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Should You Add Perlite to Your Soil?


by Nebula Haze

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.

Closeup of horticultural perlite - a perfect soil amendment for growing marijuana!

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

Example of good cannabis soil - Ocean Forest soil by Fox Farm

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!

Coco coir and perlite potting mix - ready for growing
 

Perlite for Growing Marijuana

  • Buy perlite on Amazon.com!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.

Horticultural perlite is a great amendment for growing weed!
 

How Much Perlite to Add?

Example of mixing up perlite into pure coco coir - this makes a great cannabis potting mix!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. 

Example of horticultural perlite - an amazing soil amendment for growing weed!

Get a Bag of Perlite on Amazon

Buy a bag of perlite on Amazon.com

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

Example of obsidian from Panum Crater

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

Example of the perlite beneficiation process - this turns volcanic rock into expanded pebbles
Amazing picture from 911metalugist.com

 


 

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