Growing cannabis yourself can be highly rewarding, but an overwhelming process at the start.  Should you grow indoor or outdoor?  How do you implement sustainable growing practices?  And how do you ensure that your plants are getting the right nutrients?  Here are some guidelines to help you get started. The quantity of nutrients you use on your cannabis is dependent on your plant’s growth stage.  That is particularly true for the most important macronutrients your cannabis needs to thrive: nitrogen (N), phosphorous (P), and potassium (K).

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Nitrogen, Phosphorous, and Potassium (NPK)

Nitrogen plays a critical role in photosynthesis as it facilitates the production of chlorophyll and amino acids.  A nitrogen deficiency is identifiable when the cannabis leaves begin to turn a pale yellow and eventually droop as the plant dies. Phosphorous is especially important in the process of photosynthesis, a cannabis plant’s metabolism, and the ability for the plant to absorb nutrients.  A phosphorous deficiency makes plants more vulnerable to pathogens and is identified by leaf discoloration from green to a purple-reddish hue. Potassium helps plants grow earlier, fight disease better, and use water more efficiently.  Plants malnourished in potassium will show this deficiency with yellowing leaves.  However, a potassium deficiency distinguishes itself through the location of the yellowing; yellowing begins at the leaf’s edges. Fertilizer for growing plants Most fertilizer bottles will show a numbered N-P-K value to indicate the quantity of each of those nutrients in that order.  For example, a fertilizer that says 2-1-6 contains 2% nitrogen, 1% phosphorous, and 6% potassium. During a cannabis plant’s vegetative stage, it needs a high quantity of nitrogen, a medium quantity of phosphorous, and a high quantity of potassium.  Once your plant begins to flower, it needs much less nitrogen, but the values remain the same for the other two nutrients.  This is why buying a slow-release, general purpose nutrient formula throughout the duration of your growing season is a bad idea; too much nitrogen during the flowering stage will inhibit bud growth.

Guidelines for your N-P-K ratios based on each stage of cannabis’ growth cycle:

Seedling: 1-2-2 Vegetative: 3-1-2 Flowering: 1-4-5 Ripening: 0-2-0

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Secondary Nutrients

People are pretty familiar with the importance of nitrogen, phosphorous, and potassium, but other macronutrients including calcium, magnesium, and sulfur are important too.  These nutrients are so important that they are often referred to as secondary nutrients rather than micronutrients. Calcium better enables plants to absorb other nutrients, maintain proper cell structure, and facilitate photosynthesis. Magnesium plays a vital role in the creation of chlorophyll, making it essential in a plant’s ability to photosynthesize. Sulfur aids in the development of strong roots, chlorophyll, and plant proteins during the cannabis plant’s vegetative stage.


Your cannabis will also benefit from very small quantities of micronutrients including zinc, iron, manganese, molybdenum, chlorine, cobalt, silicon, boron, and copper. Zinc helps to strengthen your plants’ leaves, stalks, and branches.  It is also responsible for the creation of enzymes and the growth hormone, auxin. Iron is particularly beneficial for young plants as chlorophyll synthesis and enzymes responsible for growth need iron. Manganese enables plants to use nitrates in protein creation, to disintegrate enzymes, and to create chlorophyll. Molybdenum, like manganese, gives plants the ability to use nitrates in protein production. Although toxic in high concentrations, very low amounts of chlorine play an essential role in plant osmosis, photosynthesis, and immunity. Cobalt is necessary for overall plant growth, CO2 absorption, and leaf disk expansion. Silicon stimulates plant growth and can result in higher yields. Boron plays an essential role in multiple aspects of plant growth including calcium absorption, pollen germination, maturation, seed production, protein production, and plant structure formation. Copper is necessary for bud formation. Although each of these micronutrients are considered essential for healthy plant growth, it likely isn’t necessary for you to supplement them unless you have a clear deficiency.  They are already present in most soils and are truly beneficial in very small amounts.

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How Cannabis Absorbs and Transports Nutrients

How plants absorb Phosphorous, Potassium and NitrogenNutrients are absorbed in the roots through osmosis.  In plants, osmosis refers to the transfer of ions from water through the plant’s cell wall and into the cell.  This osmotic pressure—the movement of nutrient ions during osmosis—is a smart process.  Osmotic pressure moves according to the concentration of nutrients on each side, from the side with the highest concentration of ions to the one with the lowest. For example, when the cannabis plant uses phosphorous, the concentration of that ion is lower on the plant cell side than it is on the water side.  Osmotic pressure then enables the plant to absorb phosphorous from the water.  If the concentration of phosphorous is the same inside of the plant cell as it is in the water, nothing happens.  There is no osmotic pressure. However, if there are more ions in the plant cell than there are in the water, the phosphorous will transfer to the water to create balance, causing a phosphorous deficiency. Once the nutrients are absorbed by the roots into the plant cells, they must move upward through the plant to get their work done.  The pressure created by salts and oxygen present in the water as well as the leaves’ pores enable the nutrients to move through the cannabis plant. There are factors that can slow or stop the absorption and movement of nutrients.  If the humidity is too high, the leaves will struggle to create the right amount of pressure through evaporation, and the plant will absorb fewer nutrients.  If it is too hot, too much water may evaporate, and the plant will lose nutrients as a result of this excess evaporation.  This is why keeping cannabis at the right temperature is so important.  Reducing the plant’s sweating allows it to use the nutrients you’ve worked so hard to provide it. The materials you feed your plants with are converted into energy and the nutrients needed to create new plant cells and maintain existing ones.  The type of plant cells created depends on the stage of growth the plant is in; hence the different N-P-K ratios for each phase of cannabis growth. Nutrients play a vital role in the overall health of your cannabis plant.  Equipping yourself with knowledge about these essential elements of cannabis growth will bring you that much closer to an abundant, healthy harvest.