What I am about to share with you is my secret potting soil recipe, so don't share it with more than a few thousand people. O.K.?
First of all, if you done much research on this subject, you'll find that it can get pretty darn complicated. Fortunately for you, I don't like complicated. I'm a simple kinda guy, and my simple strategies have been proven to work really well.
There are only three things that you need to know about potting soil. It should be light and fluffy, it should drain well, and it should be very much organic. Keep that in mind as you gather your ingredients for potting soil.
Having the ability to drain well is really, really important. Plants grown in containers can dry out easily, and therefore should be watered daily during warm weather. So your potting soil needs to drain well. Then no matter how often you water your plants, the excess water drains through quickly.
For the most part, my list of ingredients for potting soil goes something like this:
Skeptical already aren't ya?
Don't be. I've grown tens of thousand of plants in this mix, and they grow like weeds. Now let me show you how I go about taking my ingredients for potting soil and turning them into potting soil.
For the decomposed shredded hardwood bark mulch what I do is buy a few yards of the oldest, finest mulch that I can find. I shop all the mulch suppliers in our area to find the finest, darkest hardwood bark mulch that's out there. As hardwood bark mulch decomposes it gets finer, and it gets darker. Hardwood bark mulch is pretty common here in northern Ohio, but if you can't find it in your area you'll have to improvise.
Keep this in mind as you gather your ingredients for potting soil. The only thing that Mother Nature provides for her plants is decomposed organic matter. That's it. We know it as topsoil, but all it is is decomposed organic matter, and depending on what part of the earth you are on, it's made up of different types of organic matter.
So if you can't find hardwood bark mulch, find the next best type of organic matter.
I buy the hardwood bark mulch at least a year ahead of time so it has even more time to decompose. I just put it in a low flat pile so it can get wet all the way through when it rains. This helps to speed the decomposition process. The secret is to always have two to three yards more than you need on hand, that way you've always got some decomposing.
The hardwood bark makes up the bulk of my ingredients for potting soil. Then if I have coarse silica sand that has to come out of my propagation bed I just pile that on top of the hardwood bark mulch. You don't have to have the sand, so if you don't have any don't worry about.
Then I empty one of my composting bins and put the organic material that I take of the compost bin right on top of my potting soil pile, which is starting to look like a Dagwood sandwich. (that's from an old newspaper cartoon) Because I use my Lazy Man's, No Turn Composting Method" some of the material coming out of the bin isn't broken down completely. But it can continue "cooking" right in the potting soil pile.
Then, just before I start using my potting soil I go to the gravel yard and get a yard or two of small silica stone, and dump that right on top of the potting soil pile, adding one more layer to my Dagwood sandwich.
I use slica sand and silica stone because there happens to be a silica quarry in our area, so the material is available, and it is affordable. Chances are you may not find silica stone where you live.
Just use what's available in your area, as long as the stone is hard enough that it won't break down and alter the PH of your potting soil. Don't use limestone, it is very alkaline and it will alter the PH of your soil. Use something very small and hard, and as neutral as possible.
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Do you really need the stone? No, you can remove the stone from your list of ingredients for potting soil. The only reason that I add it is because I water daily with overhead sprinklers, and I want to make sure that none of my plants are getting too wet.
Since I use a lot of potting soil, I start out with about 9 cubic yards of hardwood bark mulch, so as you can imagine, the pile is quite large by now. By now your probably wondering how you are going to mix this huge pile. You're not going to.
Keep in mind that our pile of ingredients for potting soil has been added in layers, so it looks like a sandwich. So what I do is take a pitch fork and take one little corner of the pile and spread it out a little, then I run over the material that I have spread out with my roto tiller. Then with a shovel I toss what I just roto tilled back up on the middle of the potting soil pile.
This pile of potting soil does look like a sandwich because as we added the stone to the top of the pile is spilled down over the sides, but there actually are about 4 different layers of material in this pile. As we start taking soil out of the pile you can clearly see the many layers.
Then I take the pitch fork again and knock down some more material from the place I did the first time. By now I'm getting a little deeper into the pile, and I'm getting a pretty good mix of all the materials in the pile. Once again I run them over with my roto tiller. If it looks like a pretty good mix I use it for potting. If not I toss it up on top of the pile and go just a little deeper and repeat the process. By now I can surely use what I mixed up.
As you can see, with just a little mixing and tossing the mixed soil on top of the pile we quickly have plenty of usable potting soil without having to mix the entire pile all at one time.
And that's about all there is to my potting soil mix, and as I mentioned earlier I've grown and sold tens of thousands of plants using this system. If you're potting smaller plants and have too much large material in your mix you can just sift it through a piece of heavy duty hardware cloth (screen). Just take what doesn't pass through the screen and toss it back in your compost bin and let it break down further.
Once you get a pile of potting soil like this going, just keep adding to it each year. Eventually you will have an ample supply of beautiful potting soil. You can use it for potting, and you can also use it in your flower beds.
Now I know that somebody is going to write to me and say; "Mike, how much stone, how much bark mulch, how much compost? What is the ratio?" Here's the answer to that: I don't have a clue. It's not all that important. Just make sure your potting soil contains fluffy, well composted organic matter, and that the soil drains well.
Once I pot my plants I fertilize them with a 14-14-14 slow release fertilizer to make up for anything my soil might be lacking.
Ingredients for potting soil options...
If you live in an area where rice hulls are plentiful, you can use rice hulls in your potting mix. If you live in an area where pine bark is plentiful you can use pine bark.
Just make it really nice organic potting soil that drains well and your plants will love you for it.
There you have my "secret" ingredients for potting soil.