How to treat yellow cannabis leaves

These crops may experience some unexpected events for both expert growers and beginners. Regardless of if you’re growing your plants in coco coir, soil or hydroponics, there are multiple stains manifested on cannabis leaves. One of the most common problems that we may face while growing cannabis are the yellow stains on the leaves. Here you’ll find all the information to know their origin and how to prevent them from appearing

Why do cannabis leaves turn yellow?

To find out how to treat yellow leaves on our marijuana plants, we must know first the reasons that may cause them. Moreover, once the first signs of stress are noticed, Revive from Advanced Nutrients can be used. Some of them are:

PH levels

One of the main reasons for leaves turning yellow is inappropriate pH levels of the nutrient solution. These levels must be between 6 and 7 when growing in soil, while in coco coir or hydroponics, they can be between 5.5 and 65. If the leaves start turning yellow, this could be a sign of a non optimal pH level.

When pH levels are too low or too high, that can prevent the plant from absorbing the elements of the provided solution, that is to say, they will block the absorption of macro and micronutrients.

In order to solve this, it is recommended to use a pH meter and cannabis fertilizers with wider pH range solutions containing all the necessary microelements. We must perform a root washing and restart the fertilization with a most suitable solution for the growing media. However, the most important thing is to provide the plants with the best possible environment.

Temperature issues

An inappropriate temperature, as well as a wrong humidity level may turn yellow the leaves of your plants or strains. The most suitable temperature for growing cannabis ranges between 10-28 ºC (50-82.4 ºF).

To avoid this from happening, we must adjust the temperature, providing more light in the grow room if necessary or installing more input-output fans in the grow tent. When growing outdoors, we can place some structures to create shade or to work as a greenhouse.

Wrong irrigation

This is another common problem. An excessive or poor irrigation can also turn yellow your cannabis leaves. Some of the symptoms of a wrong irrigation are:

• Plant drooping.
• Edema disorder due to excessive irrigation.
• Thin and pale leaves due to poor irrigation.
• Root rot produced by over irrigation.

We can verify if we are facing an excessive or poor irrigation by checking if the substrate is too wet or too dried. To solve this, we must simply stop the irrigation or provide more water to the plant, respectively.

Fertilizer management

A lack of nutrients may produce nutritional deficiencies and interrupt the cannabis growth as this prevents the plants from performing their vital functions. Over fertilizing your plants may cause nutrients to be burnt and, consequently, leaf yellowing. Thus, it is important to remember that nitrogen, phosphorus and potassium (NPK) are essential nutrients for plants.

The most common nutrient problems are:

• A symptom of a lack of nitrogen that can be seen as it starts yellowing the edges of the leaves and then spreading this color all over them. However, if you see bright leaves during the growing stage, it may be due to over fertilization.

• The lack of potassium, the essential mineral to carry out photosynthesis and stoma function, causes your leaves to start turning yellow when there’s a deficiency of this compound. 

To avoid these problems, it is crucial to manage the nutrient levels, as well as knowing all the benefits that nutrients provide to every plant.

Pests and fungi

Pests and fungus infection such as septoria, may be very harmful for plants. To identify these diseases, we should simply observe the leaves, as this is where plages can be, to detect a possible leaf yellowing. The mentioned infection, septoria, can be harmful in any stage of the plant’s life.

To treat this disease, we can use pesticides or beneficial insects with which to fight any pest without harming the plant. When dealing with septoria, we must remove the infected foliage and clean all our tools after every use.

Tips to prevent cannabis leaves from turning yellow

Some useful tips are:

• Establish the chosen grow method knowing well the resistance of the strain either indoors and outdoors.
• Adapt and adjust the irrigation.
• Make sure that the plants haven’t too much heat, adjust the grow lights if necessary.
• Control the temperature and humidity levels: it should range between 15-29 ºC (59-84.2 ºF) during daytime.
• Don’t place your plants in cold surfaces as their roots may freeze and reduce their cold resistance.
• Provide the proper nutrients.
• Check daily the cannabis leaves in order to find yellow stains. If so, study a possible deficiency or excess.
• In case of deficiency, provide the plant with the substance it needs. In case of an excess, perform a root wash and stop using fertilizers. When it comes time to use it again, please follow the fertilizing schedule.

Despite what we have mentioned above, it must be taken into account that yellow leaves are normal in cannabis plants during the advanced flowering period as they come away from the old ones to save energy. It is the same way when it comes to performing a root wash. Thus, we must take all the factors mentioned above into account in order to prevent these problems.