There are many reasons why cannabis leaves start curling, and in most cases, it’s an indication that something isn’t quite right. If you ignore the problem, your plants might die.
Here are a few of the most common causes of curled cannabis leaves and what you can do to help.
- Light/Heat Stress
Too much light can cause your plants’ leaves to curl. You can tell that this is happening because you’ll see the leaves twisting up towards the light source. They may also turn yellow. Heat stress can cause the same issue. It’s important to watch for high temperatures and adjust accordingly. Heat stress may also be caused by the proximity of your light source.
Move the plants further away from the lights or the heat source and observe them over the next few days to see if there are any improvements.
- Too Cold
In general, cannabis grows best between 70-85 degrees Fahrenheit. If the temperature drops below 50 degrees, curling leaves may be the first symptom that something’s off.
Exposing your plants to suboptimal temperatures for a long time could cause permanent damage. However, cooler temperatures may be used for short bursts during the late bloom to encourage different colorations.
- Excessive Nutrients
Cannabis plants need an exact balance of nutrients to thrive. Overloading with excessive nitrogen-rich nutrients results in curled, dark-colored leaves. Too much phosphorus or potassium during the flowering stage may also trigger curling.
Start feeding slowly and gradually increase your plants’ nutrients as they mature. Finding the exact balance may take time. If you suspect overfeeding at any point, use a water flush to lessen the impact and dilute the minerals’ potency.
- Overwatering
Overwatering causes the roots to become saturated, leading them to suffocate and turn brown. Cannabis plants need well-oxygenated roots to grow. If the condition is severe, the plant cells will puff up and cause the leaves to droop and curl.
That’s just one issue with waterlogged roots, however. The moist environment encourages root rot and other diseases. It’s important to keep the soil moist but not waterlogged; this is usually done on a schedule, with regular watering and proper drainage.
Check the moisture levels with a finger test before watering. If the soil feels dry, it’s time to give the plant a proper drink.
- Pests & Pathogens
Plant leaves that start to curl for no obvious reason may be affected by pests or pathogens. Inspect the plant thoroughly for signs of an infestation and take steps to treat it if necessary. You can also use a microscope to check for fungus gnats and other microscopic pests that can cause issues with your cannabis plant. Aphids, spider mites or the fungal disease powdery mildew are some of the most common culprits.
Insecticides work well against pests and fungicides are used for most diseases. Keep in mind that many of these products are toxic and will have an adverse effect on your plants if used incorrectly.
For pests infestations you might also be able to take a more natural approach using organic pesticides or even introducing beneficial insects.
Conclusion
Cannabis plants can exhibit a wide range of symptoms if something is wrong. Curled cannabis leaves are often the first sign of trouble and should be addressed as soon as possible. With that said, the causes for this issue vary greatly and finding out why your plant is struggling may take some time.
Keep a close eye on the plant and try to keep records as they will allow you to go back and identify potential problems more accurately. When in doubt, seeking help from an experienced grower may save you some time and money.
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