Perlite is mined volcanic glass. It's formed into a grow medium when it's rapidly heated, at more than 1,600-degrees Fahrenheit (871 degrees Celsius), causing the perlite to pop like popcorn and make countless tiny bubbles.
Perlite is most effective in hydroponic growing when used with vermiculite - in a 50-50 proportional mixture. This is because perlite is an effective aerator and vermiculite is an effective water absorber. When used in conjunction with one another, perlite and vermiculite offer the perfect balance of water, nutrients and oxygen for the roots of hydroponic plants.
Vermiculite (scientifically called: hydrated laminar magnesium-aluminum-ironsilicate) is also a mined material. Vermiculite closely resembles mica rock and it's shiny, golden flecks can soak up to 3 to 4 times its weight in water. Vermiculite is inexpensive to use as a hydroponic medium. Another reason why vermiculite is so popular among hydro growers is because it attracts calcium, magnesium, potassium, and phosphorous - minerals that are most vital to plant growth.
There is only one disadvantage to using vermiculite alone in a hydroponics system. When used by itself vermiculite retains far too much water and will suffocate plant roots in any growing system. This is why the 50-50 mixture of perlite and vermiculite must be measured out exactly and monitored closely when used as a hydroponic medium.
Both perlite and vermiculite are typically sold online, in 2 -pound bags, for approximately $4.
