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Cannabis Nutrients & pH Explained

When adding nutrients and fertilizers to your cannabis plants, it’s vital to fully understand the differences between the various bottles and numbers, as most nutrients will be specific to a growing stage. For more information about the growing stages of the cannabis plant, check out our other available blog posts.


Macronutrients refer to the nutrients the cannabis plant needs in higher quantities than any micronutrient. The three primary macronutrients are nitrogen, phosphorus, and potassium. Other macronutrients include carbon, hydrogen, and oxygen, all of which the plant obtains self-sufficiently.

  • Nitrogen (N) is responsible for vigorous, leafy growth and rich green colours in lawn grass and other plants. Without enough nitrogen, growth will slow or stall, and plants will turn pale in colour. With too much nitrogen, flowering and fruit-bearing plants will put all their effort into leafy growth and sacrifice their flowers and fruit.
  • Phosphorus (P) focuses the plant energy into sturdy root development and flowers, fruits and seeds while helping plants use other nutrients efficiently. A shortage of phosphorus would leave the roots weak and the fruit and flowers lacking.
  • Potassium (K) enhances the plant’s overall growth. It will help regulate growth and keeps plants healthy and well-balanced. This affects the plant’s well-being, including cold and drought tolerance with disease and pest resistance.
  • Carbon Dioxide (CO2) is converted by the plant into energy and is required for photosynthesis.
  • Hydrogen (H) is another building block for the cannabis plant during growth. Plants use hydrogen ions to drive the electron transport chain during photosynthesis.
  • Oxygen (O) is needed as the roots don’t have access to light for photosynthesis. Oxygen also helps the plant release energy from stored glucose.

NPK Ratios

Those three primary nutrients make up the NPK ratio displayed on nutrient labels and are always in that order.

The demand for each nutrient differs with the growing cycles. Plants amid their growth cycle will need more nitrogen with less phosphorus and potassium, and flowering plants will need significantly less nitrogen and abundantly more phosphorus and potassium.

Essential Secondary Macronutrients

Some sources don’t separate the secondary nutrients and lump them in with the macronutrients since they aren’t needed in large quantities. They must be in significantly higher amounts than the micronutrients, which will be covered later.

The essential secondary nutrients are magnesium, calcium, and sulphur. These nutrients perform a wide range of critical functions for proper cannabis development, are often necessary components or complementary to other nutrients and purposes and are needed for plant and root growth.

  • Magnesium (Mg) is a critical component of chlorophyll, the powerhouse behind photosynthesis. Magnesium is also necessary for cell division, protein synthesis, and enzyme activation.
  • Calcium (Ca) assists in transporting other nutrients and aids in their absorption. It’s also vital for the structural integrity of the plant.
  • Sulphur (S) aids in the transport of chlorophyll and assists with plant metabolism, protein production and transpiration.

The lesser amount of required secondary nutrients to aid in the proper growth and development of healthy cannabis should not be mistaken as being less vital than the macronutrients. The same can be said regarding the small amount needed for micronutrients.

Essential Micronutrients

These essential micronutrients represent elements and minerals that aren’t as abundantly available on Earth and are only needed in minimal amounts by the cannabis plant.

No matter what source of information, boron, manganese, zinc, copper, iron, and molybdenum are always included in the list of micronutrients. Like the other nutrients, all micronutrients have a unique function or assist in the purposes and processes of the other nutrients.

  • Boron (B) helps with the development and growth of root tips. It also aids plants’ calcium absorption and transports sugars within the plant.
  • Manganese (Mn) is a vital component of chlorophyll production and photosynthesis. It also assists with enzyme interactions.
  • Zinc (Zn) aids in stem, leaf, and branch development. The more mature a plant is, the more zinc is present and needed.
  • Copper (Cu) assists in the development of plant proteins and helps with the strengthening of stems and branches.
  • Iron (Fe) is essential for chlorophyll production. Iron deficiencies often present as a yellowing of the leaves between the leaf’s veins.
  • Molybdenum (Mo) helps the plant process nitrogen.

Soil pH Levels

Almost, if not more, as important as the nutrients are to the overall health of the plant is the soil or growing medium used. The pH, which is the acidity or alkalinity level of the growing medium, can make a vast difference to the welfare of the plant.

Soils or other media with a pH of less than 7.0 are acidic; soils or other media with a pH greater than 7.0 are alkaline.

The pH is important because all the required nutrients could be available to the plant but locked out or unavailable if the pH is too high or too low. The ideal pH range for cannabis soil is 6.0 to 7.0, depending on the growing medium used.

Nutrient Availability Chart: ideal pH levels for nutrient absorption.

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