burnt cannabis leaves

How To Spot And Treat A Light Burn On Your Cannabis Plants

Although not fixable with a nutrient solution boost, this is a problem that your plant can survive easily. As long as it’s not too late, after this article, you’ll know how to fix it.

This is a problem faced with indoor plants only. If you have an outdoor grow operation and feel your cannabis plants are suffering from light burn, forget it! You’ll probably want to look into other conditions that can show similar symptoms. The sun is too far out to damage your outdoor plants. Cannabis has existed for longer than the human race. It has developed well enough to handle the sun’s heat and light.

Light burn will only happen to an outdoor plant in a specific situation. It might happen if you grew it in the shade and just now transferred it into the light. In cases like this, the plant won’t be used to the heat and light and will eventually die.


• Bleached Buds

One surefire symptom of light burn is 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. This might look like the intentional development of rare genetics, but the fact is, most of the time this is simply bleaching. Luckily, it’s very hard to miss your flowers turning bright white.

Although white buds may look interesting, most of the time they have been rendered useless. The heat degrades cannabinoids present in the resin, which causes buds to lose potency. The scent and taste of these buds will also be less than desirable. The terpenes responsible for these traits are highly volatile aromatic hydrocarbons, and excess heat will also cause them to degrade.

• Yellow Leaves

Yellow leaves are another sign that your plant is being subject 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.


The first thing you should do is move your plants a bit further away from the lights. This can either be done by moving the plants or by moving the lights, if you have the space. Take into consideration the most affected areas of each plant when choosing a new location for them. You can also remove some of your lights. If you have these well organized, it shouldn’t hurt your plants to remove a few bulbs.

If reducing the light or moving the plant isn’t an option, you can always low stress train your plants. This is a technique for obtaining more yields, 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.

Try decreasing the temperature of the room too. Do this very slowly and always keep the temperature consistent. The plant will need time to adjust. Any change you’ll need to make to a plant’s environment or medium needs 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 die.


Growers can also utilise a lux meter to measure how much light different parts of their plants are being exposed to. These devices are used to measure lux, the unit of illuminance, per metre squared. They are handy as they offer readings regarding the intensity of light beaming down on any given area. Lux meters are ideal for hobby and small-scale growers as they are leagues cheaper than other light-measuring devices on the market. Growers can use them to determine if their plants aren’t getting enough light to produce an optimal yield, or if they are getting too much and are at risk of light burn.

A general healthy range for cannabis plants is between 35,000–70,000 lux during the vegetative phase and 55,000–85,000 during the flowering phase. If you notice any of the symptoms above and your lux meter is giving readings above these values, move your light source further away from your plants to reduce the intensity.

This can be a very hard problem to fix if not done in a timely manner. Be sure that you're informed about it if a light burn ever happens to you!

Burns on Cannabis Leaves

  • Escrito por : Ciara
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Burns on cannabis leaves are extremely frequent and they can have many different causes. In this article we’re going to go through some of the most common causes of burns on cannabis leaves. It’s not always due to your lights – plants can have adverse reactions to different climates, nutrients, water or dryness.

One of the most common cases of burns on leaves is due to the height of your lamps; many growers still believe that 60cm is the perfect height for a 600w bulb, and the buds end up dried up while still on the plant. The bulb height should be determined by the temperature at the tip of your plants by using a thermos-hygrometer. When your plants get burned because of the light the most affected zone is clearly the top area of the plant, which goes yellow until it completely dries up.

Another kind of burn that appears on the leaves can be due to unhealthy roots. Roots can become unhealthy for many reasons, such as extreme drought, growing in pots that are too big, watering too much or fertilizing too much. All of these things will cause your plants to start looking ugly and ending up burnt, as the roots will also end up burnt. These kinds of burns show up as small brown freckles on your plants which eventually grow and cover the entire leaf, which ends up falling off.

Many times you’ll need to spray your plants with foliar nutrients or preventive products such as pesticides and fungicides. When spraying, you need to be wary of the light as it can cause burns by magnifying droplets of water. When spraying you need to be sure that in the next couple of hours your plant won’t be receiving excessive light, regardless of whether your growing indoors or out. If you’re growing outdoors you need to spray them either early in the morning if you’re in a cold climate or just before the sun sets if you live somewhere where the temperatures don’t drop too low at night. If you’re growing indoors you’ll need to lift the lights up as much as possible until your plants dry, and if you can’t do that then you’ll need to take them out of the tent or room and spray them, placing them back in once they’ve dried. These burns show up underneath where the droplets of water were, which act like magnifying glasses and intensify the light.

One of the most least-known reasons for burns on cannabis leaves are fans. A direct breeze on your plants constantly can easily cause burns on the leaves, and sometimes it can be mind-boggling trying to figure out why they’re burnt. Even if you have a moving fan, if it’s on too strong and it shakes the plant too much the leaves will dry up faster than they hydrate, so the leaf will end up drying up and falling off. These burns tend to happen on the upper areas of plants where the fan can hit them – the plant closest to the fan is the one that will suffer the most. By lowering the speed on the fan or moving the plants further away from it you should stop the burning. This can be hard inside a small grow tent, where you should youse various fans set at the lowest temperature rather than one strong one.

These are some of the most common reasons for burns on cannabis leaves indoors, which is where it happens the most. It can also happen outdoors if the sun is too strong but it’s not very frequent.

Author: Javier Chinesta
Translation: Ciara Murphy

Burns on cannabis leaves can happen for many different reasons, and this article is here to show you how to identify and treat them.