What Are Those White Things In Potting Soil?

3306949169 d2966ac088 225x300 What Are Those White Things In Potting Soil?

If you’ve ever planted something in the store-bought potting mixes, you’ve inevitably asked yourself this question.

What Is It?

The irregularly shaped white pieces that comprise half of most potting mixes is what is called “perlite.”  Perlite is a naturally occuring volcanic glass that is mined all over the world for industrial purposes, as well as for hydroponic farming, and horticulture purposes.  It is considered a silicous rock formation, and formed containing a large percentage of water.  Mining companies that harvest the rock heat the rough chunks of perlite in super heated ovens, causing the perlite, and the water within them, to expand up to 20 times and expload into tiny pieces. The tiny pieces are what we find commonly in most commercial potting soil mixes.

Why Is It Used?

Perlite found a place in the horticulture fields because it is lightweight and capable of storing water while keeping soil loosely aerated.  The reason potting soil remains fluffy and doesn’t smother your plants (like plain topsoil would do) is due in part to these great perlite granuals.

Can I Purchase Perlite By Itself?

For those of you who want to create your own potting mixes with homemade compost, you can buy bags of Perlite at your local home and garden store, or at any nursery. Perlite can also be mixed in with your garden soil to provide better air flow down to the roots, and to help the soil retain water in dry areas.

Photo Courtesy of: breekp

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  1. Heather says:

    I have been stressing about those pesky things. I buy as much organic as I can and I realized they were in all my seedlings I just bought, and my potting soil. I thought they were some man made thing. Thank you for putting me at ease.

  2. doggz says:

    I composted soil for plants and got the same white stuff in it but did not put any of these in it. and it is definatly not a rock compound but soft and white like same stuff found in regular potting soil what is the white stuff i got?


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