Perlite is a highly absorbent substance which can be used as growing media or a added additive to soil or coc growing mediums. Perlite is an amorphous volcanic glass that has a relatively high water content, typically formed by the hydration of obsidian. It occurs naturally and has the unusual property of expanding greatly when heated sufficiently. In horticulture it makes composts more open to air, while still having good water retention properties, it makes a good medium for hydroponics. The expanded material is a brilliant white, due to the reflectivity of the trapped bubbles. In horticulture applications perlite is used throughout the world as a component of soilless growing mixes where it provides aeration and optimum moisture retention for superior plant growth. For rooting cuttings, 100% perlite is used. Studies have shown that outstanding yields are achieved with perlite hydroponic systems.

Other benefits of horticultural perlite are its neutral pH and the fact that it is sterile and weed free. In addition, its light weight makes it ideal for use in container growing.Other horticultural applications for perlite are as a carrier for fertilizer, herbicides and pesticides and for pelletizing seed. Horticultural perlite is as useful to the home gardener as it is to the commercial grower, it is used with equal success in greenhouse growing, landscaping and in the home in houseplants.