How to spot light burn in cannabis plants?

Light burns or bleaching in your Cannabis plants are common problems when using grow lights to cultivate. One of the common symptoms of light burn is bleaching. It happens when the buds or leaves are located too close to high-powered grow lights. Aside from that, another symptom of light burn is when the leaves of your Cannabis plants turn upward and gradually turn yellow. The leaves also lose their luster and become crispy. Though saving them is possible, you have to spot the light burn to administer the possible treatment as soon as possible.

How to spot light burn in cannabis plant?​

What is a Cannabis plant's light burn?

Light burns or light bleaching in your Cannabis are common problems when you use grow lights in cultivating your Cannabis plants. Light is essential since it aids your Cannabis plants in manufacturing their food, energy, and development.

However, when the lighting system is not appropriately regulated, it will cause them stress, resulting in light burns. It happens especially when your Cannabis plants canopies proximity to your grow light is too close.

Instead of appearing the usual green color, the leaves become bleached or even white. Light burn happens mostly to indoor Cannabis plants since they use artificial light source.

In addition to leaves discoloration, too much light can damage your buds, since light and heat both break down cannabinoids and terpenes thus reducing the effects, taste and scent of your buds.

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What causes light burn to your Cannabis plants?

High temperatures can cause light burn, particularly when grow lights are too close to your Cannabis plants. That is why you have to keep a distance between your grow light and Cannabis plants. The best range of temperature is between 64°-77° Fahrenheit (18°-25° Celsius).

Light burn is more likely to occur in grow spaces that have a high temperature and low humidity.

During the vegetative stage, humidity should start at around 70% only. Then, you have to gradually decrease during pre-flowering and half of the flowering stage until 60%. As it reaches the final week of the flowering stage, you have to keep it around 50%.

If you fail to keep the following relative humidity, your Cannabis plants are at risk for heat stress and are more vulnerable to light burn. That is why it is recommended to have a thermohygrometer to measure your growing area’s humidity accurately.

How to identify light burn in your Cannabis plants?

Early-stage symptoms of light burn can sometimes be mistaken for heat stress. The following are the known symptoms of light burn that you have to look for:

  1. The leaves of your Cannabis plants are pointing upwards. It shows up during the initial stage of light burn, especially to the leaves that are very close to your grow light.
  2. As time goes by, the leaves start to turn yellow. Usually, leaves closer or exposed to light tend to become lighter in color than other leaves of your Cannabis plants.
  3. The leaves of your Cannabis plants, especially their tips, will turn yellow. But if you will take a closer look, you will find out the veins remains green.
  4. The leaves of your Cannabis plants start to curl upward to cover themselves. They lose their shine and become brittle. They appear burnt with brown spots.
  5. The buds of your Cannabis plants will start bleaching and will eventually turn bright white. When bleaching of your buds happens, they lose their potency, making them useless.

How to treat light burn in your Cannabis plants?

When you diagnose your Cannabis plants for having light burns, you have to take action immediately to prevent getting to a point of no return. The following things can help you in treating light burn in your Cannabis plants:

  1. Move you lights further up to increase the distance between them and your cannabis plants.
  2. You can also remove some of your lights from your growing space. Removing a few bulbs will not hurt your Cannabis plants if they are suffering from light burn; instead, you can also regulate the lights down if your grow lights have that feature.
  3. You can also low-stress strain your Cannabis plants to treat a light burn. To do this, you keep all the branches of your Cannabis plants be at the same heights. When the stems grow taller, they bend sideways and keep themselves in that position with external support.
  4. Decrease the temperature of your growing space gradually since your Cannabis plants need to adjust. You have to do it carefully and patiently.
  5. Increase the humidity of your grow room if it is too low.

How to prevent light burn in cannabis plants?

Though there are ways to treat light burn in your Cannabis plants, prevention is still better than cure. To prevent further light burn problems, you may do the following to save and keep your plants safe.

  1. Do a basic hand test. Examine if the light is too hot by putting your hand under the light at the canopy level. If you feel like it is causing discomfort to your skin, you have to move the grow lights away from your plants.
  2. Before using a particular grow light, you have to research it. You need to know that different grow lights vary in distance and positioning from your Cannabis plants.
  3. Using LUX or PAR meter will help you determine the amount of light your Cannabis is getting. During the vegetative stage, the lux level must be between 30,000 to 70,000 lux/m2. When your Cannabis plants reach the flowering stage, ensure that the lux level is between 50,000 to 90,000 lux/m2. On the other hand, secure that it is between 200-400 PPFD for seedlings, clones, and mother plants when using the PAR meter. During the vegetative stage, keep it between 400-600 PPFD. 600-900 PPFD is the most ideal when it reaches the flowering stage.
  4. Low-stress training for your Cannabis plants will help you avoid light burn, especially when your growing space is limited. It is a method of bending the stems sideways so that light can penetrate to the canopy of your Cannabis plants. You can reduce the distance between your grow lights and plants by bending them.

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