Have you ever noticed how some potting mixes sparkle in the sun? That’s because they contain vermiculite, a soil amendment that helps with water retention, aeration and nutrient exchange. Vermiculite is a phyllosilicate mineral that is mined from rocks formed 1.5 to 3 billion years ago. Crude untreated vermiculite is used in a variety of industrial materials. The garden variety of vermiculite is called “exfoliated” vermiculite, which has been treated with extreme heat and pressure to force it to expand. This process creates a porous surface that is great for retaining moisture and nutrients. In the past, some vermiculites contained asbestos. However, those contaminated mines were shut down and modern vermiculite is rigorously tested to make sure it is free of this carcinogen. Vermiculite is a non-toxic mineral that will not deteriorate in your soil, so its effects last for a long time. Since it does not break down, it is not useful as a source of nutrients. Instead, it is a structural helper for your soil. Its unique shape traps water and nutrients, which can be extracted by plant roots as needed. This means you need to water less often than you would with soil that does not contain vermiculite.
What is the Benefit of Adding Vermiculite to the Soil
Using Vermiculite in the Garden and Landscape
Vermiculite is used similarly to perlite, pumice, biochar and rice hulls. Each has its own pros and cons, and they can be used in combination to get the most benefits. Compared to these other soil amendments, vermiculite is best for areas and plants that require plenty of moisture, as it has the best water retention. It is not as good at aerating as perlite, so for heavy soils you should use perlite instead or in combination. Since it doesn’t break down like rice hulls, it is good if you want the benefits to last multiple seasons with a single application. Give your plants some vermiculite and grow organic for life!