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Cultivation Soil - Top 10 Tips for Selecting Growing Medium in 2021

Cultivating Soil Cannabis Education 2021 - Top 10 Tips for Selecting Growing Medium

Written by - Simon Hawk - 11.2.2020

Introduction to Selecting Soil for Cultivating Cannabis I have grown cannabis personally in a number of different soils in all types of locations from indoor basement grows to giant outdoor fields. Each time the growers used different soil to be honest. There are so many options these days that it is important to understand what you are planting into before you start your operation. Many farms will stay with the same type of soil even if they are having problems, smart growers know that there are options.

1. Selecting soil based on plant - What do Cannabis Plants need from soil?

The easiest way to select soil is based on what kind of plant you will be growing. Cannabis plants are similar to Tomoato plants genetically and both require sufficient amounts of the macro nutrients NPK. To grow large healthy cannabis plants the soil will need to contain other micro nutrients, beneficial fungi, microbes and sugars to support large bud growth. THE MACRONUTRIENTS NEEDED FOR BASIC CANNABIS CULTIVATION ARE AS FOLLOWS :


Nitrogen is a key macronutrient in plants. Widely considered the single most important component for plant growth. Nitrogen forms part of the chlorophyll molecule—the chemical that gives plants their green colour. The molecule is created within the chloroplasts of plant cells and is needed to absorb sunlight. Without chlorophyll, plants wouldn't last very long. Once sunlight is absorbed, plants use this energy in the creation of vital sugars.

Nitrogen is also a major component of plant protoplasm. Protoplasm is the living content of a plant cell that is held in place by a plasma membrane. This area of the plant is full of key nutrients like amino acids, sugars, water, lipids, and nucleic acids.


As one of three core macronutrients, phosphorus is essential to healthy plant growth. The mineral is required for normal plant maturity, and plays a critical role during photosynthesis, respiration, and energy storage. Phosphorus is a vital component of ATP, the cellular currency of energy. ATP is the result of photosynthesis, and plants use the molecule for many chemical reactions. Phosphorus plays a role in plants at the genetic level. It helps to form DNA (molecules that contain the genetic code of a plant) and RNA (molecules that copy and transfer the code within DNA).


Potassium is the final primary macronutrient in our lineup. This mineral fulfils numerous key physiological functions. Potassium helps regulate CO₂ uptake in plants by opening and closing the stomata—small holes located on stems and leaves. By enabling these pore-like structures to open, potassium causes carbon dioxide to enter and oxygen to leave. Because plants use CO₂ during photosynthesis, potassium is also vital in this energy-forming process. The mineral is also used in plants to activate enzymes that are important in the production of ATP.


Calcium plays an important structural role in plants. The mineral contributes to the integrity of cell walls and membranes. Calcium also plays the role of an intracellular messenger, enabling plants to respond to developmental cues and environmental challenges. Because calcium is a structural component, the lack of it can become very apparent. When plants are deficient in calcium, old leaves begin to die off and plants take longer to flower. New tissue growth, such as root tips and young leaves, will also exhibit distorted growth.


Magnesium is one of the most important nutrients when it comes to photosynthesis. The metallic element is the powerhouse behind the process and exists in the heart of the chlorophyll molecule. Without it, plants would not be able to capture light energy.

Plants use magnesium for more than energy processing, such as to metabolise sugars and stabilise cell membranes.


Sulphur is another important structural mineral in plant physiology. It assists in the formation of proteins—molecules used to form hormones, enzymes, membrane channels, and pumps.



Alongside calcium, boron is a vital structural component of cell walls. Boron is also directly involved in plant growth as it's essential for cell division. The nutrient is crucial during reproduction, especially during flowering.


Cannabis plants require small yet optimal amounts of chlorine to remain healthy. The nutrient helps keep their leaves firm and strong. Chlorine also assists in photosynthesis and plays a part in the opening and closing of stomata.


Copper plays the role of an activator within cannabis plants. It activates key enzymes that catalyse and speed up chemical reactions. Some of these enzymes are involved in the synthesis of lignin—a structural material that comprises the support tissues of vascular plants.


Without adequate levels of iron, plants turn from a luscious green to a sickly yellow. This is because the nutrient is involved in the production of chlorophyll, which gives plants their delightful green colour. Plants also need iron to form enzymes, produce energy, and reduce nitrate and sulfate levels.


Manganese contributes to essential survival processes and also helps to fight off disease. It's intimately involved in photosynthesis, respiration, and nitrogen assimilation. The nutrient is also required during root cell elongation and helps to protect roots against pathogens.


Plants only need molybdenum in super small quantities. However, its role should not be underestimated. Without molybdenum, plants would have a hard time making proteins. The nutrient forms part of two enzymes that convert nitrate into nitrite, and nitrite into ammonia to synthesise amino acids. Molybdenum is also used in the conversion of inorganic phosphorus into organic forms.


If you want your cannabis plants to exhibit healthy growth and optimal size, you'll need to meet their zinc demands. Fortunately, plants don't require much zinc at all. The little they do need is used to build enzymes, proteins, and growth hormones. Zinc is also crucial in internode elongation.

2. Selecting soil based on availability

Not everyone lives in a metro area or a state that allows for hydroponic/grow stores to operate. In cases where commercial supplies are limited it is best to select from the available options. There are 2 brands that are regularly found at Garden store or Hardware stores that are suitable for growth are as follows. Promix - Inorganic/Soiless medium - Ideal for Indoor

FoxFarm - Organics/Living Soil - Ideal for Outdoor If none of these are available locally you can simply create your own mix by combining the following materials bought individually: Peat moss, Dolomite lime, Perlite, Epsom Salt, Compost, Eart Worm Castings

3. Selecting soil based on environment

The ideal environment exists and it is very much dependant on the microclimate where the location is. If the cultivation is taking place indoors or outdoors. For Indoor grows the majority of growers prefer soiless mediums that they can feed nutrients directly into.

If you are growing Indoors and can order topgrade soil for your cultivation the following soil is recommended :

Canna -

Buildasoil -

If you are growing outdoors and have the means to order high quality organic living soil the following brands are highly recommended : Roots Organic -

Deep Dive into Theory

4. Organic Living Soil produces higher terpenes

When growing organically and planting directly into the ground or using living soil we are seeing larger plants with more terpenes. The terpenes are now proving to be the dominant factor in the effects of Sativa or Indica. The fragrant lemon smell is provided by limonene the terpene that effects us with a sativa feeling vs the calming scent of lavender which comes from the terpene linalool providing an indica effects.

The research suggests that soil with added nutrients increase terpene production rates. Organic Living soil rich in natural fertilizers will have plenty of nutrients :

When soil is lacking life it can be boosted by applying solutions like LABS ( : Lactic Acid Bacteria Serum )

5. Coco Coir is a much easier growing medium to control

With indoor grows in sterile environments it is common to find only coconut husk/fiber based grow mediums as they are less susceptible to mold or fungus. Considering the organic nature of the medium, this is a safe bet for some grows seeking a low maintenance medium. The benefits of coco cubes for growers with larger operations is the ability to stack the blocks as the plant grows. Seedlings started in coco cubes can be placed on top of coco-bricks and stacked again ontop of a coco-bag with minimal labor required. Reducing the amount of organic material in the medium effectively mitigates alot of risk from overwatering and pests. Without the organic matter to decompose or attracts bugs, the medium becomes easier to control.

6. Soiless mediums require more inputs When the soil used to grow cannabis lacks nutrients like with Promix or Coco Coir additional feeding is required to ensure the plant receives the proper nutrients for growth throughout the life cycle. Since soiless mediums contain little to no macro or micro nutrients, compost teas and liquid or powdered fertilizers are applied to maintain a healthy plant. This requires a consistent feeding scheduled paired with a cocktail or ingredients to increase yield. Soiless mediums can still be fed organic nutrients for a superior flower.

Real World Application

7. Growing outside in native soil

Growers with access to land can plant directly into the soil surrounding their home if the state permits it. Native Soil is simple the soil that already exists in a location and is not brought in from another area. Building large containers or digging beds to plant cannabis in has been done in california for generations with great success. If crops have never been grown in the soil near you, a soil sample can be tested to analyze what macro and micronutrients are missing. Amending soil with organic fertilizers, compost and cover crops can prepare the area for a large harvest.

When selecting native soil to grow in it is important to understand that sandy/clay soil is not ideal for cannabis. Rich dark organic matter filled loose soil is ideal, if you can grip it in your fist and it retains its shape there will be enough clay to retain water during dry periods. Select a spot that is semi shaded, yet receives full sun for a minimum of 12 hours for flowering cannabis plants.

8. Ordering Soil online

Soil can be ordered online for small operations or purchased in bulk for large operations. For small home grows Order here :

For Medium sized licensed grows order here :

For Large size commercial operations order here :

When ordering supplies for greenhouses to amend soil or purchase equipment use

9. Visitng a nearby Garden Store

You can easily pickup soil locally by visiting a nursery that is near to your location. Reducing shipping costs and supporting local businesses is great. When you order online or in bulk you get wholesale pricing.

Many tree farms and agriculture operations sell local soil and compost as well

Use google maps to search for "Garden Store" or "Nursery"

Summary and Cheatcodes

10. Choose soil that works for you with these 3 factors

  1. Experience - Depending on how skilled of a grower you are it can be beneficial to start with an easy medium like coco which is less likely to be overwatered and is more forgiving with mistakes.

  1. Location - Depending on where your grow is located , indoor or outdoor, you will want to choose a medium that is ideal for the climate. Outdoor growers normally prefer living soil with organic content so they do not need to feed as many nutrients and clay in the soil retains more water. Indoor growers usually select soiless medium with less organic content to reduce the risk of pests, bacteria and excessive fungi.

  1. Budget - Depending on the amount of capital available for purchasing soil it is important to select a medium that fits your budget. Cannabis specific soil brands that feature the ideal nutrients, soil amendments and correct ratios of perlite are often the most expense.


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