Even experienced growers and beginners may encounter unexpected issues when cultivating cannabis. Whether you are growing your plants in coco coir, soil, or hydroponics, you may come across different problems that manifest as yellow stains on cannabis leaves. One of the most common issues is the appearance of yellow stains on the leaves. In this article, you will find information on the causes of yellowing leaves and how to prevent this problem from occurring.
Why do cannabis leaves turn yellow?
In order to address yellow leaves on marijuana plants, it is important to understand the reasons behind their appearance. Some of the common causes include:
Inappropriate pH levels
One of the main reasons for yellowing leaves is an unsuitable pH level of the nutrient solution. In soil, the pH level should be between 6 and 7, while in coco coir or hydroponics, it should range between 5.5 and 6.5. If the leaves start turning yellow, it could be a sign of an unfavorable pH level.
When pH levels are too high or too low, the plant may have difficulty absorbing the essential elements from the nutrient solution, leading to a lack of macro and micronutrients.
To address this issue, it is recommended to use a pH meter and cannabis fertilizers with a wider pH range that contains all the necessary microelements. Additionally, performing a root washing and restarting the fertilization with a more suitable solution for the growing media can help. Ultimately, creating the best possible environment for the plants is crucial.
Inappropriate temperature and humidity levels can also cause yellowing of the leaves. The ideal temperature for growing cannabis is between 10-28 ºC (50-82.4 ºF).
To prevent this problem, it is important to adjust the temperature by providing more light in the grow room or installing additional input-output fans in the grow tent. When growing outdoors, creating shade or using a greenhouse can be beneficial.
Excessive or inadequate irrigation can also cause yellowing of cannabis leaves. Some symptoms of improper irrigation include drooping of the plant, edema disorder due to excessive watering, thin and pale leaves due to insufficient watering, and root rot caused by overwatering.
Checking the moisture level of the substrate can help determine if irrigation is the problem. To address this issue, simply adjust the frequency and amount of water you provide to the plant.
A lack of nutrients can lead to nutritional deficiencies in cannabis plants and hinder their growth. On the other hand, over-fertilization can cause nutrient burn and result in leaf yellowing. It is important to remember that nitrogen, phosphorus, and potassium (NPK) are essential nutrients for plants.
Common nutrient problems include a lack of nitrogen, which can be seen as yellowing of the edges of the leaves that then spreads throughout. Over-fertilization may also result in bright leaves during the growing stage.
To prevent these problems, it is crucial to manage nutrient levels and understand the benefits that each nutrient provides for the plant.
Pests and fungi
Pests and fungal infections, such as septoria, can be detrimental to cannabis plants. Leaf yellowing can be an indicator of these diseases. Septoria infection, in particular, can occur at any stage of the plant’s life.
To treat these issues, pesticides or beneficial insects can be used to fight pests without harming the plant. When dealing with septoria, it is important to remove infected foliage and clean all tools after each use.
Tips to prevent cannabis leaves from turning yellow
Here are some useful tips to prevent the occurrence of yellow cannabis leaves:
- Choose a suitable cultivation method based on the strain’s resistance, whether indoor or outdoor.
- Adjust and regulate irrigation.
- Avoid exposing the plants to excessive heat and adjust the grow lights as necessary.
- Monitor and control temperature and humidity levels, ideally between 15-29 ºC (59-84.2 ºF) during the daytime.
- Avoid placing plants on cold surfaces to prevent root freezing and reduce cold resistance.
- Ensure proper nutrient supply.
- Regularly check the leaves for any signs of yellow stains, and address any deficiencies or excesses accordingly.
- If a deficiency is identified, provide the necessary substance to the plant. In the case of excess, perform a root wash and discontinue the use of fertilizers. When reintroducing fertilizers, follow the recommended schedule.
It is important to note that yellow leaves are a normal occurrence in cannabis plants during the advanced flowering period as they shed old leaves to save energy. Similarly, when performing a root wash, consider all the factors mentioned above to prevent these issues.
1. How do I know if my cannabis leaves are turning yellow due to pH levels?
If your cannabis leaves are turning yellow due to inappropriate pH levels, you may notice a lack of nutrient absorption and potential deficiencies in macro and micronutrients. Using a pH meter and fertilizers with wider pH range solutions can help address this issue.
2. What is the ideal temperature for growing cannabis?
The ideal temperature for growing cannabis is between 10-28 ºC (50-82.4 ºF). It is important to adjust the temperature and provide adequate light and ventilation to maintain optimal conditions for the plants.
3. How can I prevent yellow cannabis leaves?
To prevent yellow cannabis leaves, it is essential to establish a suitable grow method based on the strain’s resistance, adjust irrigation, manage temperature and humidity levels, provide proper nutrients, and regularly check the plants for any signs of yellowing. Addressing deficiencies or excesses promptly can help prevent further issues.
4. Can pests and fungi cause yellowing of cannabis leaves?
Yes, pests and fungal infections can cause yellowing of cannabis leaves. Common diseases such as septoria can be harmful to plants. To treat these issues, the use of pesticides or beneficial insects and proper sanitation practices, such as removing infected foliage, can be effective solutions.
5. Are yellow leaves normal during the flowering period?
Yes, it is normal for cannabis plants to have yellow leaves during the advanced flowering period. This is part of the natural process as the plant sheds old leaves to conserve energy. It is important to take this into account and differentiate it from other issues causing yellowing.