Perlite in Potting Soil

What Is Perlite?

• Perlite is a volcanic glass that expands when heated to 1600 degrees Fahrenheit, according to Iowa State University. When this volcanic glass is heated, it expands 13 times larger than its original size. When gardeners closely examine perlite, they notice crevices and cavities on its surface. This rough texture locks in moisture on the outside of the glass. Because of its ability to hold in the moisture on the outside, it doesn't weight down the soil.

How Perlite Is Used

• Perlite is used in potting soil for its ability to keep the soil loose, prevent soil compaction and offer plant roots moisture, according to Iowa State University. Gardeners also use perlite to help root their plant cuttings. To root cuttings, fill 1/3 of a plastic bag with perlite, as suggest by Iowa State University. Add water to moisten the perlite. Press a 3- to 4-inch cutting into the perlite, so that the perlite reaches the plant's node or where the lowest leaves meet on the cutting. Blow into the bag and leave it in a place that receives indirect sunlight. Wait two to three weeks for the cutting sprout roots.

Making Potting Soil

• Gardeners make their own potting soil by mixing 1 part peat moss, 1 part loam and 1 part perlite, according to the Iowa State University. Peat moss contributes proper drainage, loam imparts important nutrients and perlite keeps the soil from getting weighed down. When mixing up your own potting soil, use loamy soil that is sterilized. Garden soil can harbor harmful pathogens and pests; therefore, it should not be incorporated into your soil.

Disadvantages of Perlite

• Despite is many benefits, perlite offers some disadvantages. Gardeners should always wear masks when handling perlite. This volcanic glass is dangerous to breathe in. When using perlite, make sure that you are outdoors. Furthermore, perlite rises up through the potting soil when it is watered, according to Pennsylvania State University Extension. Gardeners may have noticed the white glass floating on top of their potting soil. Not only does the perlite on top of the soil decrease its effectiveness, but it also ruins the aesthetics of the surface of the soil.