Why do cannabis leaves curl? You’ll see it here.

• We delve deeply into the causes of leaf curling in cannabis, from water and thermal stress to nutritional imbalances. We offer practical solutions, prevention tips, and specific care for growers, ensuring the well-being of your plants.
• How to prevent cannabis pests
• Different types of stress in cannabis

Alan Martínez Benito

CEO of Pev Grow, expert grower with more than 20 years of experience.
In constant struggle for the regulation of cannabis, mainly in the medicinal field.
26-04-2024 08:00:00 - Updated: 26 April, 2024

Growing cannabis is an art and a science that combines botanical knowledge with careful observation and adaptation to the needs of the plants. One of the most visible and concerning problems for growers is the curling of cannabis plant leaves, a symptom that can have multiple causes and solutions. This article dives into the depths of leaf curling, offering a detailed approach to its prevention and treatment, and as I don’t want to waste a minute, let’s start looking at the possible causes.

✅ Water Stress

 

Water is vital for all plant functions, from photosynthesis to nutrition. Inadequate watering, either by excess or deficit, can cause stress in plants, often manifesting in leaf curling.

• Overwatering: Constantly moist soils deprive roots of oxygen, which can lead to curling and yellowing of the leaves.
• Underwatering: Dehydrated plants will try to minimize water loss, resulting in upward curled leaves.

Tips for Effective Watering

• Use a soil moisture meter to determine the need for water.
• Establish a watering schedule based on the growth stage and environmental conditions.

🔥 Thermal Stress

Extreme temperatures, both high and low, can cause leaves to curl as a protection mechanism.

• High Temperatures: Leaves may curl up to reduce the surface exposed to heat.
• Low Temperatures: Cold can cause leaves to curl and harden.

Temperature Management

• Maintain the growing environment within an optimal range of 22-28°C during the day and not less than 18°C at night.
• Use fans, air conditioners, or heaters as needed to stabilize the temperature.

✨ Light Stress

Too much light can be harmful to plants, and this can occur for 2 reasons, either by having a too powerful light source or by having the light too close to the plants. However, it is the simplest problem to solve, as it is enough to move the light away so that the curling leaves stop doing so within days. If you want, you can also use a luxmeter to determine the amount of light your plants receive.

👾 Nutritional Imbalance

Both nutrient deficiency and excess can cause problems in the leaves. “Nutrient burn” is a common problem that causes the tips of the leaves to curl and turn brown.

Nutrient Adjustment

• Perform soil or growing medium tests to adjust fertilization and use an EC meter to check the amount of nutrients you are giving to the plants.
• Follow dosing recommendations and avoid excess fertilizers.

Specific Solutions for Common Problems

• Leaf Tips Curling and Turning Brown: Reduce nutrient concentration and increase watering slightly to help “flush” excess salts from the soil.
• Young Plants with Curling Leaves: Ensure that seedlings are not exposed to cold drafts or too intense light.

⭐ Prevention and Care

• Regular Monitoring: Inspect your plants daily for early signs of stress.
• Controlled Environment: Use tools like thermometers, hygrometers, and pH meters to maintain optimal conditions.
• Adaptation and Learning: Keep a record of your growing practices to learn from past experiences and continuously improve.

🎯 Conclusions

As you may have seen, the causes of cannabis leaf curling can be varied, but fortunately, all have a solution, and if you perceive the problem when it starts to occur, you won’t have much trouble solving it. One of the most common mistakes has to do with watering, as it can be bad both by excess and by deficit, so I thought it convenient to leave you here this other article that explains how to water marijuana correctly, as it may resolve some doubts.