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How to Garden With Perlite

By Marie Mulrooney ; Updated September 21, 2017

Perlite is a pH-neutral, sterile, safe-to-handle volcanic mineral. Perlite is prepared for gardening use by super-heating it until it expands to more than ten times its original volume. The expanded perlite is full of tiny air bubbles, and its dimpled surface area helps trap moisture. Mixing perlite into your soil, whether it’s in a garden or for container plants, helps aerate the soil, protects against extreme climate fluctuations, protects against over-watering and makes moisture readily available to plants. Perlite is available in multiple grades, all of which work well for gardening applications, but fine grades of perlite are preferred for use in outdoor gardens. Plants that require well-drained soil will usually do very well in mixes that contain perlite.

Loosen the soil in the rows you intend to plant, working it as deep as necessary for the plants you’re placing in each row--usually between 6 and 12 inches deep. To work the soil, use a rototiller for large areas and a gardening fork for smaller areas.

Spread a 4-inch layer of fine horticultural perlite over the area to be planted. If you're covering a large area, pour out a pile of perlite every few feet and use a rake to help spread it out into a reasonably even layer.

Work the perlite into the soil with the same tool you used before to work the soil.

 

Things You Will Need

  • Rototiller or gardening fork
  • Horticultural perlite

Tips

  • You can also use a combination of one part perlite to one part ground sphagnum moss in the same way, but adding the moss is not necessary; perlite works quite well on its own.
  • To use perlite in planters or containers, you can either mix pure perlite or one part perlite, one part sphagnum moss and one part composted wood shavings in to the soil, then plant as usual. Make sure to check soil dryness frequently as perlite mixes may dry out sooner than non-perlite mixes due to the increased aeration.
  • Perlite is so much lighter than soil (it only weighs between 5 and 8 pounds per cubic foot) that it's very useful in gardening spaces where weight may be a critical factor, such as rooftop gardens.