cannabis light burn
Growing Tips

What You Should Know About the Cannabis: Light Burn and Light Stress


Indoor growers need to be careful while using high-intensity growing lights. Too much light stress can lead to permanent damage to your plants.

The problem is that plants can hold on to a specific amount of light. After that, the leaves will begin to lose their greenish side (turning yellow).

As mentioned earlier, this problem usually occurs in indoor gardening, where plants absorb artificial light to thrive. If you take preventative measures, you can secure the plant's health or life.

In this article, we’ll further explain cannabis light burn at different stages of cannabis growth. Believe us; this post is worth reading for your plant’s sake.

What is the Light Burn and Light Stress of Cannabis?

Whether artificial light or sunlight, lighting has been the most significant factor in your plant's health. It doesn’t matter if you are growing cannabis or not; plants need light to process photosynthesis.

In the indoor growing environment, artificial or growing lights are the only source for plants to absorb carbon dioxide CO2 and water. The only and most common problem that every indoor grower may face is light burn and light stress of cannabis. However, you can outrun this problem by taking precautions and knowing the causes of cannabis light burn.

cannabis light burn

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Solving the light burn issue will not only ensure the safety of plants but also helps you to regain the high potency bubs. So how would you know if your plants are going through a light burn or light stress? The only way to save plants is to understand what is causing your plant to burn; it could be the light burn or nutrient deficiency.

The only symptom of light burn or light stress is turning green leaves into yellow from the top. It only happens to those leaves that are under the grow lights. On the other hand, nutrient deficiency follows many symptoms such as yellow leaves, yellow or brown edges, holes in leaves, purple or red tone of leaves, and yellow lining of leaves veins.

Why Cannabis Experience Light Burn and Light Stress?

Cannabis light burn is often called light bleaching because it shows the same signs you get after bleaching (white/brownish color.) Nowadays, it’s more common in indoor cultivators as many are switching to high-intensity growing lights, resulting in light burn and light stress.

 light stress cannabis

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To avoid light burn, use LED grow light for low intensity. LED grow lights emit less heat as compared to fluorescent or HID bulbs. But that doesn’t mean you should also put them too close to the plants. Always use optimal distance while placing LED grow lights above your cannabis plants.

The light burn leaves influence chlorophyll. As a result, it stops the process of photosynthesis, which turns the green leaves into yellow. The symptoms of light stress and light burn can vary during different stages of cannabis growth.

Let’s have a closer look at the symptom of mild burns and mild stress at different phases of cannabis growth:

Seedling Stage

Apart from other growth stages, the seedling stage is the most delicate phase of your plant’s life as it decides the future of your cannabis plant. At this stage of the cannabis growth cycle, the plant is more hazardous to light burn and light stress.

The very first leaf coming out from the seed is also capable of absorbing light and transforming it into food. The first leaf that emerges from soil or seed is also known as dicotyledons.

At this point, your plants are too sensitive to light. If it’s too far, the emerging plant will grow fragile and drops over since its truck/stem can’t handle its size. The LED grow light shouldn’t be too adjacent to the plant as it can cause light burn to seedlings. The light should be optimal where the seedlings get considerable heat.

If you aren’t sure or experienced enough to use grow lights, you can pass the seedling stage in little sunlight on your porch. Remember, seedlings don’t require intensive lights.

Vegetative Stage

The vegetative phase is next after the seedling stage, where little fan leaves and leaflets turn into big, mature leaves. All the pressure to grow faster and healthier is put on stems and leaves at this stage.

All of the focus of the entire plant is to grow bigger and thicker. Unlike the seedling stage, the risk of cannabis light burn is off the chart in the vegetative stage. But that doesn’t mean the plant won’t get any light stress or light burn. Though they perform well in intense light, they need protection from high-intensity light.

The cannabis vegetative stage is about maturing and getting stronger as the day passes. The photosynthesis process becomes more active in the vegetative phase, giving plants more growth. It requires more light and heat to increase the process of photosynthesis. You can now put LED grow lights closer to the plant’s canopy.

While increasing light intensity, you must be more active and regularly monitor your plants' progress. If the leaves start to turn yellow or there are any bleaching signs, place the grow light a bit further back, so the plant doesn't get the light burn or light stress.

Flowering Stage

Flowering is the last and most crucial stage of cannabis growth. All of the hard work you’ve done depends on this stage. If this fail, your whole cultivation is nothing, just a waste. Because harvest takes place in this stage.

Here’s the exciting part, the flowering stage requires less light and heat than the vegetative stage. The color of cola buds will determine whether it’s ready to harvest or not. If somehow, the flowering stage gets cannabis light stress, the color of the buds turns white, and the potency will be gently removed from the buds. All of your efforts to harvest a beautiful crop will go in vain.

Cannabis light burn led

That’s why it’s essential to put the lights away at some distance so the excessive heat of grow lights cannot be able to reach the flower buds.

How to Solve Light Burn and Light Stress of Cannabis?

Once a famous Dutch philosopher said, “Prevention is better than cure.” Your first priority must be the prevention of cannabis light burn before it causes harm to your cultivation. Because once anything gets infected, it won’t bring the original one back. That’s why you should take preventive measures to control the temperature throughout the growing stages.

Cannabis light burn led

Keep in check the following measure to stay away from the cannabis light burn leaves situation:

  • As you know, light stress cannabis is caused by excessive growing light towards plants. To check the intensity of LED lights, place your hand under the light just above the canopy to see if it’s causing any discomfort or irritating your skin. If you find it too hot, your plant is also receiving that heat from lights that aren’t good for it. In this scenario, the grow lights should be pushed back further so your plants get the optimal amount of heat.
  • If you’ve changed the growing area or some plants, give them the same amount of light as in the previous one. Otherwise, they will start showing the side effects of light-stress cannabis.
  • Grow lights play an essential role in indoor gardening. If you are using fluorescent or HID bulbs, make sure to keep a close eye on the temperature of your growing area because these bulbs emit a lot of heat. If you are too concerned with the lights, always go with the LED grow lights. LED grow lights will minimize the chance of getting your plants’ light burned and light stress.
  • Always use the LUX or PAR meter to determine the intensity of heat your plants are getting from lights. When your plants are in the vegetative stage, the most favorable level of lux is anything between 30,000 to 70,000 lux/m2. And when the plant is in the flowering stage, it should be around 50,000 to 90,000 lux/m2. On the other hand, the recommended PAR levels the favorable growth is 200 to 400 PPFD for seedling, 400 to 600 PPFD for vegetative, and 600 to 900 PPFD for the flowering phase.
  • Lastly, if growing in a congested area, consider the slow-stress training at the beginning to prevent the light burn or light stress from your indoor growing.

There’s no repairing of burnt leaves unless you prevent them from happening. Cannabis light burn is not a virus or mold-like disease. It’s entirely in your hands to prevent it from happening. All you have to do is install LED grow lights for your setup and watch out for any rising or descending temperature. Indoor gardening is only experience growers, not for beginners. If you don’t know about indoor gardening, make sure to do some research before starting.