Prevention is far better than cure, they say. Thus, you must try to prevent light burn rather than trying to cure it. First off, light burn depends on the type of light you’re using. For instance, a CFL hung even 10 inches away from the plant will not damage the plant. The same applies to fluorescent or T5 lights because they aren’t that powerful and don’t emit a lot of heat. However, HID and LED lights positioned even 10 inches away from the plants can kill them.
But, light burn can happen indoors. The leaves and even the buds begin to look white or burnt when the lights are hung too close to the plants. The heat is so high that the plants cannot tolerate it. White buds look amazing when you look at them, but it’s a sign that the buds are damaged.
Similarly, cannabis plants use light as food, but if you install too many lights and hang them too close to the plants, you’re asking for trouble. If you notice your plants struggling, keep reading to figure out how to prevent and treat cannabis light burn.
Leaves turning brown and crisp is an indication of light burn too. It’s a combination of heat and too much light that fries the leaves and render them useless to the plant.
ight burn is nothing but light bleaching. You’ll notice that the leaves too close to the light turn white or look bleached. Plants growing outside cannot suffer from light burn because the sun is too far away from the earth to burn the plants. Cannabis has evolved for centuries and has adjusted to the sunlight enough to not get burnt.
Yellow leaves can also indicate light burn at times. But, do not get confused between nitrogen deficiency and light burn because they look the same. With nitrogen deficiency, though, yellowing of the leaves start from the bottom and move towards the top. Also, the leaves are limp and fall off from the plant without any effort. On the other hand, if they are suffering from light burn, the leaves feel crispy and are harder to pluck from the plant.
Since the light is too close to the buds, the resin along with the cannabinoids are destroyed. You probably already know that heat kills plants, and buds are no exception. In fact, not only will the buds be useless for both medicinal and recreation users, but the taste goes for a toss too. And the fragrance deteriorates as well.
What is a light burn?
How to prevent light burn?
Light burn or light bleaching is a serious problem if you’ve got a got a room full of cannabis plants. Light serves as food for the plants, but it can als
When we set up grow lights, we position our lights several inches or even farther away from the top our plants, depending on the type of grow light, because we don’t want our plants to get too much heat. But is that the only reason why? If we could reduce the heat in the area, couldn’t we give our plants more light by moving the grow lights even closer? If more light equates to more bud, I could be harvesting more using the same amount of electricity…right?
A plant being grown outdoors in a location with relatively low levels of sunlight could get as low as 32,000 lux (lux is a measurement of light) on a bright sunny day in direct sunlight. Light levels can fall down to 10,000 lux (or even less) on an overcast day. On the flip side, a desert in the height of summer can see light levels as high as 100,000 lux on a sunny day. Cannabis can usually survive at either end of these ranges as long as the temperature, soil, etc. are acceptable.
Return of the Lux Meter
So now that you know about light levels, you have a few tools to help make sure you’re avoiding light problems. The hand test is a good start, the manufacturer’s specs are great for LED grow lights, and a lux meter is great for everything else.
When we measured the amount of light the plants were getting with a lux meter, we got readings between 105,000 and 110,000 lux! This means that these cannabis plants were getting more light than they would on a sunny desert day, but with temperatures in the 70s. We thought this would make the plant grow even faster and better than in the wild. However, even with the heat controlled, not only did we not get faster growth or bigger yields (the opposite actually), problems showed up…
So as plants are using more light, they take in more nutrients than they otherwise would, which can lead to a buildup of nutrients in the plant, causing…
Tip Burn, Nutrient Deficiencies & Dying Leaves
The leaves below show different stages of a mix of what appears to be nutrient deficiencies from an “over-lighted” plant. Changing the nutrients won’t help in this case, but if you fix the conditions by moving the light further away, these symptoms will stop spreading to new leaves. Unfortunately the damage done to the current leaves is permanent.
Each model of LED is different, and needs to be kept different distances from your plants. Unfortunately there’s no “standard” yet for LED grow lights since they use various ways to focus light downward, and these have a huge effect on how much light is experienced by the plant.
Is it possible to give your plants too much light even when the heat is under control? I did some testing and the results are here…