Why are Your Cannabis Leaves Curling? Find Causes and Solutions!

Posted on May 15 , 2024

Leaf curling is a very common problem during cannabis cultivation. But why do cannabis leaves curl? So, why do cannabis leaves curl? The answer lies not only in various environmental factors but in the complicated range of issues overall. Today, we will discuss what makes cannabis leaves curl and offer several reasonable solutions to make your plants energetic.

Environmental Factors

Environmental Factors

Temperature Issues

Cannabis plants are extremely sensitive to different temperatures. High heat will remove the moisture from the leaves, drying them out and causing them to curl. 

On the other side, low temperatures slow down the metabolism, leading to slow growth and curled leaves. The best temperature for cannabis ranges from 20 to 30°C (68-86°F). Natural summers recommend adding ventilation or cooling equipment to balance the heat, while in winters, plant growers use heaters to keep the plants warm.

Humidity Problems

Both high and low humidity levels affect cannabis negatively. High moisture can result in mold and fungal diseases that will make the leaves curl. Low moisture, in its turn, will make the leaves lose the moisture, dry out, and curl. The best condition is within 40-60%.

Light Issues

Light is needed for your cannabis growth, but too much or too little may cause the leaves to curl. Insufficient light makes the leaves weak and droopy and causes curling, while excessive light makes the curling edges scorched.

Make sure your plants receive 12-18 hours of the right light every day.You can use grow lights to ensure even and adequate lighting. However, it should be noted that the distance between the plant growth lights and the plants needs to be controlled, not too close or too far.

Nutritional Factors

Nutritional Factors

Nutrient Deficiency

 Cannabis needs balanced nutritional for those plants to stay healthy. The lack of key elements, such as nitrogen, potassium, and magnesium, leads to the curling change of the leaves’ color. To ensure a comprehensive supply of nutrients, make a routine of using high-quality plant fertilizers.


The excess fertilizer harms cannabis plants, making them curl and root burn and other effects. Follow the fertilizer instructions carefully to avoid over-fertilizing and flush the soil occasionally to prevent salt accumulation.

Pest and Disease Factors

pests and diseases.jpg

Common Diseases

Cannabis diseases are increasingly causing the curling of leaves, which include powdery mildew, root rot, among others. Powdery mildew appears as a white powdery substance on the leaf surface, affecting photosynthesis and destroying the entire plant through curling.

Root rot is caused by pathogens in the soil that lead to root decay but is easily transmitted to the whole plant’s health. Disease prevention includes keeping your environment clean, not over-watering, and using well-draining growing mediums. 

If diseases are discovered, use organic or chemical fungicides immediately.

Pest infestation

Pests such as spider mites and aphids excrete leaf sap, causing cannabis leaves to turn yellow, curl, and fall off. Spider mites produce the web structure on the ventral side of leaves, reducing the efficiency of photosynthesis. 

They can also move and hide under the leaf. Aphids appear on new leaves in anticipation, making them draw sap from cannabis foliage and causing deformation and curling. To avoid this, you must inspect plants regularly and maintain a clean growing environment and ventilation.

If pests are present, use biological control such as introducing predatory insects.

Watering issues

Over watering

Cannabis leaves curl due to over watering, a common issue. Over-watering starves roots of oxygen, causing root rot and impacting leaf wellness. Leaves start to curl and change color. 

To prevent over watering, utilize a dry-wet cycle, which means the soil surface should be completely dry before the next watering. Using pots with improved drainage, as well as choosing growing mediums with excellent drainage to improve soil drainage.

Water quality issues

Water quality can also affect the plant. When the water has a high salt incrustation, as well as when water has a high concentration of chlorine or other substances, root damage causes leaves to curl and turn yellow. 

Fill the pot with distilled water for 24 hours, filter, or utilize new tap water. Regularly check and maintain the pH of the water between 6.0-7.0. 

This will assist the plant in absorbing fertilizers better, reducing leaf problems.

There are many reasons why cannabis leaves curl, and the above are the more common causes and solutions. 

If you encounter any difficulties during the planting process, you can click on the dialogue box below to contact us at any time.

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