Light Burn On Weed Plants

By: Maria

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Imagine this: You’ve put in the time, effort, and resources to grow your cannabis plants. You’ve been meticulous about providing the right nutrients, maintaining the ideal temperature, and ensuring optimal humidity levels. But then, you start noticing yellow leaves and bleached buds on your plants. You’re dealing with light burn on weed plants, a common but often overlooked problem in cannabis cultivation.

What is Light Burn on Weed Plants?

Light burn, often mistaken for a nutrient deficiency, is a stress response in cannabis plants exposed to excessive light or heat. Contrary to popular belief, it’s not the light per se that’s the problem, but the imbalance between lighting and other resources that cannabis requires. As light intensity increases, so does the demand for water, carbon dioxide, and nutrients. If these aren’t adjusted accordingly, light stress occurs.

Light burn is more prevalent in indoor cannabis cultivation, where growers must balance variables like the distance of the grow lamp from the canopy and its intensity. Too close, and you’ll encourage light burn. Too far, and your plants will underperform and stretch towards the light source.

Why Cannabis Experience Light Burn?

The primary cause of light burn in cannabis plants is the heat emitted from the light, rather than the photons themselves. Incorrect positioning of your light can literally cook the upper portions of the canopy.

Moreover, the intensity of the light plays a significant role. Cannabis plants can withstand a certain amount of light, but beyond a certain point, they start showing signs of stress on the leaves near the light sources.

Signs of Light Burn on Weed Plants

Identifying light burn on weed plants early is crucial to prevent long-term damage and yield loss. Here are some of the most common signs:

Bleached Buds

One of the most noticeable signs of light burn is the bleaching of the flowers. This phenomenon occurs when flowers are located too close to high-powered lights. You may have seen images online of pure white “albino” cannabis flowers. While they might look interesting, most of the time, they have been rendered useless. The heat degrades cannabinoids present in the resin, causing buds to lose potency. The scent and taste of these buds will also be less than desirable as the terpenes responsible for these traits are highly volatile aromatic hydrocarbons, and excess heat will cause them to degrade.

Yellow Leaves

Yellow leaves are another sign that your plant is being subjected to light burn. However, yellow leaves can also signify nitrogen deficiency. The difference is that yellow leaves caused by this nutritional deficiency start from the bottom of the plant, display significant wilting, and will either fall off or are extremely easy to remove. On the other hand, yellowing caused by light burn will occur at the top of the plant, and these leaves will be much sturdier and harder to remove.

Stunted Growth

Light burn can reduce the rate of growth due to damage inflicted upon the photosynthetic apparatus. Burned leaves begin to lose their water content, shrivel up, and turn yellow. Due to a lack of water, structure, and chlorophyll, affected leaves cannot conduct photosynthesis. During the early stages of development, when plants have few leaves, this can stunt growth and impact plant health further into the growing cycle.

Curling or Clawing Leaves

In some cases, the leaves of a cannabis plant experiencing light burn may start to curl or “claw.” This is often a sign that the plant is trying to protect itself from excessive light and heat. The curling or clawing is a defensive mechanism, with the plant attempting to reduce its exposure to the light source.

Leaf Tip Burn

Another sign of light burn is when the tips of your cannabis plant’s leaves start to turn yellow or brown. This symptom is often mistaken for nutrient burn, but a key difference is that light burn usually affects the upper leaves closest to the light source, while nutrient burn tends to be more uniform across the plant.

Remember, early detection and intervention are crucial when dealing with light burn on weed plants. By keeping a close eye on your plants and adjusting your grow lights as necessary, you can prevent light burn and ensure your plants remain healthy and productive.

How to Solve Light Burn on Weed Plants?

The first step to solving light burn is adjusting the distance between your plants and the lights. This can be done by either moving the plants or the lights, depending on your setup.

If adjusting the light isn’t an option, you can resort to low-stress training (LST) your plants. LST is a technique where you try to keep the plant’s branches all at the same height. As the stem gets taller, it should be bent sideways and kept in that position with an external aid.

Another solution is to decrease the temperature of the room slowly and consistently. Any changes to a plant’s environment need to be done carefully and patiently. It won’t matter how well you water and feed your plants; if you don’t take proper care of the environment, the plant will suffer.

Also, When selecting lights, consider using light-emitting diodes (LEDs) as they emit less heat compared to traditional high-intensity lights, reducing the risk of light burn. Always ensure that the chosen light type and its intensity match the needs of your cannabis plants to prevent overexposure.


Light burn on weed plants is a common issue that can significantly impact your yield if not addressed promptly. By understanding what causes light burn and how to prevent and treat it, you can ensure that your cannabis plants remain healthy and productive. Remember, the key to successful cannabis cultivation is balancing all the variables, including light, nutrients, water, and temperature.

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