Potting Mix or Potting Soil? Peat Moss or Coconut Coir?

Posted on May 29 2009 - 6:23am by Mike Lieberman

First off, from what I can tell there is no difference between potting soil, potting mix and transplant mix. It’s all the same thing just different names.

The reason that you want to use potting soil is that it allows for aeration and water to flow. If you use traditional soil in a self watering container, the roots would get too compact and not be able to grow. That’s no bueno.

Of course it isn’t that simple, there are different kinds of potting soil. There is one that is peat moss based and one that is coconut coir based.

Not being sure which to use, I decided to use both. Screw it why not? That’s part of this whole experience. Trial and error to find out for myself what works best.

Besides the base, the other ingredients are pretty similar. They are vermiculite, compost and some kind of mineralization.

The vermiculite makes the mix lighter and allows for better aeration. The compost provides the nutrients and the minerals, well they provide minerals.

So I bought some 20lb bags of New York Paydirt Potting Soil from the local Lower East Side Ecology Center.

This is coconut coir based, which according to the label is “a sustainable alternative to peat moss.” From some of the articles that I read coconut coir retains water, which is bad for self watering containers. I guess I’ll find out.

I also bought ingredients to make my own organic potting soil – sphagnum peat moss, vermiculite and garden lime. This was mixed up with the compost that I made in my kitchen.

So instead of reading 100 different arguments on which kind of soil to use, I’ll use both and see which one works best and so will you.

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  • http://www.squidoo.com/graceonline graceonline

    One thing most folks don't realize is that much commercial potting soil is heavy with mineral salts. My university soils prof years ago told us that the salt content, as well as pH and nutrient content varied greatly from brand to brand, but also from bag to identically-marked bag within each brand. They tested dozens of brands and found the variability to be, ahem, consistent. He said that he personally washes every bag of commercial soil he buys to wash away the salts. He soaks the soil in three tubs, one after the other, over a period of days, then drains and dries it over fine-mesh screens in the sun.

    As an apartment dweller in the city, I don't have access to space to wash, drain and dry my soil. Luckily, I've found one brand that performs well, container after container, year after year, but it's very difficult to get in San Francisco. That's Martha Stewart's potting soil, and it's sold only at K-Mart. Whenever I'm in the valley and I find it in stock, I buy every bag they have. It's worth it.

  • Mike Lieberman

    Thanks for the comment. Interesting story about your professor. That seems like a lot of work.

    Luckily for me, the potting soil that I used was made at a local ecology center that I trust is mixing things properly with the right amount of nutrients.

    As for making my own potting soil, it was definitely a chore in my city apartment. It was much easier to do in a bigger tub (space permitting).

    Part of the fun of this for me is experimenting and finding out what works best.

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  • Ken McRae

    Nice experiment. Can you link me to the page where you've updated this info and posted the results of this test? Please e-mail me the link. I'd like to see what you found out. Thanks.

    Ken McRae

  • Mike Lieberman

    Thanks Ken. Will do. Likely going to come in the next few weeks.

  • Name

    Coir is simply a by product whereas peat moss is the direct result of habitat destruction. Plus u, Coir doesn't have that chemically thing like peat moss, its a neutral. Just make sure to flush it with water a few times, it tens to have an initial alkalinity.

  • Mike Lieberman

    Thanks. The local mix that I was using had the coir and everything all mixed together. Made at my local ecology center.

  • jim w

    Ya I've been trying to figure out what potting soils the best and I still have Iot. I tryed everyone and I stll think MG with moisture performs the besr providing you mix it up good before you put it in the pot and don't pack it . Leave it nice and fluffy. I have tryed 8 diffrent kinds of P.S. and sometime I still can;t make up my mind.

  • Mike Lieberman

    For the upcoming season, I'm planning on making a boatload of my own compost and getting mad seaweed and horse manure. Hoping all that will help as well.

  • jim w

    Ya I've been trying to figure out what potting soils the best and I still have Iot. I tryed everyone and I stll think MG with moisture performs the besr providing you mix it up good before you put it in the pot and don't pack it . Leave it nice and fluffy. I have tryed 8 diffrent kinds of P.S. and sometime I still can;t make up my mind.

  • Mike Lieberman

    For the upcoming season, I'm planning on making a boatload of my own compost and getting mad seaweed and horse manure. Hoping all that will help as well.

  • Ivriniel

    Having seen the results of peat extraction firsthand, I am only using Coconut Coir in my garden.

    Extracting peat is akin to clearcutting a forest. Forestry companies that engage in clear cuts will go on and on about how they replant the forests, but the fact remains that the forests that grow back after a clearcut are nowhere near as diverse as the forests they replaced.

    It’s the same thing with peatlands. The peatlands we have currently took about 10 000 years to develop after the end of the last ice age.  You are not going to restore them on anything approaching a human time scale, so therefore Peat extraction is not a truly sustainable activity.

  • http://www.UrbanOrganicGardener.com Mike Lieberman

    Thanks for the info. Def something to consider.