Perlite is a volcanic material that is crushed, screened and expanded by heating at extremely high temperatures (1400°F). Perlite is light weight, sterile, and holds three to four times its weight in water. It also provides air porosity to a medium.

Care must be taken when using perlite because the dry dust can be a throat and lung irritant.

Photo of plants growing in trays containing perlite. Close up photo of plants growing in perlite.