Perlite & Vermiculite Gardens

Perlite

• Perlite, a naturally occurring mineral that forms during volcanic activity, forms from cooling lava and is usually gray or green, although the color can vary. Commercial perlite results from the crushing and heating of the minerals, which greatly increases its volume and porosity. Heating perlite at a temperature of 1,500 to 2,000 degrees Fahrenheit can increase it volume by 20 times. Once heated, the lightweight low-density product becomes valuable for various purposes, including as a potting mix component.

Vermiculite

• Vermiculite, like perlite, also comes from volcanoes and also becomes extremely light and porous when heated. In the case of vermiculite, a temperature of about 570 degrees Fahrenheit is sufficient to alter its composition so that it greatly expands in volume. Treated vermiculite has several commercial applications, including its use as an ingredient in potting mediums. If you purchase vermiculite, make sure its labeled for use as a potting mix. Vermiculite used to insulate houses does not work well as a potting mix component since manufactures often treat it to repel water. Gardeners need their mixes to retain some moisture.

Medium

• Container gardeners tend to use potting mixes with both mineral and organic elements. The mineral ingredients help with the aeration, drainage and water retention of the mix. Perlite and vermiculite have become two of the most widely used mineral substrates in potting mixes for container gardens. A typical recipe for a potting medium might call for 1/2 peat moss and 1/2 vermiculite or 1/3 garden soil, 1/3 peat moss and 1/3 perlite, among many other possible combinations.

Miscellaneous

• You can purchase a commercial potting medium containing vermiculite or perlite or make your own. Your local nursery or garden store should carry everything you need to create the perfect mix for your container garden. If you decide to use garden soil in your homemade mix, pasteurize it first. Heating it at 180 degrees Fahrenheit for a half hour eliminates insects and harmful organisms.