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ratio of perlite to potting soil

Recommended Ratio of Peat Moss to Perlite

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Peat moss and perlite are two of the most common ingredients in potting soil mixes. Peat moss, also known as sphagnum moss, is a form of partially decomposed organic matter harvested from acidic wetlands. Perlite is a volcanic mineral that expands when heated; perlite sold for horticultural purposes has already been processed into a light, grainy substance somewhat resembling small bits of popcorn.

Benefits of Peat Moss

The beneficial characteristics of peat moss make it an excellent addition to your potting soil mixture. Most importantly, peat moss can absorb large quantities of water. Without peat moss in your mix, it would be difficult to provide a steady water supply to the confined roots of your seedlings. Also, the fibrous nature of peat moss lends structure and physical stability to your potting soil; this is especially important if you intend to use a noncontainer growing medium such as soil blocks. Peat moss is free of weed seeds, harmful microorganisms and undesirable types of soil particles.

Benefits of Perlite

Perlite complements peat moss by providing proper drainage to your potting soil. Your growing medium must allow water and air to flow around your seedling roots. Perlite in the proper proportion adds beneficial porosity and lightness to your mix without significantly reducing the water-holding capacity. And unlike sand, which can also be used to ensure porosity, perlite is covered in tiny cavities that can hold small amounts of water.

The Proper Ratio

Do not be afraid to experiment with your potting soil recipe. Many different mixtures have proved successful over the years. In general, the volume of perlite should be equal to or less than the volume of peat moss: You need plenty of peat to keep your seedlings hydrated, but you need only enough perlite to ensure aeration and drainage. If your potting soil contains other ingredients that encourage good drainage (such as sand or vermiculite), you can reduce the quantity of perlite. The best place to start your experimentation is one of the recipes recommended by an authoritative grower or author.

Eliot Coleman’s Ratios

In his book “The New Organic Grower,” Eliot Coleman recommends a ratio, by volume, of 3 parts peat moss to 2 parts perlite. This recipe, however, is intended for soil blocks. In “Four-Season Harvest,” Coleman recommends a more general recipe that uses 3 parts peat moss to 1 part perlite.

Cornell’s Ratios

Researchers at Cornell University have developed and published several widely respected potting soil recipes. Some of these recipes, such as those for flowers, recommend 2 parts peat moss to 1 part perlite (by volume). The recipe for vegetable transplants uses 1 part peat moss to 1 part perlite.

Recommended Ratio of Peat Moss to Perlite. Peat moss and perlite are two of the most common ingredients in potting soil mixes. Peat moss, also known as sphagnum moss, is a form of partially decomposed organic matter harvested from acidic wetlands. Perlite is a volcanic mineral that expands when heated; perlite sold …

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