Peat Moss is the Perfect Growing Medium for Cannabis

Francis Cassidy March 3, 2020 0 comments

Although often overlooked, peat moss is one of the most effective mediums for growing cannabis.

A peat moss medium requires a lot less work to set up than a hydroponic or aquaponic setup. With some know-how and little preparatory work, a peat moss medium may bring yields to the next level.

What is Peat Moss?

Also known as sphagnum moss, peat moss is part of a family of almost four hundred separate moss species. When used in soil, peat moss consists of the partially decomposed remains of several types of moss.

A study funded by the Environmental Protection Agency (2015), cited the antibacterial and other preservative properties of sphagnum as a valuable inclusion in growing mediums.

Advantages of Peat Moss for Growing Cannabis

Peat offers several benefits to the cannabis grower. Firstly, it retains up to twenty times its weight in water, something that helps hydrate plants over a longer period of time. It also contains some important micronutrients, and the medium is free from weeds, pests, and pathogens.

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When correctly prepared, peat moss encourages the proliferation of a healthy community of microorganisms. And the key to optimal growth is a diverse community of fungi and bacteria around the root zone. Such organisms break down organic matter and help make nutrients more readily available to the roots.

peat moss with cannabis growing out of it

Preparing Peat Moss

In its natural state, peat moss does not absorb water well. To prepare the peat moss, spread it out over a plastic covering or another contained surface. Moisten it thoroughly and allow it to dry in the sun for two to three weeks. Throughout this time, the peat becomes more absorbent, and important micronutrients also begin to proliferate in the medium.

Do not let the medium dry out or become overly moist. Also, water it in hot weather, and if it rains, do not allow the accumulated water to sit. Once complete, mix the peat with identical quantities of potting soil. Adding perlite at this time will also help with aeration for optimal root development. To complete the process, simply add some quality compost and mix everything thoroughly.

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Transplanting Into Peat Moss

When transplanting, the size of the pot is of critical importance. As a general rule of thumb, a cannabis plant will require one gallon of medium for every one foot in height above the ground.

Pot size selection is crucial because it affects root development. As roots grow, they spread outwards in search of water. And as the soil dries from the inside out, the roots grow outward uniformly to the edge of the pot. This is how roots make efficient use of available soil.

Why Pot Size is Critical

An imbalance between the root mass and medium occurs when a small plant is placed in a large pot saturated with water. It takes much longer for the soil to dry out as there is not enough root mass to consume the water. This actually stunts plant growth, and the plant may even be deprived of oxygen and exhibit signs of nutrient deficiency.

Some people try and circumvent these issues by only watering in a small circle around the plant. But without knowing exactly how much water is in the pot, most cultivators only end up making additional problems for themselves.

By using an appropriate size pot, the root zone will quickly make use of the available water, something that’s crucial to healthy plant growth. Depending on the chemovar, a healthy plant in the right size pot may grow up to one foot per week under ideal conditions. A healthy root zone means a fast-growing healthy plant and, ultimately, a maximized yield.

peat moss bog

Watering a Peat Medium

It is important to resist the temptation not to over-water a moss medium. If the medium is still wet, do not add additional water. By covering the roots in water, the oxygen content of the root zone will drop and the roots will drown.

After initial transplanting, it may take some time for the medium to dry up, perhaps up to four days in cases. When it comes to water, reverse osmosis water will greatly increase consumption.

Peat Moss Mediums Versus Coco Coir

Coco coir is another type of soil medium popular among cannabis cultivators. Like peat moss, it offers several advantages. Some of the benefits of coco coir include the fact that it’s cheaper than peat moss, and its pH comes in at 6 – 6.7, the ideal range for cannabis. Like peat, it’s also highly effective at retaining water, retaining between eight to thirty times its weight. It is also free from pests, pathogens, and seeds.

On the downside, coco coir has high quantities of salt. Therefore, it requires thorough washing before use. Unlike peat moss, coco coir does not contain much in the way of microorganisms, or the trace elements all so important for top quality cannabis buds. Both mediums are effective for cannabis cultivation, and the choice typically comes down to grower preference and experience.


Taskila, Sanna & Särkelä, Riikka & Tanskanen, Juha. (2015). Valuable applications for peat moss. Biomass Conversion and Biorefinery. 6. 10.1007/s13399-015-0169-3.
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Francis Cassidy
Francis Cassidy is a freelance writer who writes on a variety of topics. With a particular focus on the cannabis industry, he aims to help ensure the smooth reintegration of cannabis back into global culture. When not writing, he's to be found exploring his new base in British Columbia, Canada. You can follow his other works including his photography on his blog

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