Perlite as a Soil Amendment

Preparing a well-mixed potting medium is crucial in container gardening and nursery production. A potting mix can be soil-based or soilless. There are several amendments that you use to prepare a medium, it may include organic or inorganic materials. 

One inorganic material that is often used in preparing a potting medium is perlite.  Perlite is derived from volcanic rock. The material is heated to 1400-1800oF, causing it to expand and pop like popcorns. Perlite has a styrofoam texture and a bright, white color. 

Advantages of Using Perlite

There are various advantages of using perlite as a soil amendment. Following are positive reasons why perlite is a good choice for every gardener. 

Improves Drainage

When you mix perlite with soil and with other amendments, it creates spaces within the medium. The improved texture of the mix eases water flow lessening the chance of waterlogging. 

Increase Aeration

Perlite also increases soil aeration. When added in compact soil, the perlite materials occupy spaces which in turn create pores. These pores provide room for oxygen molecules to fill. 

Lightweight

The perlite materials will not make your potting medium heavy. It’s a good alternative to sand, which is quite heavy material. This is advantageous especially when you’re planting in containers. 

pH Neutral

Unlike other soil amendments, perlite won’t alter the pH of your potting medium once it’s added. This is a perfect choice if you want to maintain the existing pH of your potting mix. Know that the soil’s pH affects the availability of nutrients in the medium. More on soil info here.

Sterile

Because perlite is heated using a very high temperature, there’s this assurance that harmful organisms such as pathogens have been destroyed. Thus, it’s safe to use them as an amendment. You wouldn’t need to worry that the perlite will transfer diseases to your plant. 

Organic

Perlite is certified safe for use in organic gardening. The National Organic Standards Board (NOSB) of USDA permits the use of perlite by certified organic farmers. 

Chemically Inert

Perlite is a stable and non-reactive material. It’s safe to recycle this material without worrying about some environmental problems. 

Mixing Perlite in the Potting Medium 

From the left: Compost, Perlite, Vermiculite

You can utilize perlite by mixing it with other soil amendments. There are varying proportions you have to follow depending on what species of plant you’re going to grow. Here are samples you can follow:

Peat-Based (Soilless) Mixes

For Foliage Plants 

Mix 2 parts peat or coco coir; 1 part perlite; 1 part coarse sand

Soil-Based Mixes

For Cactus and Succulents

Mix 2 parts gardening soil; 1 part peat or coco coir; 1 part perlite; 1 part coarse sand

Mix 1/3 compost; 1/3 sieved & sanitised garden soil ; 1/3 perlite (as an alternative to sand)

Perlite is readily available and you can purchase them in varying portions such as Vitax Perlite 10 Litres and Vitax Perlite 20 Litres

Cautions in Using Perlite

Fluoride Toxicity 

Perlite contains fluoride which can potentially be toxic to plants if given in higher portions. Use moderate amounts of perlite when the plant you’re going to grow is fluoride sensitive. 

Health Issues

Be careful when handling perlite. It produces dust that may aggravate existing respiratory conditions. It’s a good idea to water it down before handling it to reduce dust inhalation. Always use eye and mouth protection.  

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