A common mineral used in horticulture and home gardening, perlite is a lightweight growing medium that has many beneficial properties as a soil additive. Most houseplant mixtures use perlite, a white, fluffy volcanic rock, for soil conditioning, which involves adding material to soil to improve the plant's growing environment.
Perlite is a mineral that looks like clumpy snow or tiny chunks of styrofoam. It is most often found in indoor plant potting mixes or on its own as a soil additive in your local garden section. It can be found in wall insulation and water filtration systems, and as an abrasive in hand washes.
Perlite is a mineral that does not come from a plant or animal, so it is considered to be an inorganic material. Perlite is a volcanic glass that expands into a puffy material when heated to 1600 degrees F. Perlite doesn't soak up or hold water, but water clings to the outside of its particles. When water is added to perlite, the expanded volcanic mineral floats. Some plant food companies add fertilizing nutrients to the mineral for an added boost to plants.
Perlite can be used to improve the permeability and drainage of soil made primarily of dense materials like clay or silt. Clay and silt have small particles that stick together and hold water in the soil preventing drainage. Adding an aerating material like perlite to dense soil conditions the soil and adjusts soil properties to help get oxygen and fresh water to plant roots.
Add some perlite to a large, heavy planting pot to reduce its weight while improving soil drainage. Using the expanded mineral in a soil mixture significantly decreases the total weight of the potting mixture. Perlite is a surprisingly lightweight substance which makes potted plants, especially large ones, noticeably easier to handle.
Perlite is commonly used as part of a soil-less growing medium for greenhouses. When used in this application, perlite is often mixed with an organic material like coconut coir, which is a moss-like additive made from the strong fibrous material that surrounds the hard part of the coconut shell.