Grow Better Plants with Homemade Potting Soil

Put DOWN that bag of Miracle Gro potting soil. It’s just a wildly priced mix of peat moss and synthetic chemicals.  This year get your hands dirty and make your own earth friendly, nutrient rich potting soil with a few easy to find ingredients.

Why make your own potting soil? Because it makes you cool and gives you green thumb credibility over everyone else who doesn’t. I mean, that’s the main reason. Picture it; there you are talking small talk with your neighbour or cell mate and you casually whip out the whole “Well, I’d better go, I’m just finishing mixing up a new batch of potting soil and I don’t want the perlite to dry out”.

Perlite doesn’t dry out, but that doesn’t matter because they didn’t hear anything beyond the fact that you are mixing up your own potting soil. Gold star and immediate adoration all around for you.

The second reason to make your own potting soil is it’s cheaper and a better product than you can buy in a bag. 

And it makes you cool. I mentioned that right?

This gardening season I am upgrading to planting in SOIL BLOCKS. Compressed blocks of soil that eliminate using pots at all. NO pots. Just weirdly firm blocks of earth with plants sprouting out of them.

I’ll be talking more about soil blocks next week, but they do require a special type of soil mix to make them out of.  This is that soil. This potting soil recipe can also be used as your regular potting soil for containers, pots and seedlings.

This soil block mix is based on Eliot Coleman’s soil block recipe. If you haven’t heard of Eliot Coleman, he and his wife are the King and Queen of alternative gardening methods. And by alternative I mean alternative to factory farming. If this is your first introduction to Eliot and you’re intrigued, I recommend that you take a look at his first book Four-Season Harvest.  I kind of demand it actually.

Here we go …

Potting Soil Recipe

FOR SOIL BLOCKS and more.

 

Clockwise from upper left (Peat moss with spoon of required lime on top, Perlite, Garden Soil, Natural Fertilizer, Compost.

INGREDIENTS & WHY

Peat Moss or Coco Coir

  • for holding moisture & adding bulk and airiness

One ingredient into this and we’re already in a debate. Peat Moss. A farmed, organic material that holds moisture and makes up 80% of most store bought potting mixes is from Canadian bogs  and is being over farmed and distributed. Peat Moss takes THOUSANDS of years to form. Therefore even though technically it is a renewable resource, our demand for it has far exceeded the rate at which it forms.

Although I personally feel it is superior to Coco Coir (which dries out more quickly) people are now encouraged to switch from Peat to Coco because fo the environmental impact of over harvesting peat to the point of near depletion.

Coco Coir on the other hand, is inexpensive to produce, is truly renewable and works very well.  BUT environmentally, it has to travel from it’s #1 producing country – Sri Lanka. That’s a lot of jet fuel if you’re in North America.

I’ll leave the choice up to you.  I use both coco coir and peat moss. For potting soil like this I still use peat moss.  For bulb storage, root vegetable storage and any other instances that I used to use peat moss I now use coco coir. 

Lime

  • for pH balance.

If you’re using peat moss (which has an acidic pH) you’ll need to add a bit of lime to it to offset the acidity.  You do not have to add lime to coco coir which has a balanced pH.

Perlite

  • For improved drainage and water retention.

Perlite is puffed up volcanic rock.  It’s heated until it burst into a styrofoam like ball, like popcorn!

 

Native Garden Soil

  • for added beneficial bacteria and health.

Native garden soil is just what it sounds like. Garden soil native to where you’ll be growing. As in a bucket of dirt from your garden.

This is a less common ingredient in potting mixes, but adding it to your potting soil blend  makes a lot of sense to me. I have ZERO idea if plants have any sense of familiarity but to me it seems like a good idea to get your seedlings used to the surroundings they will have once you plant them out in your garden. Plus your native soil has all kinds of beneficials in it like nutrients, microorganisms, bacteria and other small critters.

Natural fertilizer (no synthetics)

  • for nutrients

You can mix your own blend of fertilizer out of equal parts Greensand, Phosphate Rock, and Blood meal.  I chose to go the easy (and slightly cheaper route) by using Gaia Green All Purpose premixed natural fertilizer which has the MOST interesting list of ingredients on a fertilizer I’ve ever seen – Feather meal, alfalfa meal, bone meal, blood meal, glacial rock dust, natural rock phosphate, fishbone meal, mineralized phosphate, potassium sulphate, insect frass, basalt rock dust, humic acid, gypsum, kelp meal, oyster shell flower, greensand.

Compost

  • For nutrients, water retention, and beneficial microbes.

If you don’t compost yourself, although it’s easy here’s how, you can buy bagged compost.

 

The Recipe

 

What you need:

  • 10 quart bucket
  • 1.5 buckets of peat moss
  • 1/4 cup lime
  • 1 bucket perlite
  • 1.5 cups fertilizer
  • 1/2 bucket native garden soil
  • 1 bucket compost

To make your life easier use a basic metal bucket and measure 40 cups of water into it. MARK THE BUCKET WITH A LINE on the inside and the outside. 

This is your 10 quart mark.

When the recipe calls for a bucket of something, fill it to the line and you’ll always have the right measurement.

Mix and store this recipe in a 80 litre (20 gallon) tote.

  1. Mix 1.5 buckets of peat with 1/4 lime and mix.
  2. Add in 1 bucket of perlite.
  3. Add 1.5 cups of fertilizer (either equal parts blood meal, rock phosphate and greensand or an all purpose natural fertilizer like I recommend).  Mix thoroughly.
  4. Add in 1/2 bucket of garden soil and 1 bucket of compost.
  5. Mix everything well.

You now have a nutrient rich potting mix for seedlings, potting and plants. Because YOU are cool. I mean, if you’re making your own potting soil you surely have a handle on all manner of things in your life. You’re never late, your finances are in order, you are probably that one person who actually DOES have more than 24 hours in your day.

So why shouldn’t you use Miracle Gro products like their potting soil? Well, here’s the thing about Miracle Gro; as a fertilizer it isn’t bad, but as an environmental choice it’s iffy. For one thing there’s damage from under-utilized chemicals remaining in the soil and becoming runoff into streams and oceans. 

Miracle Gro was also closely associated with the now defunct Monsanto. 

And Monsanto – unlike you – was decidedly not cool.  

(Monsanto was bought by Bayer in 2018 and much of its agricultural/seed holdings were sold off)

Make wheelbarrows full of this homemade potting mix for the price of a couple of small bags of it. Based on Eliot Coleman\'s soil block potting mix made with peat or coco coir, perlite, compost, garden soil and natural fertilizer.

33 Comments

  1. Heidi says:

    I have been using Elliot Coleman’s “recipe” in soil blocks for years! I love it. In zone 4b (south eastern MN), I have to make sure I have all my ingredients for next spring BEFORE this summer is even in full swing. The stores won’t be ready when I am-even without a pandemic.

  2. blue says:

    I grow my plants like I cook my food, mix in a little bit of everything.

  3. Kunyi Mangalam says:

    Hi karen,
    Thanks for this. I’ve just made the tiny little soil blocks for germinating the seeds, and then will plop them into the larger soil blocks that require the potting mix that you’re whipping up. Question: what is green sand?

  4. Erin G says:

    When making the smaller blocks it really helps to have screened the peat to take out the largest chunks (1/4″ mesh.) I learned this in hindsight, of course.

    I’m switching about half of my market garden starts to soil blocks this year after dinking around the last few years trying them out on lettuce. Transplanting goes so much more quickly without fumbling around popping cells.

    • Karen says:

      That’s right. I’ll add that. If you buy *really* good peat it’s already sifted and very fine, but most regular bags of peat moss and coir are a bit chunky. I would have to say from my limited experience that soil blocks have improved my germination rate by a billion. Give or take. ;) ~ karen!

  5. JANE JACOBSEN says:

    Thanks for bad mkouthing Monsanto. They deserve it.
    I garden in big 4′ x 12′ x 10″ raised bed planters. It takes a LOT of soil. I buy big (11 kilo) blocks of coir (washed to remove the salt). Put two of them in a big Rubbermade tote sitting in each 1/3 of the planter. Fill the totes with water and let soak overnight. In the morning overturn the totes into the planter. For each division of the planter, dump in 2 bags of mushroom compost or the equivalent homemade composy. Then dump in 2 bags of garden soil. Mix the whole shebang. Be careful of your source for the soil. The cheapo stuff from the big box stores is full of weeds. I get mine from a reputable nursery. This is a bit expensive but it will last for years with a topping of fresh compost every year and I can’t possibly dig enough garden soil to fill those big planters.

  6. Edith says:

    I can’t believe it. I always thought that Perlite was just a fancy name for styrofoam particles. I’ve been feeling guilty for nothing!

    • Karen says:

      That’s O.K., I’m sure you have reason to feel guilty for some other reason. :) LOL! ~ karen

    • Lauren says:

      I knew what they were but I hate the little white perlite things. I understand their purpose, but I still loathe them, so I don’t use them. It’s like having bits of lint in your pots, then if you want to re-energize the soil from year to year, you have them in your compost. I had to give up compost because a local black bear tore apart my compost bin. I compost in a ‘general’ yard waste pile far, far away from the house now, and don’t use it for myself.

      Love having a ‘recipe’ for homemade potting soil though so thank you!

    • Lynell says:

      I thought the same thing. We learn something new every day! LOL

  7. Jane says:

    A word on coconut coir: some product has too much salt because the harvest was washed in saltwater instead of fresh water. As a growing medium, the salt deters uptake of water by plant roots.

  8. Teresa says:

    You are decidedly cool. But how do you make the blocks??

    • Teresa says:

      Oh- I see. You’ll be telling us next week. I’m probably not the only one that skimmed over that part. Maybe you should put your “more info later” teasers in bold for the skimming bozos like me. I did order the book (used) so I can read it and pretend I’ll be a better gardener this year.

    • Karen says:

      I have a whole post dedicated to making the soil blocks coming up on Monday, March 30th. :) ~ karen!

  9. Sachi says:

    Hello from Sri Lanka karen! <3

  10. Wendy says:

    I should have sourced all these ingredients before the world shut down. I have a box of flower & vegetable seeds without a fresh pot of soil to plunk them into. It will be a late harvest 🤷‍♀️

    • Karen says:

      If you want to get going and you have nothing, see if you can just find some garden soil to shovel up. Sand can be used in place of Perlite as well. ~ karen!

  11. Connie says:

    Great recipe. I also love Gaia Green 444 fertilizer. I just want to share that when using Perlite it is dusty and not good to breath in so to protect your lungs wear a mask or moisten it before scooping.
    Happy gardening, especially during this uncertain time.

    • Karen says:

      You’re right! I meant to put that in the post. To wear a mask or a tea towel tied over your face. Both the perlite and peat moss are incredibly airborne. ~ karen!

      • Lez says:

        Everyone is wearing masks anyway!
        Could be cool going to the last supermarket open to buy the last rationed toilet roll with a tea towel tied around your face! :)

  12. Love any environmentally-friendly alternative! Thanks Karen.

  13. Kmarie says:

    What if you don’t have compost?

    (Also I’ve seen you mention before that adds are based on our searches which is hilarious to me because I keep getting an ad for a seniors call button and how to wear make up over 50- which is cool except I’m 36. 😂🤷‍♀️😂)

    • Karen says:

      Hi there you 50 year old makeup wearer! Compost is pretty important to the mix. You can buy bags of compost in the same places that you’d buy peat or coco coir. Amazon even sells compost. But if you don’t have it and can’t get it you have two options. Drive around looking for horse farms. They often have bags of composted horse poop for free or for cheap, usually by the side of the road.

      If you can’t do that just leave it out and use garden soil in place of it. Your soil will have less goodness in it but it will still work as soil for starting plants etc. ~ karen!

  14. Angela says:

    Ok, this post was great all by itself. But…I am *dying* to know if you are going to make your own “soil-block-maker” (and share instructions of course!!!)
    The pre-made ones I’ve seen are insanely expensive for what they are – but so far I haven’t been successful in making my own..
    PLEASE say you’re going to make one and show us how to do it!!! 🙂

    • sideroad 40 says:

      I’m also dying to know…..please don’t make us wait…it’s time!!!!!

    • Karen says:

      Hi Angela! It’s possible to make your own soil blocker, it just isn’t going to be as fast or easy to use as a professionally made one. Basically all you have to do is press soil into a square form and then bang it out. But if I have the materials on hand here, I’ll try to do a tutorial for everyone because I KNOW how expensive the soil blockers are! Crazy. I put off buying them for years but finally succumbed. ~ karen!

  15. billy sharpstick says:

    Will this scale up? I need a couple tons. (My neighbor has a goat farm and a
    has allowed (nay, begged and pleaded) me to come over and shovel up as much goat poop as I want. The layers a foot or two down are very well aged and the plants seem to like it.) Shoveling is good exercise, too.

    • Karen says:

      That’s alotta poop to shovel. Maybe ask him if you can just come over and plant your garden directly onto his pile of poop.😆~ karen!

  16. Martina says:

    Mom’s homemade garden soil recipe was cheapest store bought soil, peat moss and home grown-compost. Can’t remember ratios. The family referred to it as Hanford soil because things grew so well in this mix that it was like they were nuclear powered.

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