Cannabis Leaf Curl Symptoms and Remedies

Cannabis cultivation can be tricky. Throughout your marijuana’s growth stages, you’re going to have to keep a close eye on your plants to ensure that they’re growing as healthily and happily as possible. If they start to exhibit signs of cannabis leaf curl, for example, you know that something’s wrong.

But, what exactly does cannabis leaf curl mean, and how can you fix it if it starts to happen? Below, we’re covering everything there is to know about cannabis leaf curl symptoms, remedies, and more. Let’s get started.

Understanding Leaf Curling

First, let’s address the basics: cannabis leaf curling is a condition where the leaves of a marijuana plant exhibit abnormal curling or twisting. This can manifest as upward or downward curling of the leaf edges, as well as twisting or distortion of the leaf structure itself. Cannabis leaf curling symptoms can vary, but essentially, you’ll look at your plants and notice their leaves growing in abnormal, atypical ways.

The curling may occur along the edges of the leaves or the leaf tips, causing them to roll upward or downward, or it may affect the entire leaf. Affected leaves may also become brittle, leathery, or exhibit other changes in texture compared to healthy leaves. You’ll likely notice these curled leaves primarily within the vegetative stage, but they may also be apparent during the flowering stage. 

Sometimes, leaf curling may be accompanied by changes in leaf color, such as yellowing, browning, or spotting. Then, in severe cases, leaf curling can impact the overall growth and development of the cannabis plant, leading to sick plants and a potentially unsuccessful yield.

Causes of Leaf Curling

Unfortunately, there are a lot of reasons why your marijuana plants start experiencing leaf curl if you’re not careful—or if you’re a beginner grower.

Here are some of the main causes of leaf curling during cannabis cultivation.

Environmental Factors

The environment surrounding your growing cannabis plants will directly impact their health, potency, and overall success. If you’re not keeping your plants in the right conditions, there’s a chance you will start to notice leaves curling. This can be due to several environmental factors, but some of the main ones include incorrect temperatures, improper humidity levels, and light stress.

Extreme temperatures, either too high or too low, can stress cannabis plants and lead to leaf curling. Heat stress can cause dehydration and leaf curling, while cold temperatures can inhibit nutrient uptake and metabolism, also leading to curling. Improper humidity levels, too, can affect transpiration and water uptake in cannabis plants, causing leaves to curl. Essentially, strong humidity can promote fungal diseases and waterlogging of the roots, while low humidity can lead to excessive water loss through transpiration.

Finally, excessive grow light intensity can cause photoinhibition and leaf curling in cannabis plants, especially if the plants are not adequately acclimated to high light levels. On the flip side, insufficient light can lead to stretching and weak growth, which may also result in leaf curling. So, if you start to notice cannabis leaf curl in your plants, it’s important to double-check your grow space’s temperatures, humidity levels, and light source intensity to ensure they are where they should be.

Watering & Nutrient Issues

If your environmental conditions seem to be correct, then you might have a watering or nutrient issue on your hands.

Both overwatering and underwatering can stress cannabis plants and lead to leaf curling, so you have to be extra cognizant. Using excess water for your marijuana plants can result in waterlogged soil and root rot, while underwatering can cause dehydration and nutrient imbalances.

Speaking of nutrient imbalances, your cannabis leaf curl may be a sign of deficiencies or nutrient burn. Imbalances or deficiencies in essential nutrients like nitrogen, potassium, magnesium, or calcium, can lead to leaf curling in cannabis plants. Incorrect soil pH levels can also affect nutrient availability and uptake in cannabis plants, leading to leaf curling. Generally, cannabis plants prefer slightly acidic to neutral soil pH (around 6.0 to 7.0), so make sure your plants are getting the amounts that they need for healthy growth. Following a strict watering schedule can help with this, too. 

Pests & Diseases

Other primary causes of cannabis leaf curl are pests and diseases. These invasive factors can easily affect the health of your plants in various ways, including their ability to produce healthy plant growth and uncurled leaves.

There are various common pests such as spider mites, fungus gnats, and aphids that feed on the plant’s tissues—including the leaves. Their feeding can cause damage to the leaf tissue, creating the distortion of leaf shape and the curling of leaves. Pests that feed by sucking sap from the plant, such as aphids and spider mites, can cause leaf curling by depleting the plant’s water and nutrient reserves. This can lead to dehydration and wilting of the leaves, which will also result in curling and distortion.

Fungal, bacterial, and viral pathogens can infect cannabis plants and cause diseases that manifest as leaf curling among other symptoms. For example, fungal diseases can colonize the leaf surfaces and affect normal leaf development, leading to curling and distortion. Bacterial and viral diseases can also cause necrosis and tissue damage, resulting in leaf curling. Thus, managing pests and diseases effectively through preventive measures such as sanitation practices and the use of integrated pest management (IPM) strategies can help lower the risk of leaf curling in your precious cannabis plants.

Genetics

Finally, a straightforward albeit frustrating cause of cannabis leaf curl is genetics. Simply put, some cannabis strains are more predisposed to curling than others, and these traits could be the result of selective breeding for specific characteristics such as leaf shape, size, or structure. Certain genetic lineages may naturally produce leaves that tend to curl or twist under certain environmental conditions, too.

This is why it’s crucial to research the strains you’re interested in first before buying. Here at Growers Choice Seeds, we offer a huge selection of high-quality cannabis seeds that are not only adaptable, but they’re hardy and resistant. Typically, indica-dominant strains like Purple Punch that have broad, thick leaves tend to be more resistant to curling; landrace strains like Colombian Gold, too, tend to have hardy genetics that is good for resisting curling and growing happy, healthy plants.

Remedies and Preventative Measures for Cannabis Leaf Curl

Cannabis leaf curl may sound a little scary; thankfully, there are plenty of remedies and preventive measures you can take to help nurse your plants back to health—and grow uncurled leaves. Here are some great remedies for cannabis leaf curl:

• Optimize environmental conditions: Make sure you’re maintaining stable temperature and humidity levels within the appropriate range for cannabis cultivation. Also, ensure proper air circulation and ventilation to prevent stagnant air and humidity buildup, and avoid excessive light exposure that can stress the plants.
• Nutrient management: It’s important to conduct regular soil testing to monitor nutrient levels and pH, adjusting fertilization accordingly to prevent deficiencies or imbalances. Try to use high-quality, balanced fertilizers formulated for cannabis cultivation to provide essential nutrients.
• Pest and disease control: If you’re having trouble with pests, Implement integrated pest management (IPM) practices, including regular scouting, physical removal of pests, and the use of biological controls or low-toxicity pesticides when necessary. It’s important to practice good sanitation to remove plant debris and minimize conditions conducive to pest and disease development.
• Genetic selection: It’s worth it to choose cannabis strains known for their resilience to leaf curling or other environmental stressors. Select stable seeds with well-adapted genetics such as auto-flower strains like White Widow or photoperiods like Blue Dream.

Understanding Cannabis Plant Health With Growers Choice Seeds

Here at Growers Choice Seeds, we understand how tricky cultivating cannabis can be. After all, these plants can be a little bit delicate, especially depending on the strains you choose to grow. Thankfully, as long as you have proper knowledge and awareness of conditions like cannabis leaf curl, you can better take care of your plants and correctly treat them if problems arise.

Whether you’re looking for a great beginner strain like Northern Lights or something more advanced like Headband, Growers Choice Seeds has the perfect selection for your cannabis garden. And, not only that, but we also offer plenty of resources, including growing and germination guides, to help you every step of the way.

FAQ

Should I prune affected leaves when dealing with leaf curl?

When it comes to pruning, it depends on the severity and cause of the leaf curl. If the curling is due to a pest infestation, disease, or irreversible damage, pruning affected leaves may help prevent further spread and promote the plant’s overall health.

However, if the curling is minor and caused by temporary environmental stress, it may be best to leave the leaves intact, as they may recover once you adjust the actual stressor. So, make sure you pinpoint the cause of curling before deciding to prune.

How can I prevent cannabis leaf curl in future growth?

There are several things you can do to prevent cannabis leaf curl in future growth. Here are some great preventative measures to take:

• Maintain stable environmental conditions, including temperature, humidity, light intensity, and airflow.
• Ensure proper watering practices by avoiding overwatering or underwatering.
• Monitor and maintain balanced nutrient levels, adjusting fertilization as needed based on soil testing.
• Implement integrated pest management (IPM) strategies to prevent and control pest infestations. Conduct regular inspections to ensure your plants aren’t being affected by bugs or other pests. 
• Select resilient cannabis strains with stable genetics and disease resistance.
• Practice good sanitation and hygiene to prevent the buildup of pests, diseases, and plant debris. Try using insecticidal soap. 

How can I differentiate between nutrient deficiencies and leaf curl?

Differentiating between nutrient deficiencies and leaf curl can be challenging, but they do present slightly different symptoms. Nutrient deficiencies, for example, often cause specific symptoms such as yellowing, browning, or chlorosis of the marijuana leaves, along with stunted growth or necrosis.

Curly leaves due to nutrient deficiencies may occur along with other symptoms such as leaf discoloration or distortion. Thus, conducting a soil test and closely monitoring plant health can help identify nutrient deficiencies and distinguish them from other causes of leaf curling.

Can plants recover from leaf curl?

Yes, weed plants can recover from leaf curling, especially if the underlying cause is identified and addressed promptly!

Once the stressors or imbalances affecting the plant are corrected, new growth may emerge with healthier leaves. However, the extent of recovery depends on factors such as the severity of the damage, the plant’s overall health, and how quickly corrective actions are taken.

In some cases, especially if the curling is severe or chronic, affected weed leaves may not fully recover, but the plant can still continue to grow and produce new foliage. So, not all hope is lost for cannabis growers if they do experience cannabis leaf curl during a growing season.