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Nitrogen and Cannabis Plants: The Ultimate Guide

by | Jul 25, 2022 | Cannabis, Getting Started, Nutrients, Troubleshooting

Nitrogen is one of the most essential nutrients for cannabis plants. Nitrogen deficiencies are common, nitrogen excesses are rare, and nitrogen can have a direct impact on your crop yield. This article will teach you everything you need to know about nitrogen in cannabis grow including how it affects plant health, signs of nitrogen deficiency or excess, prevention methods, and how to fix nitrogen problems if they occur.

What is nitrogen?

Nitrogen is an element that is the most naturally occurring in our atmosphere. Nitrogen is the nutrient responsible for nitrogen fixation, which converts nitrogen gas in our atmosphere into nitrogenous compounds that can be used by living organisms. Plants need nitrogen to grow and produce healthy flowers and buds.

Why do cannabis plants need nitrogen?

Cannabis needs nitrogen to produce amino acids, chlorophyll, and sugars which means it plays an essential role in photosynthesis. Amino acids are the building blocks of proteins that form enzymes and transport nutrients around the plant. Chlorophyll is the green pigment in leaves responsible for photosynthesis and it’s what makes plants appear green from a distance. Sugars produced by nitrogen play an important role in the formation of buds and flowers. When the plant receives nitrogen as nitrates, it will turn it into sugars which are used as building blocks for terpenes, cannabinoids, nitrogenous compounds, and other molecules. Cannabis plants will typically only use the nitrogen they need, so nitrogen deficiencies are more common than nitrogen excesses.

What are mobile nutrients and immobile nutrients?

Mobile nutrient sources can move through a plant’s vascular system, while immobile nutrients are fixed to one part of the plant and must be replaced by fertilization or uptake from other plants. Marijuana plants that need nitrogen that is mobile in the growing medium or they will show nitrogen deficiencies in lower leaves when nitrogen levels are too low.

Is nitrogen a mobile or immobile nutrient?

Nitrogen is a mobile nutrient because it can move from older leaves to younger ones through cannabis photosynthesis, although nitrogen will mostly be used by the newest growth. Nitrogen deficiencies are most common in young plants because nitrogen is used up faster than it becomes available. This is why nitrogen is most important during the vegetative phase.

What are macronutrients and micronutrients?

Macronutrients, which are nitrogen, phosphorus, and potassium, are required by the plant in larger quantities compared to micronutrients, such as calcium, magnesium, and iron, among others. Macronutrients can be either mobile or immobile. The reason they are called macronutrients is that nitrogen, phosphorus, and potassium are needed in much larger quantities by your cannabis plants than micronutrients.

Is nitrogen a macronutrient or micronutrient?

As noted above, nitrogen is a macronutrient because it’s required in larger quantities by plants compared to micronutrients that are needed in smaller amounts.

What does this mean for cannabis plants?

Nitrogen is required for plant growth, but nitrogen deficiency results in stunted plants because nitrogen stimulates them to grow faster than cannabis plants can use them up. If you’re growing indoors with supplemental lighting then there’s usually too much light energy available during the veg and early flowering stages. This excess light energy will speed up nitrogen fixation, resulting in nitrogen deficiencies even if you’re giving your plants nitrogen-rich nutrients.

What are the signs of a nitrogen excess in cannabis plants?

Nitrogen excesses are rare and nitrogen toxicity is unlikely if you’re using cannabis-friendly nutrients. You’ll notice the symptoms of nitrogen toxicity as nitrogen toxicity progresses. Symptoms of nitrogen toxicity include:

  • dark green leaves that will start at the bottom of the plant and work their way up as the toxicity progresses
  • weak stems
  • shiny leaves
  • leaves “claw”, meaning the leaf tips curl down, and eventually the whole leaf
  • leaves will rarely “cup” as well, meaning they turn up instead of down

After some time of not treating the issue, the leaves will eventually yellow and die

How do I fix a nitrogen excess in my cannabis grow?

If you are experiencing excess levels of nutrients such as nitrogen, you should flush your system with clean, pH’d water. If you don’t know your pH then flush with a plain water flush for one week, then check to see if your nitrogen level is where it should be. Overfeeding can cause a salt buildup which will lead to nutrient lockout and flushing is your best solution for your plants.

What are the signs of nitrogen deficiency in cannabis plants?

The most common sign of nitrogen deficiencies is yellowing lower leaves, which will start at the bottom of the plant and work their way up. Nitrogen deficiencies are most common during the vegetative phase when nitrogen is used up faster than it becomes available because plants use nitrogen to grow stems and leaves. Nitrogen deficiencies can also occur when nitrogen is limited in the growing medium or due to a pH lockout, which prevents plants from absorbing nitrogen and other nutrients.

The most common signs of nitrogen deficiency are:

  • yellowing lower leaves that work their way up the plant, eventually they turn soft and distort or “fold” themselves
  • leaf color on non-yellowing leaves appearing lime green
  • fewer bud sites resulting in a lower yield
  • stunted growth with smaller leaves
  • premature flowering which also causes a lower yield.

if untreated, leaves will eventually, turn brown, die, and fall off the plant. It is important to note that although the leaves will turn brown and die, they will not have brown spots. If your plants have brown spots, they are probably suffering from another nutrient deficiency.

How do I fix nitrogen deficiency in my cannabis grow?

Nitrogen deficiencies can be corrected with nitrogen-rich supplements like guano, blood meal, or fish emulsion. Growers can also use nitrogen-rich additives to the water supply to also supplement their plant’s nutrients until they reach the optimal level. Should your plant not show any progress after a couple of weeks of having nitrogen added as a supplement, then there could be another problem such as nutrient lockout. If nitrogen deficiencies are due to a pH lockout, then adjusting the pH will allow nitrogen into the plant.

How do I prevent problems with nitrogen during my cannabis grow?

Prevent problems with nitrogen in your cannabis grow by giving nitrogen to the plant during vegetative growth. Vegetative plants need nitrogen for healthy stem and leaf development, so nitrogen deficiencies are most common during vegetative growth.
Give nitrogen to plants that are in the flowering stage, but nitrogen deficiencies can still occur even if nitrogen is abundant in the growing medium. Nitrogen deficiencies during flowering are most common when nitrogen-rich amendments have been used up and nitrogen is not supplemented to the plant.

Nitrogen deficiencies during flowering can be prevented by giving nitrogen supplements such as guano, blood meal, or fish emulsion during both the vegetative and flowering phase of a plant’s life.

Nitrogen excesses are rare and unlikely when using professionally manufactured hydroponic cannabis nutrients or dry amendments but they still do happen. However, should you run into a problem with nitrogen toxicity, you can always flush your plant with PH’d water. Nitrogen can also accumulate in the plant’s system if nitrogen is not flushed regularly during a grow, especially during the flowering phase. Growers should always check nitrogen levels in their plant’s system before they flush nitrogen out of a growing medium so that there won’t be nitrogen deficiencies due to the nitrogen being flushed. Nitrogen excesses will show signs of nitrogen toxicity, which is usually a dosage issue.


Nitrogen is the most abundant element in our atmosphere and is needed by cannabis plants because it is a mobile macronutrient. It is especially needed during the vegetative stage of growth, although a lower amount of the nutrient is still needed during flowering too.

Cannabis plants can have too much nitrogen though and they will show it in the form of nitrogen toxicity. If your plants have an excess of nitrogen, the leaves will usually claw and be an unnatural dark green. To fix this, all you need to do is flush your plant with PH’d water.

If your plants are suffering from a nitrogen nutrient deficiency, the leaves at the bottom will turn yellow and work their way up the plant while the non-yellowing leaves may turn bright lime green. The way you can fix a nitrogen deficiency is by adding guana, blood meal, or fish emulsion to your medium or adding more nitrogen-rich nutrients to your water for nutrient solutions.

To prevent problems with nitrogen during your grow, make sure your plant has enough nitrogen, especially during the vegetative growth phase. Also, remember to always PH your water to ensure it is taking in all the nutrients it needs to grow. Thank you for reading our article, should you have any further questions please refer to our articles about overwatering, nutrient lockout, how to PH your water, and other cannabis nutrient deficiencies.

To learn more about growing cannabis at home consider checking out our guides on: Getting Started, Troubleshooting, and Optimizing your Grow or search our Knowledge Base.

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