Perlite – Perlite is not a trade name but a generic term for naturally occurring expanded puffed volcanic glass. Perlite is a finite resource. It is crushed, heated and expanded lava (actually volcanic sand) that has no mineral nutrients or buffering capacity. It is made like popcorn, moisture trapped in the lava particles causes them to rupture when heated to above 755 °C. Perlite is less collapsible than vermiculite (see next post) and has a neutral pH (approximately 7.0). It is lightweight with a rough surface where it traps molecules of water. It does not absorb water which means it greatly improves drainage but provides minimal water retention. Perlite comes in grades (sizes) with the more course grades being better for larger containers. Perlite is very dusty when dry, and the dust is harmful to your lungs. Always wet perlite before using it, I use a water bottle mister/sprayer to moisten the inside of a bag or if I am making up a big batch of grow medium I put the hose and nozzle right in the big bag and soak it. It is especially good for starting cuttings, sometimes mixed with vermiculite or sand. I have read studies that show good growth with perlite hydroponic systems. Other benefits of horticultural perlite are that it is sterile and weed-free. Indoor growers know its light weight makes it ideal for use as an additive in any container growing. If you use a lot of perlite in with your soil your containers won’t be as heavy. Use too much perlite and they may tip over easy.

Good Growing,
Dr. E. R. Myers

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