Cannabis nutrients NPK are essential for healthy growth

Growing cannabis can seem like a daunting task at the first glance. Everyone talks about light cycles and nutrients, making it look like a nightmare for a newbie grower. However, growing cannabis is very similar to any other household plant. It has its differences which is what defines cannabis. In this feature we will tackle a segment that many beginner growers find hard to grasp when growing marijuana for the first time. What are the best cannabis nutrients to ensure that you get those big buds and big yields? Everything will be answered here.

Organic or inorganic cannabis growing?

This is the biggest question you need to ask yourself when you are starting your own cannabis nursery. Are you going to be an organic grower or will you be using synthetic fertilizer to boost your plants? The answer to this does not change a whole lot as it still falls within context. But what changes are the methods of administration. Because, at the end of the day, organic or inorganic still break down to the same base nutrients that we will be speaking of.

Factors to consider when it comes to nutrients

Adding nutrients is not rocket science but at the same time it is also not a game of guessing. Adding random amounts is the main cause of plant burns. In this section we’ll take into consideration the most decisive factors when it comes to nutrients and supplements.

The ratio

Different types of fertilizers have different types of chemical ratios. Before buying a particular product from your local store or online, check whether the ratios are appropriate. There are different chemical ratios for different types of fertilisers. Flowering brands have entirely different compositions from growth fertilisers. Ratios play a big role in NPK fertilizers ( X:X:X).


This is what makes up your fertiliser. The nutrients that are in soil will get absorbed by your cannabis plant. When growing marijuana it is important you periodically replenish these lost nutrients so that your plant does not starve to death. The composition of your plant add-on dictates which nutrients you will use. It is important to add in nutrients but it is equally important not to saturate the soil by doing so. Make sure your fertilizer has the nutrients that you need to add in. The most common type of composition when growing cannabis for big yields is the NPK composition.


Pick a brand that you deem is good and stick to it. Mixing up nutrients from different companies can have adverse effects on your plants. Therefore stick to something you like and are comfortable with.

Growing medium

Most of you are growing cannabis on soil. But this is not the only medium for growing. Hydroponics are a popular way to grow cannabis as well. There are different nutrients for both these mediums. Make sure you do not mix these up. Hydroponics are much stronger than soil based fertilisers because of the lack of a grounding substance.

What are the most important nutrients for growth?

All plants have three major nutrients that they require for growth. A deficiency in them could result in stunted growth and a whole lot more problems as time progresses. NPK or Nitrogen, Phosphorus and Potassium are the three main nutrients you need to look out for so we will discuss these first.

Major nutrients for plant growth


The single most important nutrient when growing marijuana. Cannabis plants love nitrogen and they absorb nitrates from the soil insanely fast. If you are growing organically a good way to get nitrogen into the soil is by planting companion plants alongside your cannabis. Legume plants (beans & peas) naturally deposit nitrates into the soil by absorbing nitrogen from air. Nitrogen aids the creation of proteins and that helps the plant to grow. If you want big buds and high yields, having stable amounts of nitrates are important.


Phosphorus is what enables the plants to create energy for themselves. It plays a major factor in photosynthesis. It is also needed for growth and other metabolic purposes. Without phosphorus you are essentially starving your plant.


Potassium hardens the plant and gives it resistance by strengthening the roots of the plant. This makes it able to survive those rough cold and dry seasons. Lack of potassium can cause your plant to wilt and collapse. Other than its role in increasing a plant’s resistance to disease, it is also known to improve the quality of the buds.

Secondary and micronutrients

NPK are the big three when it comes to nutrients. However that does not mean that plants will be happy with just these. Micronutrients are also needed but in smaller quantities than NPK, but nevertheless they are important in the growing and survival of a plant. When growing cannabis it is important that you balance out all these substances.


Promotes the stabilisation of plant cells while aiding photosynthesis and metabolism of carbohydrates.


Important for the production of chlorophyll and the creation of amino acids/proteins. Also boosts plants resistance to disease.


Calcium plays a major role in cell wall development. The substance can also reduce soil salinity and helps to boost water penetration.

Other than these three major secondary nutrients there are a few more that increase a plant’s quality; Zinc, Iron, Copper chlorine, Boron and Manganese are some of it.

Adding in cannabis nutrients

There are 3 major stages in a plant life cycle. These are the seedling phase, the vegetative period and the flowering stage. Different parts of the life cycle require different kinds of fertiliser to aid its growth. All stages of growth and harvest need to be properly maintained to increase yields.


The most vulnerable stage of a plant when growing cannabis. You won’t be able to achieve those big yields and big buds if your plant dies here. Therefore it is important to take special care during cannabis seedling stage. Do not add anything to the plant during its seedling stage. Letting it survive off what’s present in the ground is the best thing to do.


Once your seedling grows 4 true leaves it has reached the vegetative phase. Now the plant is capable of adapting to changes and absorbing some of those nutrients you add. To start with add in some NPK fertiliser on a 2:1:2 ratio (you can buy fertilizers with this ratio online or from your local gardening store).

6 weeks into the vegetative growth phase you can start adding in more nitrates to boost its growth. During this period the cannabis plant will see its biggest growth spurt. Therefore it is important to make haste while the sun shines. We recommend a fertilizer with the ratio 10:5:7. The increased nitrates will make your plants grow luscious leaves and thick foliage, preparing for an impressive flowering stage.

When nearing the end of a plant’s vegetative growth cycle it is important to lower the amount of nitrates and promote flowering. For this we recommend the fertilizer with the ratio 7:7:7.


The most exciting stage when it comes to growing marijuana. The big buds you dreamed of will start appearing during this stage. During the flowering stage, cannabis plants require copious amounts of potassium. At the start of the flowering period start off with a fertiliser that has a 5:7:10 ratio. This is great for the first few weeks, but when reaching midway of the flowering stage, it is important to increase ratios. During this period it is most growers opt to go with a 6:10:15 ratio fertilizer.

As you reach the end of the flowering stage, it is important that you crank it up to help your plants bloom to their limits. The recommended fertilizer ratio for this period is 4:7:10.

How to prepare your cannabis fertilizer

Preparing your fertiliser for growing cannabis is an easy task. Just follow the steps below in the order given.

  1. Get clean water that is unchlorinated (Leave the water out for a day should do the trick). Heat the water up to 22 degrees. This is the best temperature for plant feeding and will help the roots to absorb everything at a much quicker pace.
  2. Add the fertiliser into the water following the manufacturer’s instructions. I would recommend purchasing a PPM & a pH meter so that you can get accurate readings on the level of concentration in the mix. 
  3. If the pH is too high then you can tone it down by adding in a little bit of Nitric/phosphoric acid. Once again signifying the importance of a pH meter.
  4. Add in the nutrients into the soil

Understanding deficiencies

Deficiencies of nutrients create visible stress on the plant. This usually means a micro/secondary nutrient is lacking in the plant’s soil system. Luckily this is easy to treat if you manage to pick it up quickly, stopping any long term damage to your cannabis plant.


Plants like nutrients but overfeeding is never the way to go. It will just kill your valuable plants. Always stick with the recommended dosage at all times. The signs of overfeeding include nutrient burn on leaves, tips that are bent upwards and discolouration. In the event of an overfeed, always flush the roots and stabilise the soil pH.

Nutrient deficiency

Different nutrients when lacking give out different symptoms. However, if you notice any visible changes when growing cannabis, always carry out a flush. This is because it could be a nutrient lockout, where nutrients have got concentrated around the roots. After a flush restore the plants soil by adding in nutrients following the recommended dosage.

Nutrient burns

Burns are a sign that overfeeding has gone out of control. The symptoms for this vary depending on the severity. Clear signs of nutrient burns are dark leaves with bright tips that curve upwards at an angle close to 90 degrees. There might be discolouration of the branches where they reach a deep red or a shade of magenta. Upon seeing burn symptoms, immediately flush. Keep the plant stable for a minimum of 7 days before you readminister any nutrients.

What if you are an organic grower?

Organic fertiliser is much safer when compared to synthetic nutrients. These organic compositions decay and release their nutrients into the soil over time. This removes any possibility of burns or overfeed. However, plants on organic fertiliser tend to lack the boost that synthetic nutrients provide. Synthetic fertilisers increase yields rapidly, and get absorbed by plants much quicker. If you are an organic grower pay close attention to the state of the plants. If they show any symptoms of nutrient deficiency, add in the relevant nutrient to resolve it.

This wraps it up

Growing marijuana is not hard. Cannabis plants are some of the fastest growing and most responsive plants in the world of flora. By sticking to the relevant instructions and giving your plants plenty of light and ample water, you can too achieve those big yields and big buds that you dream of. The most important tip to increase yields is to remain dedicated to your nursery!

Ready made grow kits

To make prep work less daunting, you can also purchase ready made grow kits from online seedbanks. There are different kits available, depending on whether you are looking for a beginner grow kit, high yield grow kit, or other types of grow kits.

Joe Musgrave

An avid 420 enthusiast, grower, smoker and writer. Joe writes non stop, sharing his extensive knowledge in the field of cannabis with the wider online 420 community through blogs like ours at High Yield Strains.

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