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.