The best cannabis growers love their plants. They regularly check on them, attend to their needs, and make sure that the plants have access to everything they need to grow up to be strong and healthy. They don’t really need those things but, you do need specific nutrients for growing cannabis.

There are a lot of things a grower needs to have full control over. Light, water, and oxygen are the absolute basics. But what you need to remember is that to grow plants that produce a significant yield, you need to make sure they have more than just the basics. They need to have the right kind of nutrients available to them at the right time.

The three most essential cannabis growing nutrients, sometimes called the big three, are Nitrogen, Phosphorus, and Potassium. On top of that, it is recommended your plants have access to Calcium, Magnesium and, and Sulfur. 

Does it feel like you’re back in the chemistry class? Don’t worry. It’s simpler than you might think. Let us break it down for you.

Why Does a Cannabis Plant Need Nutrients?

Cannabis, just like any other plant, needs nutrients to survive. If you want your plants to thrive, not just survive, you have to feed them the right amount of nutrients. 

Feeding nutrients to your cannabis plants can be tricky, as it’s easy to both over and underfeed them. While cannabis will usually give out signs of malnutrition through its appearance, it is often challenging to pinpoint which ingredients are being administered wrongly. 

Many first-time growers think that when cannabis plants die, it is mostly due to environmental factors of cannabis cultivation. That is not the case. The most common cause of cannabis plants’ death is a grower error, often related to the improper management of the nutrients.

So, keeping this in mind, let’s start by learning more about the nutrients your cannabis plants want and need!

The Big Three: Nitrogen, Phosphorus, and Potassium.

These three cannabis growing nutrients are the most important ones to know about. When not administered in the correct amounts, they can cause significant damage to your growth. They are often referred to as N-P-K, with N standing for Nitrogen, P for Phosphorus, and K for Potassium. 

What makes cannabis cultivation a bit tricky is that your plants will need different levels of various cannabis growing nutrients depending on the grow phase they are in. 

Let’s take a look at each one of these three nutrients. 

Nitrogen

Your plants will need access to Nitrogen throughout their entire life. While cannabis needs way more Nitrogen during the vegetative state than during the flowering stage, it will die if it lacks it entirely, no matter which growing phase your plants are in. 

Nitrogen is essential for photosynthesis. It makes it possible for your plants to grow strong stems, branches, and leaves. It also increases their ability to resist pests and other diseases, and even some challenging weather conditions (for example, frost).  

How to Spot Nitrogen Deficiency:

• Mature leaves become light and then often turn yellow
• The discoloration then moves to younger leaves (usually starting near the base of the leaf)
• Leaves can curl and wilt
• Unusually small buds 
• Small yield

Phosphorus

Phosphorus is a part of the big three because it impacts every aspect of cannabis growth and development.

It facilitates early-stage root development, flower formation, yield and is necessary for the plant to perform photosynthesis. 

Phosphorus deficiency can make it more challenging (if not impossible) for your plants to absorb other nutrients, even if they are easily available. It can result in stunted growth and has a direct, negative impact on the size and quality of your yield. 

Your plants will require medium levels of phosphorus in the vegetative stage and medium-to-high levels during the flowering stage.

How to Spot Phosphorus Deficiency:

• Mature stems become purple, and leaves turn dark 
• Stunted growth, leaves might curl and droop
• Occasionally, leaves might turn purple as well

Potassium

The last one of our three most essential cannabis growing nutrients is responsible for supporting your cannabis plants’ early growth, helping fight diseases, and using water efficiently.

High levels of potassium encourage the production of healthy cell walls, making your plants more resilient to various pathogens, including mildew. 

Like with any other nutrient, the amounts have to be just right. If you exceed the amounts of potassium needed in your plants, Calcium and Magnesium will get locked-up. If you do not deliver enough potassium, your plants will weaken or die in the worst-case scenario.

The potassium levels will need to be high throughout both the vegetative and flowering stages.

How to Spot Potassium Deficiency:

• Leaves look dull, with brown leaf tips and brown spots, especially noticeable on more mature leaves
• Younger leaves might curl due to dehydration caused by potassium deficiency
• Reduced flowering and a higher chance of being infected by pests or diseases 

Secondary Nutrients: Calcium, Magnesium, and Sulfur

If you are growing cannabis indoors or on a big scale, the chances are that your plants will need you to supplement their secondary nutrients.

Calcium, Magnesium, and Sulfur are consumed in high quantities, but their natural supply is limited, so it is your responsibility to feed your cannabis plants with these three nutrients. 

Magnesium (Mg)

Magnesium deficiency is a widespread problem among growers. That is because cannabis has a huge appetite for Magnesium! 

Magnesium is an essential nutrient because it supports your plants in absorbing light energy and utilizing all of the nutrients your plants need. It is also crucial for setting off the flowering stage. 

How to Spot Magnesium Deficiency:

• Symptoms are very slow to show (weeks might pass before you start noticing any)
• Leaves turn yellow with brown/dark red spots
• The plant looks sad and sick, with drooping branches
• Yield smaller than expected

Calcium (Ca)

Calcium, a nutrient crucial for facilitating Nitrogen and the proper flow of sugars within cannabis plants, helps build strong roots and cell walls.

It is one of the few nutrients which can not be distributed evenly between different parts of the cannabis plant. In other words, if you provide your plants with a lot of Calcium and then suddenly stop, the newly grown parts of your plants will not have access to the stored Calcium. 

Your roots will need to access new amounts of Calcium to feed the newly grown parts of the plants. That’s why it’s so important to supply the appropriate amounts of Calcium throughout the whole growing process.            

How to Spot Calcium Deficiency:

• More likely to occur in wet climates or in hydroponic grows
• Leaves (mostly lower ones) curl and have dark yellow spots
• Brown borders on the leaves
• Root tips start dying.

Sulfur (S)

While sulfur is an essential nutrient, you will hardly ever be required to supplement your plant with it. Most fertilizers already contain sulfur, and even single nutrients you purchase (for example, Magnesium) have sulfate added to it. As a result, a sulfur deficiency is very rare. 

Sulfur is vital for a few reasons. It plays a role in managing the water pH, supports root growth, and helps your plant access and absorb other nutrients and vitamins, crucial for its healthy development.

How to Spot Sulfur Deficiency:

• Leaves (especially the young ones) will first turn lime green and then yellow. 
• Leaves will start drying out
• The flowering phase slowed down, and the potency reduced

Conclusion

Just like any other plant, cannabis requires nutrients to both survive and thrive.

The three most important cannabis growing nutrients, also referred to as macronutrients or N-K-P, are Nitrogen, Phosphorus, and Potassium. A deficiency of any of these nutrients will significantly impact your grow and can go as far as to kill your plants. 

There are plenty of other ingredients your plants need to guarantee strong growth: Calcium, Magnesium, and Sulfur being the most important ones. While a deficiency in one of the three is unlikely to kill your plants, it will have a big impact on the size of your buds and the size of your yield, as well as the potency of the final product.

The good news is that cannabis plants have a good way of letting you know when something is missing in their diet. In most cases, you will be able to tell if something is wrong with your cannabis plants just by looking at them and analyzing the leaves.

If you see any abnormalities on your leaves or stems, make sure to revert to this article and look for specific symptoms mentioned above. The sooner you supplement you grow with the correct missing nutrients, the bigger your chances are of saving your grow in time to still get an excellent yield.

Check out our post on growing cannabis outside next.