Perlite is a naturally occurring compound that almost looks like popcorn. This white-colored lightweight substance is used in gardening. This is because Perlite aids in soil aeration and water retention, the two most common problems vegetable planters face. Perlite is more common in soils where the plant does not thrive in wet or even moist conditions. Examples are cactus and other succulents that do not even need soil but a potting mix.