best perlite for cannabis

Should You Add Perlite to Your Soil?

A common soil amendment for cannabis plant is a substance called perlite. This can be added to soil or coco coir to improve its air-holding capabilities and increase overall drainage ability. It’s not a requirement for cannabis growth, but it’s so useful that nearly all recommended potting mixes contain at least a little perlite.

Horticultural Perlite – A great amendment for soil or coco when growing cannabis. Perlite looks like little white rocks, but the pieces feel oddly light and airy, almost like popcorn.

Nearly All High-Quality Cannabis Soil Mixes Contain At Least a Little Perlite

A 50/50 Potting Mix of Coco & Perlite – Perlite provides more oxygen to the roots, resulting in faster growth. It also prevents nutrient buildup. This perfectly complements the ability of coco coir to hold onto a ton of water. Learn how to mix up your own coco/perlite mix!

Perlite for Growing Marijuana

Perlite is one of the most common soil amendments. It is highly recommended for any cannabis soil or coco mix that doesn’t contain some already.

Perlite appears as very light, airy white “rocks” that feel almost like popcorn.

Adding perlite increases the overall drainage ability in a potting mix, helping prevent overwatering.

Perlite helps prevent nutrient buildup which makes it a good choice when growers are giving nutrients and supplements in the water

More oxygen in your soil or coco results in faster growth. Roots love oxygen! Perlite increases the amount of oxygen available to the plant roots because it does not retain water. As a result, air pockets form around the perlite even when the growing medium is wet.

How Much Perlite to Add?

It’s recommended to add perlite so it makes up around 10-50% of the total volume of potting mix.

Add 10-20% perlite if you want better water retention and don’t plan on using a lot of extra nutrients. This is because a lot of extra perlite can cause the nutrients leach out faster from the soil as water drains through easily.

Add 30-50% perlite if you plan to use a lot of added nutrients or supplements and are looking to get the fastest growth from your plants.

I have used many types of perlite including Epsoma, Black Gold, Shultz and even Miracle-Gro perlite. Any 8-quart bag of perlite will work. Perlite can often be found in garden stores or the garden section of home improvement stores like Home Depot and Lowes. I normally advise against all things Miracle-Gro, but their 8-quart bag of perlite is okay if you can’t find anything else.

What is Perlite?

The light, almost fluffy perlite we use for gardening does not occur naturally. It is actually manufactured from expanded volcanic rock.

It all starts with lava (like the kind from a volcano!) which cools and sometimes turns into obsidian, a shiny black glass that can be mined from the ground.

Example of obsidian, which is formed out of lava

As centuries pass, obsidian absorbs water from the air. This hydrated obsidian is mined and crushed into small pieces. The pieces are then expanded by adding huge amounts of heat. Due to the high amount of water contained inside, the heat causes the perlite pieces to pop like popcorn. That is why perlite feels so light – it is made up mostly of air!

Production of Horticultural Perlite

Should You Add Perlite to Your Soil? A common soil amendment for cannabis plant is a substance called perlite . This can be added to soil or coco coir to improve its air-holding capabilities and

What Is Perlite And How Is It Used To Grow Cannabis?

Published : Jan 15, 2019
Categories : Cannabis cultivation

Perlite is a common addition to potting soils, being highly favoured for its excellent drainage capabilities. Thankfully, cannabis can also benefit from this highly versatile growing medium. Perlite allows growers to mitigate some of the risks when overwatering, and helps maintain better control over pH levels. Keep reading to find out more.

Soil is often favoured for its ability to retain natural organisms and moisture. However, these benefits can quickly overwhelm plants and lead to a string of problems. This is where perlite steps in to counterbalance some of the negative qualities of soil. In typical applications, perlite is mixed with soil to create a growing medium that has improved drainage, but still retains the soil’s natural attributes. The result is a healthier, stronger cannabis plant that can produce better yields.

We’ve alluded to how versatile perlite is, but if you’ve never used it before, you may be wondering, what actually is it? Perlite is an inert substance (pH 7.0) that starts life as obsidian, a type of volcanic rock. Over time, the rock will have absorbed moisture from its surrounding environment and once mined, is crushed into smaller pieces. When the crushed obsidian is exposed to extreme temperatures (850–900°C), the moisture inside evaporates, forcing the rock to expand rapidly. The result is a popcorn-like substance that is incredibly light, with a brilliant white appearance.

Having been “popped”, perlite is now ready for commercial distribution. The growing medium can be found in garden centres the world over, appreciated for its airy structure and improved drainage qualities. When buying perlite, three grades are available: fine, medium, and coarse. For growing cannabis, “fine” perlite is the preferred option.

While it is possible to grow cannabis using a growing medium consisting entirely of perlite, this approach is most commonly used in hydroponics and requires advanced growing knowledge to get the best results. In the majority of scenarios, perlite will be mixed with soil or coco coir to create a balanced medium for growing cannabis.

For both soil and coco coir, you can add between 10–50% by volume of perlite. If you are planning a modest nutrient cycle, aim to use between 10–20%. This volume of perlite provides a middle-ground between moisture retention and runoff. If, however, you intend to use a lot of added nutrients or supplements, a 30–50% perlite mix can negate the risk of nutrient lockout from the plant being overloaded. At this level of concentration, the leaching of nutrients will be high because of the increased drainage and subsequent water runoff.

It isn’t just the improved drainage that makes perlite an advantageous medium for growing cannabis. Below are several reasons why you should consider adding it to your next indoor grow:

• Increased oxygen levels form because of the air pockets created by perlite. Roots thrive on oxygen, so expect improved rates of growth.

• Being inert, perlite will not upset nutrient concentrations.

• Ideal for clones, as the lightweight structure of perlite means roots can penetrate easily.

• The decreased weight means handling potted cannabis plants is much more comfortable. The benefits stack up when you are cultivating multiple plants.


• The increased drainage can magnify the frequency of watering routines, so you will need to keep a close eye on plants.

• Leaching of nutrients means careful control of pH is needed to maintain an optimal environment. You will need to pH test runoff every time you water.

• If you need to leave a plant for an extended period, it will not cope well, as it is more reliant on your input.

• For hydroponic systems, perlite needs to be washed first. There is a fine dust that covers the substance, which, if left, can clog systems.

Many of the disadvantages of using perlite can be easily mitigated. This makes the benefits significantly more accessible, and in nearly all scenarios, perlite is an essential addition to growing cannabis. It can be used with soil and coco coir, although it’s worth noting that the partnership between perlite and coco is particularly unique.

Coco coir does an excellent job of retaining moisture, staying oxygenated, and being less vulnerable to pests than soil. In combination with perlite, you can create the perfect balance between drainage and water retention. As long as you have planned your nutrient routine, plants can really excel with a 50/50 coco-perlite medium. To find out more of the benefits associated with growing in coco coir click here.

Now that we know what perlite is, how it’s made, and how beneficial it can be for potted cannabis, there seems little reason not to use it in your next grow. With the ability to improve yields and promote healthy growth, perlite could be your new best friend.

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Perlite can make growing potted cannabis significantly easier. Click the link for everything you need to know about the pros and cons of using perlite.