Why Are My Marijuana Leaves Turning Yellow?

It can be really disappointing to suddenly see your marijuana leaves turning yellow, even after taking great care of them. Under normal circumstances, they should be green and look very lively. However, there are many reasons why the leaves may lose their glow. If you are worrying about the quality of your production, go through this article to find the possible cause and their solutions.

Raising cannabis may take quite an effort. It involves watering, providing nutrition, managing light, trimming, and whatnot. Of course, there is the additional pest removal, too. Even after all these, the glow on the leaves may be absent. In that case, know that there are some issues involving your cultivation.

The weed leaves turn yellow because of the decrease of chlorophyll (usually green chlorophyll). The name of this condition is Chlorosis. In this article, we explained the various reasons why your cannabis plants may be facing this and how you can cure them.

Underwatering or Overwatering

Like many other plants, Sativa and Indica require a proper watering cycle for their growth. However, many people either neglect to water them enough or end up overwatering. Both are harmful to the tree and can cause Chlorosis. So, a proper balance of wet and dry cycles is a must.

  • Solution 1: One of the most common ways many beginner marijuana farmers solve this issue is by lifting the container and comparing their weight between when they are dry and when they are hydrated enough. However, if you gain enough experience in this job, you can probably tell which plants are underwatered and which are overwatered.
  • Solution 2: If you look at the leaves carefully, you will find them frail and thinner with a lack of water or droopy and slightly inflated with too much water. Another solution to maintain proper watering is to check the drainage system. Ensure that your marijuana pots have drain holes for excess water to escape.

Nutrient Deficiency

Nutrient deficiency is a common condition for marijuana plants for beginner cultivators. Trees get their required nutrients from their food. Without enough of it, they can’t produce enough energy. Now, you may need to add extra nutrients occasionally to keep the NPK ratio in balance.

The NPK ratio indicates the ratio between Nitrogen, Phosphorus, and Potassium in the plant. Here, most nutrient deficiency happens because of a lack of nitrogen or iron. With their absence, the leaves can’t thrive and grow and turn yellowish.


  • You can identify nutrient deficiency by checking the NPK ratio on the labels of the plant food bottles.
  • Another way to identify it is to check whether the yellowing is near the base of the plant. If so, it is probably nutrient deficiency.
  • You may also notice yellowing in the leave’s veins, which indicates a magnesium deficiency.


  • If there is a lack of nitrogen, which is the most common, you can take a fertilizer solution with a high nitrogen content and mix it with the water before you water your plants.
  • If the issue is a lack of iron, the best option is foliar feeding with chelated iron.
  • If it is a magnesium deficiency, add magnesium solutions.
  • The yellowing may also happen because of a high amount of nutrients. In that case, you can clean the root system by flushing it with water. Then, use half-dose of the usual fertilizer you use to balance the nutrients.

Other Factors to Remember:

  • When adding fertilizers to your plants with lack of nutrients, choose one with a higher number. They will usually be labeled with Grow. Meanwhile, the ones with a lower number will have labels like Flowering.
  • Check the nutrient level of the plants only after you have checked the pH balance, lighting, and watering amounts.
  • Do remember that many people mistake a pH imbalance for nutrient deficiency. If you make the wrong diagnosis and act on it, it may harm the trees.

Pest Infestations

It is not difficult to identify a pest infestation in your cannabis garden. Many novice farmers may carelessly bring pests with them into the growing space. And the worst thing is that pest infestation for cannabis plants is really tough to get rid of once it starts. Using any solution or pest control may also harm the plants. So, it is better to stay careful from the beginning.

Identification: Aside from the usual yellowing of the leaves, a pest infestation will result in bite marks and spots. You may also notice tail signs. Meanwhile, damaged roots may indicate a fungus infestation.


  • Always wash your hands and use a different cloth when entering your cannabis garden to avoid bringing outside pests. Also, cover your hair.
  • Do not transfer any plant from the outside into the garden or greenhouse.
  • Never let any pet enter the grow room or even come near it. Add fences and stuff around.
  • If you notice infestations by fungus gnats, try limiting watering until it becomes mandatory for the plant, like when the top part of the soil gets dry. Without sufficient water, the fungus can’t reproduce.

Environmental Factors

Different environmental factors can directly or indirectly affect the growth of marijuana plants. Let’s explain some of them below-

why are my marijuana leaves turning yellow

Absence of Adequate Lighting

As many of us know, trees need CO2 and light to complete their photosynthesis process using their leaves. It gives them the necessary energy, like how we get food. However, if your cannabis plants are not getting the proper lighting, they will start turning yellow. The lack of energy also hinders their growth.

Solution: The solution to this issue can be using a light with a higher intensity. For example, you can replace your farm’s incandescent or halogen lights with HID (High-Intensity Discharge). They emit a higher lumen in comparison. LED lights may also work.

Alternatively, you can try bringing the hanging lights down to let the leaves get more light.

Nutrient Lockout or pH Imbalance

One of the first steps you must take when diagnosing your marijuana plants is to measure their pH. The potential hydrogen of the soil mix must remain between 6 and 7. Meanwhile, it must be 5.5 to 6.2 in the water. Anything higher or lower than these limits can cause an imbalance.

This condition is known as nutrient lockout because it can cause the trees to be unable to absorb nutrients. As a result, as you add more nutrients, they may become over-abundant, but your plant may not be receiving them. So, it can’t cook the energy it needs.

Solution: Once you measure the pH, add any pH up or down solutions that the soil or water needs. Make sure to add a bit and measure again before adding more.

Too High or Low Temperature

The necessary temperature range for marijuana plants is 70 to 80° F. If it is too hot or too cold, the leaves may start to curl up, lose their color, and even fall.


  • If the temperature is too high, you can use a fan to reduce the heat.
  • If the temperature is too cold, install root insulation to control the heating.
  • If the floor or ground is too cold, you may place the plant container on stools or someplace slightly higher.

Excessive Humidity

Too high or low humidity may cause the water to get dull or discolored. Because of this, you need to plant the cannabis at the right time of the year when the humidity is just proper.

Solution: Find which month of the year is best for planting cannabis plants in your area. For most states in the USA, it is March, when the winter ends and the humidity hasn’t increased too much. But avoid planting them around August, when the humidity is usually the highest.

Tips for Creating Suitable Growing Conditions for Healthy Plants

The first and foremost step you need to take while creating a suitable growing situation for your healthy marijuana plants is to research the different factors. Such as-

  • Learn to keep a watering balance to avoid under or overwatering your plants.
  • Make sure not to bring outside pests inside the sanitary growing space accidentally.
  • Plant the seeds at the right time of the year.
  • Provide the marijuana plants with enough nutrients and check their NPK and pH levels occasionally to keep both balanced.
  • In order to establish a perfect temperature, use fanning and insulations as necessary.
  • If there is not enough light in the environment, install artificial lighting like HID.


There are so many reasons why the leaves of marijuana plants can turn yellow. Many of these causes are easy to deal with. You may need to be careful about keeping things in balance. Whether you water them right, add the correct fertilizers, and arrange ample lighting may determine the growth and glow of your lovely plants.

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Nazmul Nahid

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