Does your cannabis plant have yellow leaves? We explain to you the reason and the solution

Reading Time 5 minutes
Image of a yellow marijuana leaf between question marks, on a green plant background
Image of a yellow marijuana leaf between question marks, on a green plant background


Do you have cannabis plants and have you found some yellow leaves on them? This is fairly common in cannabis growing, so you’re not witnessing an exception, nor is it hopeless.

In general, this is not a symptom of something particularly serious, so when it happens it should not be considered a big deal. What you should do is try to detect the cause to definitively eradicate the problem, so today we will show you the main reasons that can justify its color.



🚀 Do you know the most common causes of yellow leaves on your cannabis plant ?



Excess of watering

If a cannabis plant is overwatered, there may be a lack of oxygenation in the roots of the plants, a situation caused by waterlogging in the substrate. Something as simple as this, can make the leaves have a yellow color and is usually one of the main causes. If the substrate has a permanent wet look and the new leaves at the top show up yellow, this is a sign that over watering is the cause.


Lack of Nitrogen

If the soil that is being used to grow the plants is not of the necessary quality, it is possible that a lack of Iron or Nitrogen will be detected and this will result in the production of yellow leaves. This problem is not unsolvable and the situation can be improved with something as simple as adding a supplement to the substrate, something like the vitamin complexes that we take when our body has this type of deficiency.

Another problem that can lead to this deficiency is the abuse of fertilizers in the substrates, which somehow choke them and prevent the correct absorption of the nutrients needed for their development. If the lack of Nitrogen or Iron comes from this problem, the roots would have to be washed and better control the amounts from that moment on.


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Advanced flowering in cannabis plants

During the flowering process, plants build buds and it is common for them to produce yellow leaves and these to fall off. These are usually the oldest parts of the plant and are naturally removed to spend those energies on developing these new buds.

This phase is completely natural and healthy for the growth of cannabis plants. Moreover, if this does not occur it may be due to an excess of fertilizer in the soil that is interfering with the normal development of its cycles. If these yellow leaves do not fall off naturally, the optimal solution is to prune them to encourage the process.


Lack of light

For cannabis plants to grow properly they will need their dose of light, as is the case with all types of vegetation. If they don’t get enough, the leaves will most likely start to turn yellow and also fall off the plant. This is because the process of photosynthesis can not be completed without the necessary amount of light, which results in some plants withered and not very vigorous.


Lack of Potassium

Potassium deficiency is one of the factors that can produce the appearance of yellow leaves on marijuana plants. In this case two different scenarios can be found:

  • When it happens during the first month of flowering.
  • When it happens during the last weeks of flowering.


*During the first month of flowering

It is possible to find yellow leaves in the first month of flowering of cannabis plants and this may be due to a lack of Potassium. At this point you will have a simple solution since it will be enough to add a specific fertilizer in the water with which the crop is irrigated. You can also include a small amount of guano in the soil and the problem will be solved in a short time.


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*During the last weeks of flowering

Finding yellow leaves on marijuana plants during the last weeks of the flowering phase can be quite common. This phenomenon occurs because the plant is using all its resources and nutrients to fatten the buds and does not have enough energy for the rest, so it gets rid of the unnecessary leaves. To solve this problem it will not be necessary to add any type of fertilizer since it is part of the natural process of their evolution. Ideally, you should let it continue its process without worrying too much.

As a general rule, cannabis plants go through different processes throughout their growth and the appearance of yellow leaves can be a symptom of a deficiency or a problem, as long as it is manifested in an early phase. It is important to find a solution if this is due to an excess of water, fertilizer or a lack of essential nutrients. But it should never be a reason for warning if the plant is already forming the buds and removing the leaves to use all its resources.

If this symptom takes place in your crops, you should not give it up or consider that the plants are unusable, as there is usually a simple solution based on the use of fertilizers, light control or irrigation dosage.


Infographics on yellow leaves on a marijuana plant
Infographics on yellow leaves on a marijuana plant



👾 Conclusion


Cannabis plants may occasionally have yellow leaves, but this should not be a warning sign. Usually it is caused by small setbacks that have an easy solution.

A common cause is overwatering, which can choke the substrate and prevent it from acquiring the nutrients needed for growth. Another common reason is a lack of Nitrogen or Iron, which is usually caused by an excess of fertilizer and has a very simple solution.

If the plants do not have enough light they could be affected when completing their process of photosynthesis and result in a series of yellow and not very vigorous leaves.

In an advanced flowering in cannabis plants, these will have yellow leaves to favor the growth of the buds, and this is another common reason. Finally, a lack of Potassium could produce this phenomenon, although it will be fixed by adding a specific type of fertilizer to the plant.

As you can see, yellow leaves on cannabis plants are a common problem that has an easier solution than you might think.

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Alan Martínez Benito
Alan Martínez Benito
CEO of Pev Grow, expert grower with more than 20 years of experience.
In constant struggle for the regulation of cannabis, mainly in the medicinal field.
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  1. Avatar for Luís Miguel Pereira antas

    Hello I’m from Portugal lisboa my name is Miguel antas and I have 6 plants 3 critical from royalqueenseedsbank and 3 triple G, all the plants have issues, and the r on cycle 12/12 from day 1 of january and the pistils they r so small and no buds yet

    • Avatar for Juanma de

      Hello Luis,
      It is very rare what you say, if you want you can send us a photo to our email and we will advise you better:

  2. Avatar for Griff jeske

    For real? Is that so. Wow i did not learn that in the books i read, well one out of four for this advanced grower is garbage. That’s why my weed is always one step away from going in the garbage it seems with a mistake. These this are a must to know when trying to master the growth of such a powerful plant as the cannabis plant.