Plant Cultivation

Cannabis Leaves Curling Up: All Possible Causes & Tested Solutions

causes and solutions to cannabis leaves curling up

Why Are My Cannabis Leaves Curling Up and How to Cure Quickly

You may encounter various issues when growing cannabis before harvesting healthy yields, say, yellowing leaves, powdery mildew, and one very common phenomenon - cannabis leaves curling up. If you notice the leaves of your cannabis curling up or down, chances are the plant is suffering from improper environmental conditions. In the following article, we will explore all possible reasons behind cannabis leaves curling up on edges and offer 5 working solutions to help you cure your cannabis.

Table of Contents

Why Are My Cannabis Leaves Curling Up

Cannabis leaves can curl up due to various reasons, and it is often not one single culprit but rather a combination of multiple ones. If you are able to identify underlying causes clearly, you can fix cannabis leaves curling up more effectively. 

Below we’ve gathered some of the most common causes of cannabis plant leaves curling up:

Light Stress and Heat

In case you are using any grow lights, say, HPS lights and LED grow lights, it’s likely the PPFD levels are excessively high for your cannabis growing. As a result, the leaves being exposed to strong light intensity get curled up to protect themselves. Or, you are placing the lights too close to your cannabis, so the heat your lights emit burns the leaves and causes cannabis leaves to curl inwards, especially the ones on the edges because they are generally closer to the light source.  

Pest Infestations 

Cannabis plants can attract a wide range of pests such as spider mites, aphids, thrips, and whiteflies, which all feed on the plant's sap. After sucking the sap from your leaves, these pests leave behind yellow spots on the leaves. Furthermore, pest infestations can cause a variety of symptoms, including droopy and twisted tops, blistered and glossy leaves, etc. 

Although it can be hard to distinguish which mites cause the problem, all pests cause damage to your cannabis leaves and stunt the growth of the plant for sure. 

Nutrient Deficiencies

Cannabis plants require a wealthy niche of nutrients to grow and thrive, and deficiencies in any of these nutrients can cause the cannabis to not grow the way you expect. For example, a deficiency in nitrogen can cause the leaves to turn yellow and end up curling up as they die, while a deficiency in potassium can cause the leaves to appear burned and curled up at the edges.

cannabis leaves curling up caused by nutrient deficiency

Nutrient Burn

In contrast to nutrient deficiency, overfeeding can also be a problem. Over-fertilized roots with excessive mineral content make it hard for your cannabis to remain optimized plant biochemistry. To name one example, if your cannabis is given excessive nitrogen-rich veg nutrients, the leaves will turn dark and present a claw-like structure. 

Incorrect pH Level

As a vital factor that affects the availability and uptake of nutrients by the plant, the pH level can easily affect your cannabis growth. If your plants are experiencing a low pH level, you can spot yellow-to-brown splotches on the upper leaves at first and finally curling up leaves at the end. For a high pH level, you may notice brown splotches taking over the whole leave. 

cannabis leaves curling up caused by low pH


Overwatering is a common mistake that beginners make when growing plants. Excessive watering swells the cell, making it impossible for the plants to absorb enough water and leading to drooping leaves that start to claw slightly. Additionally, the roots are suffering from inadequate aeration, which can negatively impact their health and function. For proper cannabis watering techniques, you may check this post: Ultimate Guide on Watering Cannabis: Best Time & How to

yellow to brown leaves

Extreme Temperatures

Cannabis plants are sensitive to temperature fluctuations, and extreme temperatures can cause the leaves to wrinkle and become crispy. High temperatures in the grow room (above 86°F) can cause the leaves to wilt, while cold conditions can cause upward curling on the leaf tips, which happens particularly in outdoor growing.

Improper Humidity Level

Cannabis requires a specific range of humidity levels to grow and thrive during each growth stage. High humidity levels can cause the leaves to curl up and create an environment for mold, while low humidity levels can cause the leaves to become dry and brittle. 

Wrong Soil 

If you prefer soil growing over hydroponics, the choice of soil matters. When choosing the ground for your cannabis, pay attention to the drainage, water retention, nitrogen content, and texture. For instance, soil that has bad drainage could result in waterlogging, which can lead to root rot, and therefore damage your cannabis growth. 

Genetic Natures

It’s not always your fault. As breeders continuously produce new cannabis strains, some of the new species come with different manifestations that include a curled leave. So, if you are planting any new cannabis mutations, perhaps one of their signatures is the clawing leaf and it’s actually not a big deal to you. 

How to Cure Cannabis Leaves Curling Up [5 Effective Methods]

Now you should know what causes cannabis leaves to curl up, the question now becomes how to fix this issue? In the following content, 5 major methods are included to help you cure cannabis leaves curling up on edges. Read on to find out how. 

Check for Bugs

Inspect your cannabis plants for signs of any pests. If you find pests, you can control the situation by spraying the plants with a solution of neem oil, insecticidal soap, or using an organic pesticide to eliminate them. 

Grow Room Temperature & Humidity Control

To control the grow room temp: 

Use a digital or analog thermometer to examine the grow temp and make sure the temperature for growing weed stays between 68-78°F (20-25°C). If the meter goes beyond that, you can control the temp with an inline fan for grow tent or air conditioner if available. 

Spider Farmer inline fan

To control the grow room humidity:

The humidity level is suggested to stay between 40-60%. For a low humidity level, you can raise humidity in a grow tent in multiple ways. For budget-efficient growers, use a professional plant humidifier such as Spider Farmer Cool Mist Humidifier for Plants. If you are more into ways without a humidifier, you can place wet towels and sponges to increase the humidity. If the grow room gets too moist, you should decrease the humidity then. 

However, if you are growing outdoors, the temperature and humidity can be more difficult to manage. Some growers just stop planting ween during the hottest days of the year to avoid extreme conditions. 

Maintain the Right Soil Moisture

There are various means to cure overwatering and avoid cannabis plant leaves curling up in the future. 

  • If you think the soil is already excessively watered, simply let it dry out for a few days. Then you can test the moisture level by pressing your fingers in the dirt. 
  • For less experienced cannabis growers, it’s better to underwater the seedlings rather than overwater them. Just be aware that it’s OK to leave the plants unwatered for a day or two.   
  • You can go for drip irrigation or use sprinklers with timers to better control the water amount. 
  • Use a soil moisture meter to make sure that the soil is moist but not waterlogged. 
  • Switch to a highly aerated growing container that allows more oxygen to penetrate the root mass. In this case, your cannabis root is less likely to be suffocated by overwatering. 

Moisture meter tester in soil

Adjust Nutrient Levels

For already overfertilized plants, you can rinse the roots with water to clear out excessive nutrients. Then, follow the common principles for adjusting nutrient levels in your cannabis to the optimal outcome, no matter whether it’s nutrient deficiency or overfertilization. 

  • It’s best to take organic nutrients such as soil or coco fiber instead of artificial ones. Although organic mediums release nutrients in a slower way, they can deliver the exact right amount that’s required by your plants and therefore prevent overfeeding or underfeeding. 
  • Slowly and gradually add nutrients to your cannabis as they mature. It’s not suggested to use strong nutrients at first just to shorten the growth process. 

Provide Proper Lighting

As mentioned earlier, intensive lighting can harm your weed. Compared with traditional HPS bulbs, LED grow lights can produce less heat, adjust light intensity, and are more energy efficient. To provide proper lighting for indoor growing, LED grow lights are good investments. 

The position of your grow lights is also worth thinking about - how far should led grow lights be from plants? Generally speaking, it’s a good idea to place the grow light at around 12 to 30 inches from your cannabis, however, bear in mind that as your plants grow, the height should be adjusted as well. 

Verdict on Cannabis Curling Up 

Why do cannabis leaves curl up? Bugs, overwatering, overfeeding, unsuitable temperature and humidity, and many other factors can be the reason. Regardless of which situation you are in, this post covers 5 working solutions to help you effectively fix cannabis leaves curling up. Don’t hesitate to leave a comment below if you have any questions or thoughts! 

FAQs about Cannabis Leaves Curling Up

  • Why are my cannabis leaves crispy and curling up?

The most common reason for cannabis leaves curling up is overwatering. Once the plants absorb too much water, cells rupture and cause the upper leaves on your cannabis being crispy and curling up. 

  • What does it mean when leaves curl up?

Leaves curling up on your cannabis means that your plant is suffering from various issues, including insect infestation, overwatering, nutrient deficiency, etc. It’s a sign of plants not growing properly. 

  • Why are my cannabis leaves curling like taco?

Heat stress and Calcium/Magnesium deficiency are two main factors that cause cannabis leaves to curl up like a taco. High temperatures can cause the leaves to curl up and turn yellow or brown at the edges, while a deficiency in Calcium or Magnesium can cause the leaves to become brittle and curl upwards like a taco.

  • How do you fix curling leaves?

It’s best to spot the reason for your curling leaves before hands-on fixing them. For overwatered cannabis, which is the most common cause, you can stop watering for a few days to let the soil drain out extra moisture. Then you can resume watering with drip irrigation to avoid overwatering again. 


About Ciki

Ciki has been navigating the digital world of SEO for over 3 years, applying her expertise originally in the software sector before turning her attention to indoor gardening. Merging her tech-savvy background with a passion for nature, Ciki offers a unique perspective on gardening, blending modern techniques with time-honored traditions.

2 thoughts on “Cannabis Leaves Curling Up: All Possible Causes & Tested Solutions

  1. Deborah A Townsend says:

    Thank you so much for the thorough answers! I am a new grower and find all my concerns here! I am not the only one.
    Deborah Townsend

    1. Ciki says:

      Thanks for your credits!

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