Vermiculite and perlite are lightweight substitutes for sand in soilless planting mixes. They are also frequently used to improve the texture and aeration of potting soils and garden soils.
What Is Perlite?
Perlite is volcanic rock that has been crushed and heated until it explodes into small white pieces. Its capacity to hold water is rated as medium, while its capacity to hold nutrients is rated as low.
What Is Vermiculite?
Vermiculite is a magnesium-aluminum-iron silicate. It resembles mica with stacked layers that trap water. Its capacity to hold water and nutrients are both rated as high.
Vermiculite and perlite are odorless and sterile, which means they are disease, insect and seed free. Neither one deteriorates or rots. They are used in soilless potting mixes and potting soils for seed cultivation, propagation, transplants, containers and hydroponics. They are also used in dry fertilizers, herbicides and pesticides as carriers to improve coverage.
Perlite improves the drainage of soil and soilless mixes, while vermiculite holds water. Perlite helps insulate plant roots against extreme fluctuations of temperatures.
Vermiculite is used as an anti-caking material in dry pesticides and fertilizers. Perlite is used as coating on pelleted seeds.
Vermiculite does not contain asbestos nor is it a form of asbestos. Vermiculite from a mine in Libby, Montana, was found to be contaminated by asbestos and the mine was closed in 1990. Since then vermiculite from all other mines has been tested and found to be clear of asbestos. Vermiculite is considered safe to use in personal and commercial areas.
- Perlite Institute
- Vermiculite Association
- Home Harvest Garden Supply
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About this Author
Melody Lee worked as a newspaper reporter, copywriter and editor for 5 years. In addition, she has edited magazine articles and books. Lee holds a degree in landscape design and is a Florida master gardener. She has more than 25 years of gardening experience, which includes working at nurseries and greenhouses.