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
Soil in Containers Should Be a Good Mix
Garden soil doesn’t offer enough air, water, or nutrients to container-grown plants. Fortunately, it’s easy to amend.
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I work hard to ensure that the soil in my garden is the best I can give my plants, and they reward me with robust health. Yet that same good soil if transferred to a container would cause the plants in it to languish. That’s because garden soil doesn’t offer enough air, water, or nutrients to a plant growing in a container. Potting soils are specifically formulated to overcome these limitations.
Potting soil needs to drain well but still hold moisture
One of the most important things a potting soil needs to do is provide roots access to air by letting water drain away from them. In the ground, the soil is usually deep enough to let excess water drain beyond root zones. In pots, however, water tends to accumulate at the bottom, despite drainage holes. The smaller the pore spaces of the soil in the pot, the higher that water layer will reach. Larger pores, formed by adding mineral aggregates to potting soils, readily admit water into the soil, then carry it through the medium and out the bottom. Then, all those large, empty spaces can fill with air.
Perlite, vermiculite, calcined clay (kitty litter), and sand are the mineral aggregates most commonly used in potting soils. Perlite and vermiculite are lightweight volcanic rocks naturally filled with air. I prefer perlite over the others because it does not decompose with time nor lose its aerating ability if the potting mix is compressed. Vermiculite is a valuable additive because it prevents some nutrients from leaching away, and it even provides a bit of potassium and magnesium.
A potting mix also must have ingredients that help it retain moisture. This is where organic materials—usually peat moss, sphagnum moss, or coir—come in. They cling to some of the water that the aggregates are helping to drain. Organic materials also hold on to nutrients that might otherwise wash away.
In addition to peat moss, vermiculite, and perlite, commercial mixes often contain sawdust or various grades of shredded bark. Lime may be added to help balance the acidity of the peat moss, and a small dose of fertilizer can often make up for the lack of nutrients.
Adding compost or garden soil can be beneficial
Most gardeners make potting soil by combining perlite or vemiculite with peat or sphagnum moss. Two other organic materials that you could add to your potting mix are leaf mold and compost, which offer a wide spectrum of nutrients.
Adding some garden soil to a homemade potting mix contributes bulk while buffering against pH changes and nutrient deficiencies. The reason that garden soil is rarely added to commercial mixes is because of the difficulty in obtaining a steady supply that is consistent in quality and free of toxins such as herbicide residues.
Customize your mix to suit your plants
Soilless potting mixes are relatively free of living organisms, but mixes made with soil or compost are not. Some gardeners talk about “sterilizing” their potting mixes by baking them in the oven to rid the soil of harmful organisms, limiting the hazards of damping-off and other diseases. What I hope they mean is that they “pasteurize” their mixes. Heating homemade potting mixes to sterilizing temperatures wipes out all living things, beneficial and detrimental, leaving a clean slate for possible invasion of pathogens and causing nutritional problems such as ammonia toxicity. Pasteurization, which occurs at lower temperatures, kills only a fraction of the organisms. The best way to pasteurize your soil is to put it in a baking pan with a potato embedded in the soil. Bake it at 350°F for about 45 minutes. When the potato is cooked, the potting mix is ready.
I don’t pasteurize my potting mix. I rely, instead, on healthy container-gardening practices such as timely watering, good air circulation, and adequate light to avoid disease problems. Beneficial microorganisms in compost and garden soil also help fend off pests.
Lee’s recipe for homemade potting soil
I’ve found that making my own potting soil produces better results than commercial mixes and eliminates the need to monitor my containers’ nutrient and pH levels. With plenty of good soil in my backyard, I have no trouble making this traditional potting medium. It features a mixed bag of ingredients, but I figure that plants, like humans, benefit from a varied diet. This mix can support plants for a year or two without additional fertilization.
Mix 2 gallons each of:
* peat moss
* garden soil
with 1/2 cup each of:
* dolomitic limestone
* soybean meal
* rock phosphate
* kelp powder
I place a 1/2-inch mesh screen over my garden cart and sift the peat moss, compost, and garden soil to remove any large particles. I then add the remaining ingredients and turn the materials over repeatedly with a shovel, adding water if the mix seems dry. After a few incantations, the stuff is ready to work its magic on everything from my tomato seedlings to my weeping fig.
Make your own soilless mix
Years ago, Cornell University scientists came up with a formula for a soilless potting mix, which forms the basis for many commercial potting mixes on the market today. By following this recipe, you can easily replicate what is sold in bags at the garden center.
* 1 bushel peat moss
* 1 bushel perlite or vermiculite
* 1/2 pound dolomitic limestone
* 1 pound 5-10-5 fertilizer
* 1 1/2 ounces 20% superphosphate fertilizer
Mix the ingredients thoroughly. The mix is initially hard to wet, so moisten it as you stir it. This saves the trouble of doing so each time you remove some for use.
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Garden soil doesn't offer enough air, water, or nutrients to container-grown plants. Fortunately, it's easy to amend.