Perlite

As a soil amendment, Black Gold® Perlite (a mined volcanic rock that is expanded, similar to microwave popcorn) is used to improve aeration and drainage. Screened for uniformity, its moisture and nutrient retention capabilities and lightweight characteristics make it an excellent sterile medium for starting seeds and rooting cuttings. Perlite does not degrade over time, which makes it a long-term solution to many gardening problems.

In addition to being a potting soil mix component, perlite is an excellent sterile medium for starting seeds and rooting cuttings. Can also be used to store bulbs.