Cannabis Nutrients & Fertilizer for Growing

Water dripping from a cannabis plant leaf

Cannabis plants need lots of nutrients to grow properly. While they will still grow as long as they have plenty of light and water, good soil, and a temperate environment, adding nutrients will help your plants thrive so they can grow healthy and strong.

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The Importance of Cannabis Nutrients

If you want high-quality buds, growing cannabis requires more fertilizer or nutrients than most regular crops.

When growing outdoors, you typically add powdered nutrients into the soil when you transplant the cannabis plant. These nutrients give the plant everything it needs over its life cycle. And if it later requires more nutrients, we add additional fertilizer to the top of the soil or mixed in the irrigation water.

When growing indoors, we typically use liquid nutrients and add them to the water we use to hydrate our plants. This method is more time-consuming, you’ll have to measure, mix, adjust pH, and water your plants multiple times per week.

You don’t want to use nutrients designed for outdoor growing for inside plants, though, as the synthetic mineral salts can cause damage to the beneficial soil bacteria.


Key Cannabis Nutrients

The three primary nutrients your cannabis plant will need are:

  • Nitrogen
  • Phosphorus
  • Potassium

In addition, your cannabis plants need smaller amounts of these micronutrients:

  • Calcium
  • Magnesium 

Cannabis plants need varying amounts of all of these nutrients through their growth stages. For example, during the vegetative stage, your plants will need extra phosphorus and potassium to produce bigger buds.


This nutrient is primarily responsible for your cannabis plant’s development through the vegetative stage. It’s an essential part of chlorophyll—without it, your plant can’t turn sunlight into energy, meaning it will stop growing.

Nitrogen also affects the plant’s amino acids that help the plant produce proteins. Without them, your cannabis plant will grow weak and fail. In addition, nitrogen is part of ATP, allowing plant cells to control how they use energy.

Finally, nitrogen is a crucial component of nucleic acid creation, an essential DNA ingredient that allows the plant’s cells to grow and multiply.


This nutrient is vital for helping your cannabis plant produce large and healthy buds. Phosphorus’s key role is to make the necessary nutrients available for your plant to take in and build its structure from the roots to the flowers.

Without enough of this nutrient, your cannabis plants will have underdeveloped roots, and might not flower at all. Early signs of deficiency show up as purple hues in the leaf's veins.


Potassium plays a large role in various parts of your cannabis plant’s system. It’s essential for a healthy, growing plant. This nutrient helps osmoregulation, which regulates the water and salt concentration in your cannabis plant.

It accomplishes osmoregulation by controlling when the plant’s stomata open and closes, allowing it to exchange oxygen, water, and C02.

Potassium also triggers the plant to produce ATP, which stores energy in the form of glucose. Your plant will use that glucose for energy as it grows.

Without sufficient potassium levels, your plant will appear burnt, and it will be too weak to grow—this happens when it can’t regulate the exchanges we mentioned above.

Related: Remove Pests & Bugs in Your Grow Tent


This nutrient is responsible for keeping your cannabis plant’s cell walls together. Without it, your plant won’t function correctly, and its new growth won’t develop properly.

If your plant doesn’t have enough calcium, you’ll notice curled leaves, rusty spots, and the stunted growth of new leaves.


Magnesium—which acts as the central molecule for chlorophyll—helps your plant turn sunlight into energy. A magnesium deficiency means a plant that lacks glucose and energy.

Once this nutrient creates glucose, it also helps metabolize it so that plants can use it. Without enough magnesium, you’ll notice discolored veins and yellowing leaves.


How to Use Cannabis Nutrients & Fertilizers

You’ll notice that nutrient packages and fertilizer bags will have three numbers at the top of the packaging. In order, these numbers stand for nitrogen (N), phosphorus (P), and potassium (K). For example, if it says “10-8-5” it will contain 10% nitrogen, 8% phosphorus, and 5% potassium by weight.

In the vegetative stage, you want to look for 9-4-5 fertilizers. Or you can look for “grow” solutions.

In the flowering stage, you’ll want to reduce the nitrogen and increase the phosphorus and potassium—look for 3-8-7 fertilizers. Or you can look for “bloom” solutions.

Liquid Cannabis Nutrients

Liquid nutrients are more common for growing indoors, but you can use them outside, too. They are fast-acting—if you overdo it with liquid nutrients, you can damage your plant.

To use them, you’ll need to mix the nutrient solution with water (ensure you use the correct ratios stated on your fertilizer’s label!), and water your plants with the mixture.

You should track these three things:

  1. How much water do you use for all of your plants
  2. Which nutrients and how many of each do you use
  3. How often do you water your cannabis plants

You don’t want to use the nutrients every time you water—more like every other watering (or even less, in some cases). It all depends on your soil’s complexity and your plants’ health.

Organic Cannabis Fertilizers

These nutrients come from organic sources like vegetable and animal waste. They also often include sediments like gypsum that are beneficial for your cannabis plant and its soil. Most often, you’ll use organic fertilizers for growing outdoors, and they typically come in a powder form.

Organic fertilizers are also more forgiving than liquid nutrients—they contain less soluble nutrients and more parts that are beneficial to the soil’s organisms.

You can find these at any nursery and simply mix them into the soil before you plant your cannabis plants. When done correctly, all you’ll have to do is ensure you water them throughout the growing process—all of the nutrients are now in the soil already.

The best organic fertilizers to look for when growing cannabis plants are:

  • Blood meal and fish meal for nitrogen
  • Bat guano and bone meal for phosphorus
  • Kelp meal and wood ash for potassium
  • Dolomite lime for magnesium and calcium
  • Epsom salts for magnesium

You can also find commercial soil blends that already contain the right mixture of these nutrients.

Now you’re ready to start growing healthy cannabis plants that are sure to produce massive buds—Don’t forget the rest of your grow gear!

Related: Cannabis Grow Tents: Buyer’s Guide


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