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Growing Media Best Practices for Cannabis

In the first of a series of articles from international agritech company Premier Tech, we delve into which growing mediums will enable cannabis cultivators to achieve the best yields. 

Growing medium is generally made with a base of organic components. In North America, these consist of Canadian Sphagnum Peat Moss, an aggregate such as perlite, and may include additional components such as coir and/or wood fiber. Limestone is incorporated to adjust the pH to the correct range for plant growth; wetting agent helps provide for fast water absorption, distribution and movement throughout the container; and a starter nutrient charge that is designed to help with initial plant growth.

A good growing medium is designed to achieve specific chemical and physical characteristics for cannabis plants. It serves as a water reservoir, nutrient holding and exchange site, it provides an anchor and support for plants, and it is a gaseous exchange system for the plants roots.

Select a growing medium that has a good balance between water holding capacity and air porosity for a healthy root system. Use the appropriate growing media type for your crop needs and growing environment. View the table below for an overview of the main types of growing media:

Main type of growing media Water holding capacity Air porosity
General purpose Moderate Moderate
High porosity Low High
Peat-coir High High
Coco High High

The appropriate growing media matched to your growing environment and crop needs will greatly assist in the growth of a healthy, high yielding crop.

Water Quality and Watering Practices

Water can contain high levels of sodium, chloride, fluoride, boron or other elements that can be detrimental to crops.  Water source should be tested annually to determine the alkalinity and individual nutrient levels to prevent unforeseen issues that may arise due to water quality.

Alkalinity is the measure of the bicarbonates and carbonates in the water. Knowing the alkalinity will help match the fertilizer to the water quality.



If the irrigation water used has an alkalinity above 250 ppm CaCO3, it can cause the medium pH to rise out of the desirable range for plant growth.  Incorporate a nutritional program that uses fertilizers with high “potential acidity” or inject acid into the irrigation water to minimize the climbing pH of the growing medium.

Irrigation practices can also affect crop quality.  Overwatering can be as detrimental as underwatering to crop health and quality.  Improper irrigation practice can provoke stretching, root disease, algae, shore flies and fungus gnats and plant height.  Learn to recognize when to irrigate your crop.  There are several methods used: observation of the surface color, measuring the container weight, finger stick, and looking directly at the root ball.

Plant Nutrition

A starter nutrient charge helps plants acclimate and get established.  Depending on the manufacturer and the product’s intended use, the E.C. can range from 0.5 to 2.5 mmhos/cm.  It generally lasts about 7 to 10 days once in use.  After that, the nutritional program for the crop should be started and maintained throughout the crop cycle.

Beneficial microorganisms

Biological beneficial microorganisms, such as bacteria or fungi, are used to enhance plant growth, reduce plant pathogens that can cause plant root disease and/or reduce insect populations.

Since most growing media are composed of materials that are poor in microorganism’s content and diversity, adding biological active ingredients, such as mycorrhizae and Bacillus, an earlier and more efficient use of water and nutrients will help the plant reach optimum yield.

Rhizophagus irregularis (formerly known as Glomus Intraradices) is an endomycorrhizae which colonizes most herbaceous plants including cannabis. It is a natural occurring beneficial fungi that forms a symbiotic relationship with the plant.  Mycorrhizae colonizes the plants roots to form a network of filaments that penetrate the root and grow outward throughout the medium to allow the plant access to more nutrients and water, than the roots alone would have access to. This fungi-plant alliance stimulates plant growth and increase yield by increasing root mass, flower production, plant size and tolerance to stresses throughout the plant life cycle.


Bacillus used in PRO-MIX® is a natural occurring gram-positive bacteria that colonizes the root. It forms a biofilm around the root system and secretes biostimulant molecules (auxins) that stimulate root growth to favor the absorption of nutrients and water. Bacillus pumilus is fully compatible with mycorrhizae and continues to grow with the root system and the mycorrhizae for season long protection.

The addition of active ingredients such as mycorrhizae and Bacillus can help the grower save money, preventively protect roots for pathogens and reduce incidence of root disease, reduces the exposure to chemical pesticides, is another option for their IPM toolbox and can increase their Return on Investment (ROI).

In summary, the best practices for growing cannabis are to consider the growing media best suited to the cell/pot size and the growing environment. Start your nutritional program with a water test to know your water quality so that you can select the appropriate fertilizers to help neutralize the effects of water alkalinity on media pH and meet the nutritional needs of your crop. And, last but not least, use active ingredients such as mycorrhizae and Bacillus to improve you crops performance and increase your yields.

Premier Tech has a wide range of products, services, brands and technologies allowing to increase crop yields, bring beautiful gardens to life, automate the handling and packaging operations of many manufacturing facilities, treat and recycle water, support companies in their digital transformation and offer bio-ingredients for the well-being of humans and animals.

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