Home » Dealing with Light Burn and Light Bleaching in Cannabis Plants: Causes, Prevention, and Treatment

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Dealing with Light Burn and Light Bleaching in Cannabis Plants: Causes, Prevention, and Treatment

18.04.2023 0

The art of growing cannabis is a complex and rewarding endeavor that requires attention to detail at every stage of the plant’s life cycle. One of the pivotal factors affecting explosive growth and healthy foliage is light. While exposure to ample light is critical, it can also lead to severe damage in the form of light burn and light bleaching. These issues can leave growers perplexed, with their greenery suddenly turning yellow or crispy. Fortunately, there are ways to prevent and treat these problems, ensuring the optimal growth and health of your plants. In this article, we will delve into the causes, prevention, and treatment of light burn and light bleaching in cannabis plants, and help you master the art of light management.

The Importance of Light in Cannabis Growth

Light is one of the crucial factors that greatly affect the growth and development of cannabis plants. Without it, cannabis plants will not be able to perform photosynthesis, which is the process that enables them to produce energy and create their own food. However, while light is essential, it can also cause harm to the plants if not managed properly. The presence of light burn and light bleaching, in particular, can significantly damage the crops, resulting in stunted growth and reduced yields. In this section, we will delve deeper into the significance of light in cannabis growth and explore the causes and prevention of light burn and light bleaching. To avoid making common mistakes, such as improper lighting setup in grow rooms, read our helpful guide on common mistakes in lighting setup for grow rooms.

What is Light Burn in Cannabis Plants?

Light burn refers to a condition where the cannabis plant is damaged due to excessive heat and light exposure. This phenomenon primarily affects the topmost part of the plant, where the leaves receive the most amount of light.

When the leaves get too much light or heat, they start to discolor and dry out. The affected leaves first appear as small yellow spots or patches, but as the damage progresses, the entire leaf can turn yellow, brown, or even black. Eventually, the leaf dies and falls off.

The table below summarizes the signs and symptoms of light burn in cannabis plants:

It’s important to address light burn as soon as it’s observed as it can severely impact plant health and yield. To do this effectively, it’s essential to understand the causes of light burn and how to prevent and treat it.

What is Light Bleaching in Cannabis Plants?

Light bleaching is a phenomenon that can occur in cannabis plants when they are exposed to extremely high levels of light intensity. This causes the leaves of the plant to lose their green pigmentation and turn white or yellow. Light bleaching can occur due to a number of reasons, some of which are listed in the table below.

It is important to note that light bleaching can severely damage the plant and affect its growth and yield. It is essential for growers to take preventive measures to avoid light bleaching in their cannabis plants. If the plant is already showing signs of light bleaching, timely treatment should be given to prevent further damage.

Causes of Light Burn and Light Bleaching in Cannabis Plants

As a cannabis grower, it is crucial to understand the causes of light burn and light bleaching in your plants. These issues can significantly impact the quality and yield of your crop, and identifying the root cause is vital to preventing and treating them. Excessive heat from grow lights, overexposure to light, improper distance from light source, and genetics are some of the primary factors that can contribute to light burn and light bleaching in cannabis plants. By gaining an understanding of these causes, growers can take proactive measures to ensure the health and vitality of their plants.

Excessive Heat from Grow Lights

One common cause of light burn and light bleaching in cannabis plants is excessive heat from grow lights. When grow lights produce too much heat, it can cause the plant’s leaves to become yellow and crispy, ultimately resulting in the plant’s death.

There are several factors that contribute to excessive heat from grow lights, such as:

To prevent excessive heat from grow lights and mitigate the risk of light burn and light bleaching, it’s important to choose the right grow lights, adjust the distance between the lights and the plants, and provide proper air circulation and ventilation within the grow area. It’s also important to monitor the temperature within the grow area regularly to ensure that it remains within a safe range.

Overexposure to Light

Overexposure to light can also lead to light burn and light bleaching in cannabis plants. Too much light can essentially “fry” the leaves and other parts of the plant, causing damage and reducing its overall health and yield.

The following table outlines the potential effects of overexposure to light:

While cannabis plants require a certain amount of light to grow and thrive, it is important to provide the right balance and avoid overexposure. This can be achieved through proper distance from the light source, as well as choosing appropriate types of grow lights and using reflective equipment to distribute light evenly. If overexposure has already occurred, trimming affected leaves and branches, reducing light intensity and duration, and providing nutrient-rich water and soil can help to treat and prevent further damage.

Improper Distance from Light Source

One of the main causes of light burn and light bleaching in cannabis plants is having an improper distance from the light source. This is why it is important to know the recommended distance to make sure that your plants are not getting too much light.

If you place your plants too close to the light source, they will receive too much light, which can cause bleaching or burning on the leaves. On the other hand, if you place your plants too far away from the light source, they may not receive enough light, which can result in poor growth and yield.

To avoid this issue, it’s important to follow the recommended distance guidelines provided by the manufacturer of your grow light. Use a measuring device to make sure that the distance is accurate.

In general, high-intensity lights should be placed further away from the plants, while lower-intensity lights can be placed closer. An example of the recommended distance would be to have your high-intensity lights between 18-24 inches (45-60 cm) away from the plant canopy, while low-intensity lights can be placed between 12-18 inches (30-45 cm) away.

Remember that the distance between the light source and your plants should be adjusted based on the growth stage of your plants. Seedlings, for example, need less intense light and should be placed further away, while mature plants require more intense light and can be placed closer.

Making sure that your plants have the proper distance from the light source takes a bit of trial and error, but it is essential for the healthy growth of your cannabis plants.

Genetics

Genetics play a crucial role in determining a plant’s susceptibility to light burn and bleaching. Some strains are more tolerant of intense light than others and are less likely to experience damage.

Factors to Consider
When choosing genetics for your cannabis grow, there are several factors to consider to reduce the risk of light damage. Look for strains known for their tolerance to high light levels, which are often characterized by their thick leaves and strong stems.

Avoiding Strains with Light-colored Leaves
Strains with light-colored leaves, which typically indicate a lower concentration of chlorophyll, may be more susceptible to light damage. Instead, look for strains with darker leaves, as they often contain more chlorophyll and have a higher tolerance to intense light.

Get to Know Your Strains
It’s important to research and understand the specific strain’s optimal growing conditions, as well as its potential pitfalls. Some strains perform better in areas with high light levels and may require extra light, whereas others may not require as much and may even suffer if exposed to too much light.

Working with Your Genetics
If you’ve identified your strain as being more susceptible to light damage, you may need to take extra precautions by providing extra shade and reducing light levels. Conversely, if you’re working with a strain known for its high tolerance to light, you may be able to provide it with a more intense light source without concern for damage.

Understanding your strain’s genetics and its response to light is crucial to managing light burn and bleaching in cannabis plants. Take the time to research and select the best genetics for your specific grow, and work with them to create the ideal growing environment.

Prevention of Light Burn and Light Bleaching in Cannabis Plants

As a cannabis grower, prevention is key to ensuring healthy and high-yielding plants. Light burn and light bleaching are common issues that can cause irreversible damage to your valuable crop. To prevent these problems, it’s important to take steps to ensure that your plants are getting the right amount and type of light. Here are some prevention strategies you can implement to keep your cannabis plants healthy and thriving.

Choose the Right Type of Grow Light

To prevent light burn and light bleaching in cannabis plants, choosing the right grow light is crucial. There are several types of grow lights available on the market, but not all of them are suitable for cannabis cultivation. Here are some factors to consider when selecting the most appropriate grow light for your cannabis plants:

• Light Spectrum: Choose a grow light that emits light in the spectrum range of 400-700 nm, commonly known as the photosynthetically active radiation (PAR) spectrum. Cannabis plants require this spectrum for photosynthesis and optimal growth.
• Light Intensity: The intensity of your grow light should be appropriate for the size of your grow space and the growth stage of your plants. Seedlings and clones require less intense light, while mature plants require higher light intensity for optimal growth and flowering.
• Light Duration: Cannabis plants require a specific light cycle to flower and produce buds. During the vegetative stage, plants need 18-24 hours of light per day, while during the flowering stage, they require 12 hours of light and 12 hours of darkness. Choose a grow light that allows you to adjust the light duration accordingly.
• Type of Light: There are different types of grow lights available, such as high-intensity discharge (HID) lights, light-emitting diodes (LEDs), and fluorescent lights. HID lights emit a lot of heat and require proper ventilation, while LEDs are more energy-efficient and emit less heat, but can be more expensive. Fluorescent lights are the least intense but also the most affordable option, making them ideal for small grow spaces or beginners.
• Brand and Quality: It is important to choose a reputable brand and high-quality grow light to ensure its performance and longevity. Cheaper, lower quality lights may not produce the necessary spectrum or intensity, and may also pose a fire hazard.

By considering these factors and choosing the right type of grow light, you can prevent light burn and light bleaching in your cannabis plants, and ensure healthy growth and optimal yields.

Adjust the Distance Between Light and Plants

As mentioned earlier, one of the causes of light burn and light bleaching in cannabis plants is improper distance from the light source. It is crucial to adjust the distance between the grow lights and plants to prevent this issue.

Here are some steps you can take to properly adjust the distance between the light and plants:

• Read the manufacturer’s instructions. Different types of grow lights have different recommended distances from the plants. Always refer to the instructions that come with your grow light to determine the optimal height.
• Start with a greater distance. If you are unsure of the exact distance, begin with the light further away from the plants than you think is necessary. You can always gradually lower it as needed.
• Observe the plants. Pay close attention to the plants’ leaves during the first few days under the grow lights. If they start to curl, change color or appear burnt, it is a sign that the light is too close, and you should increase the distance.
• Check the heat. Place your hand at the same level as the top of the plants to feel the heat. If it feels too hot for your hand, it is likely too hot for the plants. In that case, you should raise the light further away.
• Adjust as needed during growth. As the plants grow, so should the light. Adjust the height according to the manufacturer’s instructions and your observations.

By properly adjusting the distance between the light and plants, you can avoid light burn and light bleaching in your cannabis plants, leading to healthier and more productive growth.

Use Reflective Equipment to Distribute Light Evenly

To prevent light burn and light bleaching in cannabis plants, it is important to use reflective equipment to distribute light evenly. Here are some tips on how to do this effectively:

• Choose reflective surfaces: Opt for surfaces that reflect a high percentage of light such as Mylar, white paint, or reflective materials specifically made for indoor gardening. This will allow the plants to receive light from different angles, minimizing the chances of hot spots.
• Position the reflective surfaces: Place reflective surfaces below and to the sides of the plants. This will bounce light back up and around the plants, ensuring that they receive light from all angles without any direct exposure.
• Use reflective walls: If possible, paint the walls of your grow room with a high-quality white paint to reflect as much light as possible. You can also add reflective material to walls, but make sure it is sealed tightly and free from any wrinkles or folds that could create hot spots.
• Consider a light mover: If you have a large grow room or multiple grow lights, a light mover can distribute light evenly over a large area. This device moves the grow light back and forth, covering more space and reducing the risk of hot spots.

By using reflective equipment, you can ensure that your cannabis plants receive light evenly, which will not only prevent light burn and light bleaching but also promote healthy plant growth.

Provide Sufficient Darkness for Recovery

In order for cannabis plants to recover from light burn and light bleaching, it is crucial to provide sufficient darkness for them to rest and rejuvenate. This is because plants use darkness as a crucial part of their metabolic process, allowing them to synthesize energy and nutrients through photosynthesis during the day and break them down at night.

During the recovery process, plants need more darkness than usual. It is recommended to switch to a 12-hour light schedule during this time, giving the plants 12 hours of darkness and 12 hours of light. This balance will allow the plants to recover while still receiving the necessary light for growth.

It’s important to note that during this period, the plants should not be exposed to any additional light sources, including ambient light from nearby rooms or streetlights. Light leaks can disrupt the plants’ circadian rhythm and cause additional stress, hindering their recovery.

Additionally, it’s important to maintain a consistent light schedule throughout the recovery period to prevent further stress. Creating a schedule and sticking to it can help the plants acclimate and recover more quickly.

By providing sufficient darkness during the recovery period, cannabis plants can bounce back from light burn and light bleaching, continuing their growth and development with renewed vigor.

Genetic Selection

One of the most effective ways to prevent light burn and light bleaching in cannabis plants is through genetic selection. This involves choosing strains that are naturally resistant to excessive light, heat, and environmental stressors.

By selecting strains that are adapted to your growing environment, you can avoid many of the problems associated with light burn and light bleaching. Some strains are naturally more resilient than others, and can tolerate higher levels of light without suffering damage.

When choosing your strains, consider their natural genetics and their growth patterns. Look for strains that are known for their hardiness, resilience, and adaptability, as these traits are often associated with plants that are less susceptible to light burn and bleaching.

Another factor to consider is the age of your plants. Younger plants are generally more susceptible to damage from excessive light than mature plants, so you may want to choose strains that are well-suited to your growing environment in order to avoid problems down the road.

To help you choose the right strains for your needs, here is a table outlining some of the most popular strains for indoor cannabis cultivation and their preferred growing conditions:

By selecting the right strains for your growing environment, you can reduce the risk of light burn and light bleaching in your cannabis plants, and enjoy a healthier, more productive harvest.

Treatment of Light Burn and Light Bleaching in Cannabis Plants

Now that we understand the causes and prevention of Light Burn and Light Bleaching in Cannabis Plants, let’s focus on the treatment of these issues. Dealing with light stress in plants can be stressful and worrisome for growers, but it’s important to act quickly and effectively to save your crop. In this section, we’ll discuss the steps you can take to help rejuvenate your cannabis plants from light burn and bleaching. It’s crucial to keep in mind that prevention is always the best approach, but if the damage has already occurred, don’t despair, there are still ways to help your plants recover. So, let’s explore the different treatment options available to ensure your cannabis plants thrive.

Trimming Affected Leaves and Branches

When dealing with light burn and light bleaching in cannabis plants, it may be necessary to trim affected leaves and branches in order to promote healthy growth. This is especially true for leaves and branches that have turned yellow or brown as a result of the damage. Trimming can be a helpful practice because it prevents the plant from expending resources on damaged tissue, which can ultimately lead to stunted growth or even death.

However, it is important to note that over-trimming can also be harmful to the plant. Only trim damaged or dead leaves and branches to avoid harming the plant. When trimming, it is best to use a clean, sharp pair of scissors or pruning shears to minimize damage to healthy tissue.

In addition to trimming, it is also important to treat the affected areas with a high-quality plant healing solution to promote quick recovery. This will help the plant to repair any damage that has already been done and prevent further damage in the future.

Trimming affected leaves and branches can be an effective way to promote healthy growth in light-burned and light-bleached cannabis plants. Just be sure to do it carefully, only remove damaged or dead tissue, and follow up with proper treatment to prevent further damage.

Move Plants Further from Light Source

One of the most effective ways to deal with light burn and light bleaching in cannabis plants is to move them further away from the light source. This approach can help reduce the amount of light that reaches the plant and prevent further damage.

To move your plants away from the light source, follow these steps:

• Start by turning off the grow lights and giving the plants some time to cool down.
• Carefully lift and move the plants to a new location that’s further from the light source. Be sure to avoid damaging the roots or any other part of the plant.
• Monitor the plants closely for a few days after moving them to ensure they’re growing as expected and not suffering from any additional stress.

It’s important to note that moving your plants too far from the light source could have negative effects on their growth and development, so be sure to find a good balance between distance and light intensity. Additionally, make sure you’re following the other preventive and treatment measures to ensure your plants continue to grow healthy and strong.

Reduce Light Intensity and Duration

One of the most effective ways to treat light burn and light bleaching in cannabis plants is to reduce light intensity and duration. This can be done in the following ways:

It is important to note that reducing light intensity and duration should be done gradually to avoid shocking the plants. Additionally, it is important to monitor the plants closely during this process to ensure that they are responding positively to the changes. If done correctly, reducing light intensity and duration can be an effective way to treat light burn and light bleaching in cannabis plants.

Provide Nutrient-Rich Water and Soil

When a cannabis plant experiences light burn or light bleaching, it can suffer from nutrient deficiencies. Providing nutrient-rich water and soil can help the plant recover and even prevent further damage. Here are some tips for providing nutrient-rich water and soil:

• Choose quality soil: Cannabis plants thrive in well-draining soil that is rich in nutrients. Choose soil that contains organic matter and minerals.
• Use nutrient-rich water: Cannabis plants require specific nutrients to grow and flourish. Use water that has been pH-balanced and treated with nutrients such as nitrogen, phosphorus, and potassium.
• Consider supplements: In addition to nutrient-rich soil and water, consider using supplements such as compost tea or liquid fertilizer to provide an extra boost of nutrients to your cannabis plant.
• Watch for signs of nutrient deficiencies: Even with nutrient-rich soil and water, cannabis plants can still suffer from deficiencies. Keep an eye out for yellowing leaves or stunted growth, which can be signs of nutrient deficiencies. Adjust your soil and water accordingly.
• Don’t overfeed: While it is important to provide nutrients to your cannabis plant, be careful not to overfeed. Overfeeding can lead to nutrient burn, which can cause even more damage to your plant.

By providing your cannabis plant with nutrient-rich soil and water, you can help it recover from light burn or light bleaching and ensure that it continues to grow strong and healthy.

Use Shade Cloths to Filter Light

One effective solution for preventing light burn and light bleaching in cannabis plants is using shade cloths to filter or reduce the amount of light the plants receive. Shade cloths are typically made of polypropylene or polyester material and are designed to provide different levels of shade. Typically, they come in percentages ranging from 10 to 90. Here are some benefits of using shade cloths to filter light:

• Regulate Temperature: When using a shade cloth, it can help regulate the temperature by reducing the intensity of the light, which can reduce the amount of heat being released by the grow lights. This could help keep the temperature at an optimal level for plant growth.
• Reduce UV radiation: Shade cloths can also reduce the amount of ultraviolet (UV) radiation that cannabis plants receive, which can be harmful to the plants. UV radiation can cause discoloration or bleaching of the leaves.
• Customizable shade levels: Shade cloths come in various percentages, ranging from 10 to 90, which means growers can customize the amount of shade they provide to their plants based on their specific needs. For example, if a grower feels their plants are receiving too much light, they could use a 50% shade cloth to provide the desired amount of shade.
• Budget-friendly: Shade cloths are quite affordable and can provide an effective solution for preventing light burn and light bleaching. They can also be reused for multiple growing seasons.

When using shade cloths, it is important to make sure they are secured properly to prevent them from falling onto the plants. Additionally, the shade cloths may need to be adjusted as the plants grow to ensure they are receiving the proper amount of light. Using shade cloths is an easy and effective solution to help mitigate the risk of light burn and light bleaching in cannabis plants.

Conclusion

In conclusion, dealing with light burn and light bleaching in cannabis plants can be a challenging task, but it is essential for ensuring the health and productivity of your plants. The importance of light in cannabis growth cannot be overstated, but it can also be the source of problems if not managed properly.

By understanding the causes and prevention methods of light burn and light bleaching, you can develop effective strategies for keeping your plants safe and healthy. Choosing the right type of grow light, adjusting the distance between light and plants, using reflective equipment, providing sufficient darkness, and selecting appropriate genetics are all essential prevention measures that can help you avoid these problems.

If light burn or light bleaching does occur, there are several effective treatment options that can help your plants recover. Trimming affected leaves and branches, moving plants further from the light source, reducing light intensity and duration, providing nutrient-rich water and soil, and using shade cloths to filter light are all effective methods for treating these issues.

In the end, the key to dealing with light burn and light bleaching is to remain vigilant and proactive. By monitoring your plants regularly and taking corrective action as soon as you notice any symptoms, you can prevent these problems from becoming more severe and damaging your plants irreversibly. By following the guidelines outlined in this article, you can ensure that your cannabis plants receive the optimal amount of light they need to thrive and reach their full potential.

Frequently Asked Questions

What are the signs of light burn in cannabis plants?

The signs of light burn in cannabis plants include dry and brittle leaves, yellowing or bleaching of leaves, and an overall burnt appearance of the plant.

Can light burn affect the potency of cannabis plants?

Yes, light burn can affect the potency of cannabis plants by weakening the flavor, aroma, and THC content of the buds. It can also reduce the amount and quality of resin production.

How can overexposure to light cause light bleaching in cannabis plants?

Overexposure to light can cause light bleaching in cannabis plants by damaging the chlorophyll in the plant cells, which reduces the plant’s ability to absorb light and produce energy through photosynthesis. This leads to the bleaching of leaves and a weakened growth rate.

What grow light is suitable for preventing light burn and light bleaching in cannabis plants?

LED grow lights are suitable for preventing light burn and light bleaching in cannabis plants because they produce less heat and their light spectrum is closer to natural sunlight.

What is the ideal distance between grow lights and cannabis plants?

The ideal distance between grow lights and cannabis plants should be between 12-18 inches, depending on the grow light’s intensity and the plant’s stage of growth.

How can reflective equipment help distribute light evenly to cannabis plants?

Reflective equipment such as Mylar sheets or reflective grow tents can help distribute light evenly to cannabis plants by reflecting light back onto the plants and reducing hotspots.

What is the best way to provide sufficient darkness for cannabis plant recovery?

The best way to provide sufficient darkness for cannabis plant recovery is by giving plants a full 12 hours of uninterrupted darkness every 24 hours. This helps the plant rest and recover from any stress caused by light burn or bleaching.

Can genetic selection prevent light burn and light bleaching in cannabis plants?

Genetic selection can help prevent light burn and light bleaching in cannabis plants by choosing strains that are more tolerant to intense light and heat. However, proper growing practices are still necessary to prevent any negative effects.

What nutrients are essential for cannabis plants recovering from light burn or light bleaching?

Cannabis plants recovering from light burn or light bleaching need nutrients such as nitrogen, phosphorus, and potassium, as well as micronutrients like magnesium and calcium. These help promote healthy growth and repair damaged tissues.

How can a shade cloth help filter light and prevent light burn in cannabis plants?

A shade cloth can help filter light and prevent light burn in cannabis plants by reducing the intensity of the light that reaches the plants. It can also distribute light more evenly and reduce hotspots caused by direct exposure to light.

References

• Cannabis Light Burn & Light Bleaching Symptoms & …
• Cannabis cultivation – Wikipedia