Cannabis Leaves: Understanding Yellowing and Brown Spots

Cannabis Leaves: Understanding Yellowing and Brown Spots

As cannabis growers, we know how disheartening it can be to see our precious plants develop yellow leaves or brown spots. These issues can hinder their growth and overall health. But fear not, because understanding the causes and implementing the right solutions can help restore your cannabis plants to their vibrant green state.

In this comprehensive guide, we will explore the various factors that can lead to yellowing leaves and brown spots on cannabis plants. We have carefully extracted the most relevant information from multiple reputable sources, ensuring that you receive accurate and up-to-date insights. So let's dive in and discover how to address these common problems in your cannabis garden.

Section 1: Why Cannabis Leaves Turn Yellow

Yellowing of cannabis leaves occurs when the chlorophyll, the green pigment responsible for photosynthesis, degrades. This can happen due to a variety of factors. Understanding these causes is crucial for effectively addressing the issue and ensuring the optimal health of your plants.

Watering Problems

Proper watering is essential for cannabis plants to thrive. Both overwatering and underwatering can result in yellow leaves. Overwatering can lead to oxygen deprivation in the roots, while underwatering can cause the leaves to appear thin and wilted. Finding the right balance and adjusting your watering practices accordingly is key to preventing yellowing due to watering problems.

Nutrient Deficiencies

Nutrient deficiencies, particularly nitrogen deficiency, can cause cannabis leaves to turn yellow. Nitrogen is vital for plant growth, especially for new leaves. A lack of nitrogen can cause upper leaves to draw nitrogen from lower leaves, resulting in yellowing and fading. Ensuring adequate nutrient supply, including nitrogen, is crucial for preventing this issue.

pH Imbalance

Maintaining the appropriate pH level of the water you use for watering cannabis plants is crucial. An incorrect pH level can hinder nutrient absorption, leading to yellowing leaves. Monitoring and adjusting the pH level within the recommended range can help maintain healthy foliage.

Lighting Issues

Proper lighting is essential for optimal plant growth. Excessive light exposure, especially when the lamps are too close to the plants, can cause yellowing and even burning of the upper leaves. On the other hand, insufficient light can result in yellowing of the lower leaves. Adjusting the distance and intensity of the light source can help mitigate these issues.

Temperature Problems

Extreme temperatures can also contribute to yellowing leaves. Heat stress, caused by temperatures above 28°C (80°F), can impede photosynthesis and lead to yellowing. Cold shock, on the other hand, occurs when temperatures drop too low, causing the plant to wither and turn yellow. Maintaining optimal temperature conditions is crucial for preventing these issues.


Pests can wreak havoc on cannabis plants, causing general weakness, yellowing, and visible signs of damage. Fungal flies, for example, can feed on the plant's roots, particularly in humid environments. Implementing preventive measures, such as limiting access to the plants and proper watering practices, can help prevent pest infestations and subsequent yellowing.

Section 2: Diagnosing Yellowing and Brown Spots

Accurately diagnosing the cause of yellowing or brown spots is crucial for implementing the appropriate solutions. By carefully observing the affected leaves and considering the accompanying symptoms, you can narrow down the potential causes and take targeted action.

Section 3: Solutions for Yellow Leaves

Once you have identified the cause of yellowing leaves, it's time to implement the necessary solutions. Here, we will explore various strategies and techniques to address specific issues and restore the health and vibrancy of your cannabis plants.

Correcting Watering Problems

To address yellowing due to watering problems, it's important to find the right balance. If you are overwatering, adjust your watering schedule and ensure proper drainage. Underwatering can be remedied by providing adequate water, ensuring each plant receives enough moisture.

Treating Nutrient Deficiencies

For yellowing caused by nutrient deficiencies, it's crucial to provide the necessary nutrients to the plants. Organic seaweed fertilizers can be beneficial in rectifying nutrient imbalances. Monitoring nutrient levels and adjusting feeding regimens accordingly can help prevent and treat deficiencies.

Balancing pH Levels

To address yellowing caused by pH imbalances, invest in a pH pen or opt for pH-perfect fertilizers that can auto-adjust the pH range. Flushing the growing medium with pure water and resuming feeding with a properly balanced solution can help restore pH levels.

Adjusting Lighting Conditions

If yellowing is caused by lighting issues, adjust the distance between the lamps and the plants. Moving the light source further away can prevent burning and yellowing of the upper leaves. Similarly, ensuring adequate light exposure for the lower leaves can prevent yellowing due to insufficient lighting.

Managing Temperature

Maintaining optimal temperature conditions is crucial to prevent yellowing due to heat stress or cold shock. Ensure proper air circulation and consider providing temporary shade if necessary to prevent overheating. Protecting the plants from extreme cold is also essential for their overall health.

Addressing Pest Infestations

If yellowing is caused by pests, it's important to take immediate action to eliminate them. Applying insecticides specifically designed for cannabis plants can help eradicate pests and prevent further damage. Implementing preventive measures, such as proper hygiene and limiting access to the plants, can help minimize the risk of infestations.

Section 4: Trimming Yellow Leaves

In some cases, trimming yellow leaves can improve the overall appearance of the plant and redirect its energy towards healthy growth. However, it's important to consider the plant's stage of growth and the extent of yellowing before deciding to trim. Young plants may benefit from leaving the yellow leaves intact, while more mature plants can tolerate some pruning.


According to experts who write for us on cannabis and CBD, yellowing leaves and brown spots on cannabis plants can be distressing, but with proper diagnosis and targeted solutions, you can address these issues effectively. By understanding the potential causes and implementing the appropriate strategies, you can restore the health and vitality of your cannabis garden. Remember to monitor your plants closely, make necessary adjustments, and provide the optimal growing conditions for your cannabis plants to thrive.

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