Introduction
What does it mean when cannabis leaves are curling? Your cannabis plant cannot scream for help, but it will give you signs that something is wrong with it. Every weed grower might have experienced these issues where the plant got distressed due to environmental or genetic stress. It may include yellowing of leaves, clawing or curling of leaves, or dry brittle leaves. Where curling or leaves is the most common issue among indoor cannabis growers. However, it is curable, but beginners don’t know what to do. Cannabis leaves curling can be caused by a range of issues, including nutrient deficiencies, overwatering, pests, or environmental stress, affecting plant health.
So, whether you are a novice or a pro-marijuana cultivator, we are here to give you all the reasons why your cannabis leaves are curling up or down and what to do to prevent this issue and correct it. Stay tuned!
Understanding Cannabis Leaves Curling
Before delving into solutions, it’s essential to understand why cannabis leaves curl and what it signifies. Cannabis leaves curling typically occurs as a defensive mechanism in response to environmental stressors such as under-watering, over-watering, nutrient deficiencies, heat stress, or pest infestation. Recognizing these stressors is crucial for effectively addressing cannabis leaves curling and restoring plant health. By identifying the underlying causes of cannabis leaves curling, growers can implement appropriate measures to mitigate stressors and promote optimal growth and development. Let’s explore the common stressors that lead to leaves curling and strategies to address them for healthier cannabis plants.
Here are some general guidelines regarding what issues your cannabis plant might have ( however, we will discuss the whole matter in the content)
- Leaf curling down, no yellow: under-watering
- Leaf curling down and yellowing: over-watering
- Leaf curling up: heat stress
- Leaf curling in a deformed way: pests or diseases
- Old leaves curling with patchy yellow veins: Magnesium deficiency
- New leaves curling with green veins and yellow patches: Manganese deficiency
Cannabis leaves curling signals underlying issues that require prompt attention to prevent further damage. Early detection is crucial as it indicates potential disruptions to photosynthesis, hindering plant growth and viability. Addressing leaf curling in its early stages can prevent deterioration and promote healthier plant development. To identify the contributing factors, it’s essential to assess various aspects of plant care. Let’s explore the key factors that may lead to cannabis leaves curling and strategies to address them effectively for optimal plant health and growth.
Also Read: Why My Cannabis Seedlings Are Growing Slowly?
Why are my Cannabis Leaves Curling upwards?
Upward leaf curls, known as canoeing or tacoing, occur when leaves point towards the light, resembling a taco or canoe shape. Environmental factors such as high temperatures, nutrient deficiencies, and improper watering can contribute to cannabis leaves curling. Understanding these causes is essential for diagnosing and addressing the issue effectively. To combat leaf curling, it’s crucial to first identify the underlying problem. Let’s delve into the common issues contributing to leaf curling and explore strategies to mitigate them for healthier cannabis plants.
1. Environmental Stresses and Leaf Curling
When you provide the right surroundings cannabis flourishes. Let us check what problem you are facing:
- Temperature Stress
The ideal temperature for cannabis bloom is around 68- 75 F. When this range exceeds, it starts stressing due to moisture loss and cellular damage causing curled leaves. So, to prevent this issue, keep the grow area 70-80 F during the day and 60 F at night.
Install heaters in winter and air coolers or fans in summer according to the season. Additionally, maintain ventilation and adjust the water schedule as per weather conditions.
- Humidity Problems
Humidity plays a significant role in cannabis leaves curling, both high and low humidity cause issues. When the humidity is low, plants lose water quickly via transpiration, and leaves curl inwards to minimize water loss. Cannabis plants are sensitive and more likely to curl leaves when the air is dry. Use a humidifier to raise the humidity level in your grow tent between 40- 60% or group plants together to do the same.
It is less likely that high humidity will cause fungal diseases to affect marijuana, which can result in damaged, discolored, spots, and fuzzy growth. To combat this, use fans and maintain good air circulation. Also, ensure soil is not soggy and reduce watering.
- Light Stress
Anything under or over is bad for your cannabis harvest. The same applies to lights. As cannabis plants are generally grown indoors, light plays a vital role in photosynthesis for energy. Low light levels will not produce chlorophyll, and high light levels will cause yellowing of cannabis leaves and curling.
Excessive light intensity can cause cannabis leaves to curl up at the edges, resembling a taco shape, and this phenomenon is known as “tacoing.” Along with leaf curling, growers may observe stunted growth and leaf bleaching, which can adversely affect plant health and productivity. To mitigate the effects of light stress, it’s essential to maintain an appropriate light cycle during different growth stages. For the vegetative stage, a light cycle of 18 hours on and 6 hours off is recommended, while during the flowering stage, transitioning to a 12-hour light cycle followed by 12 hours of darkness promotes optimal flowering and bud development.
Similarly, if you see cannabis leaves curling inwards in a claw shape, your plant is trying to absorb more light. Increase the light intensity or keep it close to the light. Always use LED or CFL designed especially for growing areas. Use a light meter to schedule lightning.
2. Nutrient Imbalances and Leaf Curling
Nutrient imbalances can lead to various issues in cannabis plants, each nutrient deficiency manifesting in distinct symptoms. Understanding these deficiencies is crucial for effective plant care and maximizing yields. Let’s delve deeper into the specific symptoms associated with common nutrient deficiencies to better address and rectify them for optimal plant health and growth.
- Nitrogen deficiency (N):
As per Wikipedia, Nitrogen, potassium, and magnesium (NPK), an essential macro-nutrients for healthy plant growth plays a vital role in protein synthesis and chlorophyll production. Nitrogen deficiency causes the leaf to curl upwards or downwards, coloration from green to yellow, and stunted growth.
To combat this issue, increase nitrogen intake via nitrogen-rich fertilizers specially formulated for cannabis plants. You can also use organic manure like composted fertilizer or blood meal to ensure soil pH between 6.0 and 7.0. Do not overdo it, as it may lead to nutrient burn.
Related: Nitrogen: The Silent Hero For Healthy Cannabis Plants
- Potassium and Magnesium Deficiency (P, K):
Both Potassium and Magnesium deficiency cause leaf curling. Potassium deficiency causes the cannabis leaf edge to curl downwards or inwards like a claw, with bronzing leading to little growth and weak stems.
Magnesium deficiency leads to upward leaf curling, known as cupping or clawing. Veins start to look yellow mottled pattern. Factors such as low-quality fertilizer or incorrect soil pH raise this problem.
To help, adjust the pH level by sprinkling some Epsom salt for pH balancing. Do not overfeed your plants, and try the soil flush technique.
- Calcium, Sulfur, Iron, Manganese, Copper, Zinc, and Boron Deficiencies:
While Nitrogen, Potassium, and Magnesium are the major nutrients that cause curling in cannabis, deficiencies in micronutrients can also be culprits. Here is a quick view of some micronutrients and how their deficiency affects leaves, along with remedies:
- Calcium (Ca): Deficiency can cause stunted growth, weak stems, and upward curling of leaf tips. Provide cal/mag supplements or use dolomite lime during soil preparation.
- Sulfur (S): Deficiency is rare but can cause stunted growth, pale yellowing, and upward curling of young leaves. Epsom salts (magnesium sulfate) can address both sulfur and magnesium needs.
- Iron (Fe): Deficiency shows as interveinal yellowing (green veins with yellowing between) and stunted growth. Iron chelates are available as supplements, but addressing pH issues is crucial for iron uptake.
- Manganese (Mn): Deficiency causes uneven yellowing on young leaves with brown spots. Use manganese chelates as supplements, but be mindful that manganese toxicity can occur.
- Copper (Cu): Deficiency is uncommon but can cause wilting, stunted growth, and downward curling of leaf tips. Use copper sulfate supplements sparingly, as excess copper is harmful.
- Zinc (Zn): Deficiency is rare but can cause stunted growth, leaves bronzing, and upward curling. Use zinc chelates, but be cautious.
- Boron (B): Deficiency can cause stunted growth, thickened and brittle leaves, and downward curling. Boron supplements are available.
3. Pests – Viruses and Leaf Curling
Aphids, thrips, and spider mites are the most common pests causing leaf curling in your cannabis garden. Also, diseases like cucumber mosaic virus CMV and Hop Latent Virus (EMDV) cause molting and distorted leaves.
For this, use neem oil spray, insecticidal soaps, or predators. Monitor plants regularly and maintain proper hygiene in the grow area.
Related: Identifying and Treating Common Cannabis Pests and Diseases
4. Improper Watering and Cannabis Leaves Curling
When it’s about watering cannabis plants, you have to be extra careful. If you are doing it wrong, the plant will signal you by curling the leaf. There are two reasons behind it:
- Under-watering
When cannabis plants do not get enough water, they stress and curl leaf tips inwards or downwards dry or brittle leaves to reduce water loss. If you suspect this, water your plants until it drains from drainage holes. Allow the soil to dry a bit before watering again.
- Over-watering:
It’s surprising, but over-watering also causes leaf curl. A plant receiving too much water deprives the roots of oxygen, resulting in drooping, yellowing, wilting, and less growth. The soil also releases a foul odor due to root rot.
To combat this, cease watering and allow the soil to dry fully. Ensure sufficient drainage and use a well-aerating pot mix. If the root rot is severe, remove the plant and repot it in fresh soil.
Genetic and Cannabis Leaf Curling
Some cannabis strains are naturally more prone to curling leaves than others. It can be due to inherent traits in the plant’s genetic makeup. For example, Sativa-dominant strains with thinner leaves might be more susceptible to curling under specific environmental conditions than Indica-dominant strains with thicker leaves.
Also, the physical structure of the leaves may influence their tendency to curl. Strains with thinner, more delicate leaves might curl more readily than strains with broader, sturdier leaves in response to stress factors.
So, ensure ideal temperature, humidity, watering, and nutrients to minimize curling, even in genetically prone strains, and consider strains known for resilience and less prone to curling in future growth.
Why are My Leaf Tips Curling Down?
Downwards curled leaves signal several problems like root damage, incorrect humidity, or temperature. Here is how to know:
1. Improper Humidity
Low humidity leads to cannabis plants losing water more rapidly through transpiration. To compensate, the leaves curl downwards, reducing their surface area and minimizing water loss. It is a common cause of downward curling leading to dry, crispy, and slow growth.
2. Improper Temperature
When the temperature gets too hot, plants lose moisture with downward curling to conserve water. It might infest bleached or scorched leaves.
3. Root Damage
Overwatering, underwatering, pests or disease infestation prevents plant water supply leading to downward curling. It causes leaves to turn yellow and show pest attack.
4. Wind Burn
The leaves of cannabis are sensitive to wind and excessive air movement causes a condition called wind burn. The plant does this to reduce the surface area exposed to the wind, minimizing the damaging effects of wind shear friction and excessive transpiration.
Minimize airflow outdoors by sheltering plants and indoors by adjusting fan position. Provide extra support to the stem and maintain humidity levels.
Also Refer to: What Cannabis Seeds Look Like?
Diagnosing Cannabis Leaves Curling
Curling leaves in cannabis can be frustrating, but the good news is you can identify the cause and take corrective action. Here’s how:
Observation is Key: Pay close attention to the curling pattern. Is it curling upwards, downwards, inwards, or outwards? Look for discoloration alongside curling: yellowing, bronzing, or spotting.
Observe how the curling progresses. Does it affect new or old growth first? Are there other signs of stress, like stunted growth or wilting? It will help you to know what is your cannabis plant telling you.
Tools for Diagnosis
- Soil Testing: A soil test can reveal nutrient deficiencies or imbalances that might be causing the curling.
- pH Meter: Maintaining proper soil pH ( 6.0-7.0 for cannabis) is crucial for nutrient uptake. A pH meter helps ensure the correct range.
- Magnifying Glass: A magnifying glass can help you inspect the leaves for signs of pests or diseases causing the curling.
Diagnostic Techniques
Use online resources or books with pictures of cannabis leaf problems to compare symptoms and identify potential causes. Trust your observations and eliminate possibilities. For example, if the temperature and humidity seem optimal, those factors are less likely to be the culprit.
FAQS-
1. Do curled cannabis leaves go back to normal?
Cannabis leaves going back to normal depends on the severity and cause of the curl. In some cases, leaves might recover with early detection. For severe damage or genetic predisposition, curling might be permanent. New growth happens once the plant recovers.
2. How to fix the leaf curling up?
To fix cannabis curling up, first diagnose the issue. Upward curl often indicates nutrient deficiencies, light stress, heat stress, pests, etc., and take the necessary steps.
3. How to fix the leaf curling down?
To fix the downward curl, look for symptoms of under-watering, over-watering, cold stress, or nutrient deficiencies, and then take preventive measures.
4. What are the common signs of leaf curling?
Common signs of leaf curling are upward or downward curl, Inward or outward curling, Discoloration (yellowing, browning), Stunted growth, and Wilting.
5. How to prevent marijuana leaf curls?
To prevent marijuana leaf curls, always maintain proper temperature, humidity, and light and use a well-draining mix and balanced nutrients. Water according to plant needs, avoid overwatering, monitor for pests and diseases, and practice sanitation. The least is to choose resilient strains and reduce stress factors.
6. Is leaf curling a serious issue?
Leaf curl itself might not be fatal, but it indicates an underlying problem. If left unaddressed, it can hinder growth, reduce yields, and make plants more susceptible to other issues.
Conclusion
Keep an eye on your cannabis plants; they will alert you to any problems. Vigilance is the power of treating and recognizing the underlying cause of a plant’s problem, whether it’s temperature, watering, or anything else, and then, with appropriate information, supporting your plants is the only method to cure plant health and growth.
Most importantly, always use high-quality cannabis seeds from reputable suppliers, since you get what you sow!
