Perlite or Vermiculite – What’s the Difference?

Perlite or Vermiculite – What’s the Difference?

Whether you are an avid gardener, or just starting off, you’ve probably asked yourself: “Perlite or Vermiculite – what’s the difference, and which one should I use?”

To be sure, they do have similar characteristics and serve similar purposes: both perlite and vermiculite are inorganic products, both are relatively sterile, and both are often used as soil additives. Both perlite and vermiculite have water retention properties and both help to aerate the soil.

However, there are notable differences between the two, and depending on the type of plants, nature of the soil, and the purpose for which you may using these products, will determine which one is better suited for your needs.

Perlite or Vermiculite - what's the difference?

Perlite

Differences

Perlite is a porous pumice-like material that looks like white granules. Sometimes perlite is mistaken for tiny plastic foam balls when used in potting soil mixtures. It is actually an amorphous volcanic rock that is rich in silicon. When prepared to be used as a potting medium or soil additive, perlite is crushed and also heated to expand the particles. The microscopic bubbles in perlite granules absorb and hold water as well, but they also hold air.

Vermiculite

Vermiculite is a spongy material that is dark brown to golden brown in color. It is shaped like flakes when dry. It is an aluminum-iron-magnesium silicate that resembles mica in appearance. For use in horticultural applications, vermiculite is heated to expand the particles. This expansion enables it to absorb moisture when used as a potting medium or soil additive. Vermiculite can soak up 3 to 4 times its volume in water.

Which To Use

Though both products are used for aerating the soil, the fact that vermiculite holds moisture longer than perlite makes their usage different. Vermiculite retains more water and retains it for longer periods than perlite. Vermiculite provides slightly less aeration than perlite. For plants that thrive growing in a more-wet soil, vermiculite would do well as a potting soil additive. Since many foliage plants appreciate more water-retentive potting soil, they do well in a vermiculite-added potting soil. Also, simply because of its water retention/nutrient retention, vermiculite makes a good seed-starter medium.

While vermiculite would be a better choice for starting seeds, perlite would be a better choice when rooting cuttings. Cuttings would tend to rot more easily in vermiculite. For plants that need a quickly draining soil, a soil that does not retain much moisture, a soil that is extremely well aerated, and a soil that could have a higher pH, perlite would be the best additive.

In summary, although vermiculite and perlite have some similar properties, they are not the same. When plants need more water-retentive soil or for seed-starting, use vermiculite. For plants that prefer quick-drying soil or for starting cuttings, use perlite.

To see a complete selection of our organic growing mediums and fertilizers, click here.

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