Perlite

Perlite is the small white, pumice-like grains that you will find in quite a few potting mixes currently available on the market. It is an expanded natural volcanic glass, produced in a similar way to clay pebbles, whereby the raw material is heated up to an extremely high temperature causing it to quickly expand, becoming a highly porous material filled with micro-pores of space, this means water can pass freely through it.

Primarily it is used to help improve the drainage and aeration of your growing substrate, meaning that you are much less likely to run into problems associated with over-watering than when you use a substrate without perlite added into it. It is particularly useful to add into your growing media when you are using systems such as Autopots, that are typically more saturated with water, to ensure they do not become waterlogged. 

By increasing the oxygen levels within your medium you will see greater nutrient uptake and improved root health. This increase in the health of your root zone allows them to be far more resistant to diseases. What's more is perlite is comprised primarily of silicon dioxide so you can see some of the plant boosting benefits of silicon just by adding it to your medium.

How To Use Perlite

Perlite has a number of uses which vary from grower to grower. It does not require any pre-treating before use. These are three popular methods of use:

Mixing directly with the growing media. This method is great for improving the overall aeration and performance of your medium. Add perlite to your choice of absorbent media (soil, rockwool, vermiculate or coco) at your chosen ratio before potting up and planting out. The more you add the more aerated it will become but remember this will the decrease the water holding properties so you will need to water more frequently. Common mixing ratios are usually 70/30, 60/40 or 50/50 (medium/perlite).

Adding a layer at the bottom of your pots. Much like clay pebbles perlite can be added to the bottom of your pot or growing container before filling the rest with your normal growing medium. This method works well if your plants are being either bottom-fed or are they are likely to be sitting in nutrient solution run-off for a period of time. It prevents the medium becoming oversaturated in these circumstances.

Using perlite as your growing medium. Yes, perlite can be used as a stand-alone hydroponic growing medium, it's inert and pH stable! Whilst more uncommon than others it can be used in pots with an irrigation system such as a dripper and treated as a hydroponic setup. You will need to water frequently, but if dialled in the results can be great due to the superb root growth you will get from the sheer amount of aeration of the medium.

Perlite is available in 10L and 100L bags.