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Nitrogen Deficiency In Cannabis Plants

We explore what a nitrogen deficiency looks like in your weed plants. Read on to learn how to solve this issue and prevent the occurrence from happening altogether.

HOW TO IDENTIFY?

Growing cannabis is a therapeutic act that takes quite a lot of attention to detail. One of the requirements to successfully grow a large cannabis crop of good quality is applying the right concentration of nutrients. If your plant begins to lack the required amount of nutrients during any point of the grow cycle, it may begin to exhibit symptoms of deficiency. If left untreated, these deficiencies may cause harm to the plant’s health and reduce yields.

THE IMPORTANCE OF NITROGEN

One of the most important nutrients that your cannabis plants need is nitrogen. Nitrogen is vital for plant health because it is a major component of the green pigment found within plant leaves known as chlorophyll. Chlorophyll plays a crucial role in photosynthesis, the process by which plants convert sunlight into energy in order to survive. Nitrogen also serves as a major component of amino acids within plants, which are the building blocks of proteins. Nitrogen is also an important component of nucleic acids like DNA, which plants need in order to grow and reproduce.

NITROGEN DEFICIENCY SYMPTOMS AND SOLUTIONS

It is quite clear to see how important nitrogen is to your cannabis plants and why a deficiency could be so damaging. Luckily, nitrogen deficiency is quite easy to detect if you know what to look for.

One of the key signs of nitrogen deficiency within your weed plants is yellowing leaves. The older and lower leaves on your plants will start to become yellow, wilt, and drop off. This is because the younger leaves higher up the plant will start to steal the nitrogen from these older leaves. The plant prioritises higher leaves as they receive the most light, contributing greatly toward photosynthesis.

This may not always be a concern. It is normal for these lower and older leaves to start becoming yellow and dropping off towards the end of the grow cycle as nitrogen is diverted toward the buds. It is time to worry when your plant’s leaves start to yellow and drop off rapidly during the vegetative phase. If this yellowing starts to move up the plant in a climbing manner, then a problem is most likely present.

A solution to this problem is to provide your plants with a balanced nutrient product. There are many formulas available that provide an array of key nutrients to your plants, making sure that nitrogen levels are kept at a healthy level all the way through the vital vegetative phase.

NITROGEN TOXICITY

Some novice growers may be shaken at the sight of nitrogen deficiency symptoms, causing them to go overboard when adding nitrogen to their soil. However, be forewarned: the pendulum can swing the other way when it comes to nitrogen, with too much also causing a problem in plants.

When a grower accidentally puts far too much of the nutrient into their soil, it can cause the phenomena of nitrogen toxicity. During the vegetative phase of the grow cycle, it is rare that plants will develop nitrogen toxicity unless a huge amount is given to them. Nitrogen toxicity is more common during the flowering phase, as plants require lower levels of nitrogen at this point. Symptoms of toxicity can manifest in shiny leaves, much darker green leaves, weak stems on plants, much slower overall growth and clawing of leaves. Clawing is a typical occurrence that involves the tip of leaves losing vigour and folding downwards, resulting in a claw-like appearance.

Nitrogen is a key nutrient within cannabis plants and is required for many processes. Here is how to detect a deficiency, with some helpful solutions.

Nitrogen Deficiency

Problem: A cannabis nitrogen deficiency will cause the older, lower leaves on your plant to turn yellow, wilt away and eventually die. The plant typically appears pale or lime-colored.

The yellow leaves of a nitrogen deficiency may show signs of brown, and they will usually become soft and sort of “fold” in, before possibly turning crispy but ultimately falling off on their own.

Example of cannabis Nitrogen deficiency – yellow bottom leaves. Almost all plant nutrients contain Nitrogen

Nitrogen-deficient plants often appear pale or lime-colored. The leaves on this marijuana plant don’t have obvious leaf symptoms like spots or markings, but they are pale all over the whole plant. Almost lime green. The light-colored leaves are a sign the plant needs more Nitrogen (and nutrients in general). On the flip side, plants that are receiving too much Nitrogen turn dark.

If the yellowing leaves are at the top of your plant or the yellow leaves are mostly new growth, then you probably don’t have a nitrogen deficiency. Nitrogen deficiencies usually affect the oldest, lowest leaves first, or the entire plant becomes light colored.

Nitrogen is a mobile nutrient, which means it can move throughout the plant as needed. Cannabis needs nitrogen to keep leaves green and make energy from light. All new leaves get plenty of nitrogen to make them green and help with photosynthesis. The leaves that get the most light are the newest, youngest leaves, so the plant “wants” to give those leaves priority for getting light.

If new leaves aren’t getting enough nitrogen, the plant will start to “steal” nitrogen from the older, lower leaves, so that it can give it to newer leaves. This is what causes the yellowing and wilting of a nitrogen deficiency.

It’s relatively normal for your cannabis plant’s leaves to start turning yellow towards the end of your flowering cycle as the plant becomes nitrogen deficient while creating buds.

However, if your cannabis plant is losing lower leaves fast due to yellowing (if yellowing and dying leaves is “climbing” up the plant from the bottom), especially in the vegetative stage before plant is making buds, you have a problem that you will need to fix as soon as possible.

You don’t want a nitrogen deficiency in the vegetative stage!

If you notice your lower cannabis leaves turning yellow in the vegetative stage or in the beginning part of the flowering stage, your plant may be experiencing a nitrogen deficiency which will need to be treated.

It is not good if your cannabis plant is showing signs of an advanced nitrogen deificiency while still in the vegetative stage. It’s normal to lose a few yellow leaves off the bottom of your plant here and there, especially with very big plants. But if you are losing a significant amount of yellow leaves, and the yellowing seems to be moving up the plant quickly, then you have a problem.

As a grower, you’re interested in how much nitrogen to give your plants at what time. The ratio of nitrogen to other nutrients has a huge effect on growth and bud formation.

Vegetative Stage – higher levels of Nitrogen (pretty much any plant food will do)

Most complete plant foods that you get at a gardening store contain high levels of nitrogen (N). These nutrient system tend to work well in the vegetative stage.

Some examples of cannabis-friendly one-part Vegetative nutrient systems…

Pretty much any complete plant food

Flowering Stage – lower levels of Nitrogen (use “Bloom” or Cactus nutrients)

It’s extra important to find a nutrient system with lower levels of nitrogen for the last part of your plant’s life. Many “Bloom” or “Flowering” style base nutrients are just the ticket.

Some examples of good one-part Flowering nutrient systems…

If you can’t order online and can’t find a good one-part base Bloom formula locally, you do have other choices. Though not an ideal choice, most Cactus plant foods will contain good nutrient ratios for growing cannabis during the budding stage. So in a pinch, you can use the cactus nutrients that can be found at most gardening stores.

The first cannabis plant pictured below is showing signs of nitrogen deficiency late in flowering; nitrogen deficiency in late flowering is completely normal and even desired. The last picture is an infographic about nitrogen and your marijuana plant.

It’s normal for plants to show signs of a nitrogen deficiency as the plant gets close to harvest. This is actually a good thing! Too much nitrogen can actually prevent proper budding, and can reduce the overall taste and smell of your plant. This is why all “bloom” and flowering nutrient formulas are relatively low in nitrogen.

Don’t worry about yellow leaves close to harvest! It’s normal to see a few Nitrogen-deficient leaves in the flowering stage. Nothing to worry about unless you see the yellowing leaves start climbing up the plant.

So don’t sweat it if you see your cannabis show some signs of nitrogen deficiency late in the flowering stage! Relatively low levels of nitrogen in the late flowering stage help promote proper cannabis bud development and will increase your yields!

Solution: You can find many pre-mixed nutrients from the store which contain nitrogen or you could use nitrate of soda or organic fertilizer which are both good sources of nitrogen. In fact almost all plant nutrients of any kind will include nitrogen. If you haven’t been providing any nutrient to your plants, try supplementing your regular nutrients with a bit more nitrogen and see if the plant starts recovering.

If you’ve already been using nutrients, then you probably don’t have a nitrogen deficiency. If you’re seeing the signs of spreading nitrogen deficiency even a week or two giving nitrogen to your plants through nutrients, then you need to figure out what else is causing the yellowing so you can stop it.

More About Nitrogen and Your Marijuana Plants

Sometimes you can get the signs of a cannabis nitrogen deficiency if the pH at the plant root zone is too low, even if the nitrogen is there. This is because when the pH at the roots is not right, your plant roots can’t properly absorb nutrients. If you aren’t sure about your root pH, learn more about pH & growing cannabis plants here.

Nitrogen is especially important during the vegetative stage of your cannabis plants. As your plants start flowering, they will need lower amounts of nitrogen.

Nitrogen is one of the 3 nutrients that is included in almost every kind of plant food.

When looking at plant nutrients, you’ll almost always see 3 numbers listed, like 3-12-6 or 5-10-5. These numbers represent the percentage of Nitrogen (N), Phosphorous (P) and Potassium (K) contained in the bottle. Just about all plant life on Earth needs these 3 elements to grow.

The 3 numbers on the front of plant nutrient bottles list the amount of Nitrogen, Phosphorus, and Potassium.

The very first number, “3” in the case of the picture to the right, always displays the proportion of nitrogen in this nutrient bottle compared to the other 2 nutrients (Phosphorus and Potassium respectively).

Nitrogen is in all plant nutrient formulations because it’s vital to plant processes.

Note: During the last few weeks before harvest, marijuana plants start pulling all the remaining nitrogen from her leaves as part of the bud-making process. This causes yellowing leaves starting towards the bottom of the plant. This is part of the natural flowering process and you don’t need to fight it. You may notice that marijuana leaves are yellowing in almost all pictures of marijuana plants with big buds that are close to harvest. You tend to get smaller yields from nitrogen-toxic plants with dark green leaves at harvest.

Remember: It’s Normal For Marijuana Leaves To Start Turning Yellow As Harvest Time Approaches

Occassionally a nitrogen toxicity is mistake for a deficiency. Could your plant actually be nitrogen toxic? (pictured below)

This picture shows a Nitrogen Toxicity

Plant Symptoms

  • Bronze or brown patches
  • Brown or slimy roots
  • Brown or yellow leaf tips/edges
  • Buds dying
  • Buds look odd
  • Bugs are visible
  • Curling or clawing leaves
  • Dark leaves
  • Drooping plant
  • Holes in leaves
  • Mold or powder
  • Pink or purple on leaves
  • Red stems
  • Shiny or smooth leaves
  • Spots or markings
  • Twisted growth
  • Webbing
  • Wilting leaves
  • Yellow between leaf veins
  • Yellow leaves

This page is part of our Plant Doctor series. You can use our tool to filter by symptom and help diagnose your plant.

A nitrogen deficiency causes the lower/older leaves of a cannabis plant to start yellowing, wilting, and dropping off on their own. Learn how to fix it.