Why Are My Leaves Turning Yellow / Brown / Red / Spotted?

Cannabis is an extremely difficult and highly sensitive plant to grow. This means that more often than not, you will end up doing something that will result in potential damage to the plant’s growth. And, that’s fine because you aren’t the only person who has messed things up. If you are sitting here being confused why my cannabis plant leaves are turning yellow, brown, or red, know for a fact that you aren’t the only person struggling with this issue.

More often than not, these are signs of deficiency in the plant that needs a quick fix. Sometimes, our yields don’t come out the way we expect them to and that is completely fine. You need to realize that not everything is sunshine and rainbows. Your leaves might end up losing color, curling in on themselves or they even might end up shedding before you have time to harvest them.

Whatever the issue be, know for a fact that you need to be mindful of the reasons and navigate around the issues by yourself. The process isn’t as hectic as you might think it is. However, knowing the reasons can help you act quickly and save your plant before it is beyond repair.

What is wrong with my Cannabis plant?

Cannabis is an extremely sensitive plant that requires optimal temperature, humidity, and pH settings to grow without any risks and damage. More often than not, this is where we fail. To figure out what is wrong with your plant, you need to check the signs of damage. What are the issues that you are facing with the plant?

Once you have the signs listed, you can then consult a professional for help. Generally, the reasons behind the damage to the plant are due to the following reasons. They include:

• pH imbalance
• Nutrient deficiency
• Watering issues
• Light burn
• Lack of light exposure
• Bud rot
• Heat stress or cold shock
• Insects or pests invasion

Whatever the issue is, all of them have the potential to make the leaves in the plant appear yellow, red, or rusty. For better understanding, let us walk you through each of these problems in detail:

• pH imbalance

As we have mentioned from the beginning, cannabis plants are extremely sensitive. Even the slightest change to the temperature, humidity or the pH of the growing medium and surroundings can end up damaging the plants for good.

Marijuana plants need to have a pH range between 6.3 and 6.8. If the medium is too acidic or too alkaline, it will end up turning the plant’s leaves into the unwarranted colours that we have mentioned in the title of the article.

So, if you are suspecting that the pH is the issue contributing to the change in colour of the leaves and the buds, you need to act quickly before it ends up doing some kind of permanent damage. Start by buying a pH meter to check the pH levels in the growing medium.

If you are certain that there is a pH drop or increase, the best way to check it is by checking the water that runs out of the growing medium. Once you have found the pH imbalance, the next thing you need to do is bring back the growing medium to the ideal pH balance. Adding chemicals can help with that process.

Also, make sure that you always make the pH adjustments after you have added the nutrients. This ensures that your plant soaks in the nutrients before the change in the pH levels again.

• Nutrient deficiency

More than changes in the pH level, nutrient deficiency is a contributing factor behind the changing colours in the leaves of the plant. Any kind of nutrient deficiency cannot just result in the drastic change in the color of the plant’s leaves but also affect other parts of the plant, including its quality and its growth.

Aside from changing colours, some of the other signs of nutrient deficiency in the cannabis plants include:

• Drooping leaves
• Leaves curling downwards

If you notice anything amiss with the cannabis plant, you need to act immediately before the plant dies. The process isn’t as hectic. You just need to refer to an official chart and appearance of the plant and check which kind of nutrient deficiency your cannabis plant has.

Generally, some of the common types of nutrient deficiency include:

• Nitrogen
• Phosphorus
• Potassium
• Magnesium
• Sulphur
• Manganese
• Iron

Once you know what kind of deficiency your plant has, you need to immediately supplement it with the needed nutrient to combat further damage.

• Watering issues

Moving on from the nutritional deficits, the last factor worth considering is the watering issues. They are very common, especially among beginners who don’t have a lot of knowledge surrounding plantation and harvesting.

Most of the time, you are either watering your plant very little or you are overdoing it. This problem is very easy to fix. The most common issue that planters deal with is overwatering. And, just because you have holes in the bottom of the planter doesn’t mean that you can water your plant a lot at a time.

The soil or growing medium can soak in a lot of moisture, resulting in damage. The best way to check whether it is the right time to water is by putting a finger into the soil. If the soil is too dry and makes it harder for you to put your knuckle in deep, it is time for you to water the plants. However, if that isn’t the case, you should refrain from watering.

• Temperature issues

Another common issue that can end up damaging your cannabis plant and turning the leaves brown or yellow is the sudden changes in the temperature. Cannabis, in general, requires very potent and controlled temperature and humidity settings in the room you are growing it in.

Sudden changes to temperatures – hot or cold, will end up affecting the viability of the plants and their quality too. Aside from temperature, you also need to ensure that your grow room has enough and ample air circulation around the room to further prevent risks of damage in the long run.

Also, the grow lights and their intensity can alter the temperatures that the plant is exposed to. The best way to check the intensity of the grow light is by placing your hand above the plant. If your hand starts to burn within 30 seconds, you need to push away the light from the plant or you need to reduce the intensity.

• Lack of light

While some grow lights end up altering the temperature of the grow room for the cannabis, too little light can also contribute to causing damage to the plant in the long run. If the light isn’t focused during the germination period, it will make the plant’s leaves curl in on itself. 

Lack of light in the room is also contributing to other risk factors like curling of the leaves, the transition of the colour of the leaves to light yellow, etc.

If that is the case, you need to introduce a higher intensity grow light in the room to reverse the damage.

Insect infestation

Insects and pests are common with any kind of plant. However, the problem is extremely evident with cannabis plants. If your plants are starting to rot away and you are experiencing issues with the colouration of the leaves, it is time for you to take immediate action.

You need to be vigilant of the surroundings and look out for possible signs of infestation. Even if you see one insect or pest creeping around, you need to get hold of them and get rid of it without any questions. The last thing you want is to cause any kind of permanent damage.

Also, check the plants for any infestation. If they are evident, you need to excise them before they start reproducing and infesting all the plants.

FAQs

Should I be worried if the cannabis leaves start changing colour?

A sudden change in the colour of the leaves and buds of a cannabis plant is a matter of concern. It can mean any of the above issues and this is where you need to step up. If you are witnessing any concerns from the above list, we’d recommend you take immediate action into correcting the issues.

Should I cut off the yellow and brown leaves?

Yes, most of the time, if your cannabis plant leaves are turning yellow or brown, it is best for you to trim them to ensure it doesn’t damage the healthy leaves.

How do flavonoids contribute to color in marijuana leaves?

The flavonoids are one of the most common reasons why the leaves have different kinds of colors in the first place. They react with the UV rays and block them during photosynthesis, leading to the distinctive color that you get on the leaves.

Anthoxanthins are the most common type of flavonoid that affects the color of the marijuana leaves. We’d recommend that you keep a check on the color change in the long run because it is not the flavonoids that make the color change all the time.

Does the temperature alter the color of the marijuana leaves?

The temperature plays one of the most notable roles in maintaining the color of the leaves in a cannabis plant. Typically, exposing the plant too cold for a longer period will reduce the green color of the leaves. This is a lot more common than you anticipate.

While it is not something you have to worry about much, we’d recommend avoiding prolonged cold exposure because it alters the chlorophyll levels in the plant.

Does the pH affect the color of the leaves?

Maintaining optimal pH is necessary for growing cannabis. The range will differ for hydroponics (5.5 to 6.5), soil (6.0 to 6.8), etc. Maintaining a neutral pH is ideal, especially if you are a beginner with not much information about the process.

The leaves can start showing red color if the pH goes under 5.5. So, if the leaves are turning red, chances are that the pH is going too low.

Does genetics play any role in the color of the leaves?

Some strains with blue and purple genetics often have a high level of anthocyanins in them. So, if your cannabis has blue and purple genetics, it is likely because of the genetics.

Conclusion

Growing cannabis takes a lot of effort on your part. If you are struggling to keep things in line and you are noticing something out of the blue, you must keep a check on the quality of the growing medium, the nutrition, or other associated factors that we have mentioned around here. If you can’t find the problem, consult a professional who can help.