had access to a concrete mixer, we would strongly consider using it to help make up soil.  That would make short work of soil building!

What About Making Your Own Seedling Mix?

One of the most important characteristics of seedling mix is that it’s relatively sterile.    This can be difficult for the home gardener to achieve, but it can be done.  The recipe we provided above should be relatively sterile, but it’s not guaranteed.

In general, we would advise most gardeners to purchase seedling mix instead of making their own.  Most commercially available seedling mixes are pre-sterilized.  Seedling mix is also often not needed in extremely high quantities, either.  We buy our seedling mix and we have every one of the needed ingredients on hand.  We go through a large bag every two years, so it’s not really worth our time to make it.

If you want to sterilize your soil, steam is the best technique to use.  What we recommend is heating your soil with steam to about 140-160 degrees and holding that temperature for at least 15 minutes.  There are other techniques out there, but this is the safest method that will ensure good results.

Should You Build High Quality Potting Soil For Raised Beds?

We think this is a good question and the answer is that it’s entirely up to you.  It can be quite costly to purchase all the supporting materials to fill such a volume.

We made our own soil for our beds (using our “secret weapon” described above) and can tell you that we spent several hundred dollars on the soil for our beds.  We looked at it as a long term investment and wanted our beds to produce intensively for years to come.  Our raised beds produce every kind of fruit or vegetable incredibly well, so it was worth it for us.

What we can tell you is that we’ve seen people experience a number of troubles with trying to fill beds inexpensively.  Several vendors around interior Alaska sell what they call “garden soil” and the quality of that soil vastly varies.  Some is just dirt they dug out of the ground, others do make some effort to create a more appropriate garden mix with a mix of dirt and peat moss.  In every case, the garden soil product can be greatly improved.

What we’d encourage you to do is consider the concepts that we discuss in this post that make for good garden mixes.  That garden soil can certainly be a quality component of your total garden bed!  It might be best to combine other ingredients to make a really nice, quality garden bed soil.  If we were going this route, this is the starting point I would use:

Bulk Garden Bed Mix

  • 2 parts garden soil
  • 1 part  compost
  • 1 part perlite
  • 1/2 part sand

If we were looking to improve the above recipe even further?  I would strongly consider adding one part of peat moss or coco coir into the mix to resist clumping and also increase water retention capabilities.  I might also consider adding some vermiculite as well to improve drainage and water retention.  If we were planning to grow intensively in that bed, I would definitely increase the compost up to two parts.

How Much Soil Do You Need To Make?

Warning:  MATH!

It’s a good idea to figure out how much soil you will actually need.  This will help you when planning out how much material to purchase for your project.

In our experience, figuring things out basically by cubic foot has been the most accurate method that we’ve found.  (You can do this in metric, too, but the math will be slightly different.)  Most of the products we discuss are sold by the cubic foot, also making this very easy.

Here are some reference numbers that you might find helpful:

  • 1 gallon container:  0.13 cubic feet
  • 5 gallon bucket:  0.69 cubic feet
  • 10 gallon grow bag:  1.3 cubic feet
  • Raised bed:  Length (ft) x width (ft) x (height (in) / 12)

You can determine how much of each material that you need.  For our example, we’ll assume you are filling a 4 foot x 10 foot x 1 foot raised bed and you’re using “Frosty Garden’s Secret Weapon” soil mix:

First, figure out how many cubic feet of total soil mix you would need:

  • 4 foot x 10 foot x (12 inch / 12) = 40 cubic feet

Then, determine the recipe’s total number of parts:

  • 2 parts compost + 1 part peat moss + 1/2 part vermiculite + 1/2 part perlite
  • Simple addition gets us to 4 total parts in the recipe

For each material, divide the total cubic foot volume needed by the total number of parts in the recipe, and then multiply by the parts needed of each material:

  • Compost:  (40 cubic feet / 4 parts) x 2 parts compost = ~20 cubic feet
  • Peat Moss:  (40 cubic feet / 4 parts) x 1 part peat moss = ~10 cubic feet
  • Vermiculite:  (40 cubic feet / 4 parts) x .5 part vermiculite = ~5 cubic feet
  • Perlite:  (40 cubic feet / 4 parts) x .5 part perlite = ~5 cubic feet
  • Total:  40 cubic feet!

In the event you are ordering materials by the cubic yard, you can figure that out too!  Simply divide the total cubic feet needed by 27 to get the number of cubic yards.  In our example above, we need exactly 1 cubic yard of compost!

Go Forth And Make Your Own Garden Mix!

We hope that this post has been insightful.  If you are looking to build out a garden bed or start a good sized container garden, making your own soil is a great way to get more bang for your buck.

If you have any questions or if we missed something, feel free to slap a comment below!

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