1. Chasing Canopy
A very common LED mistake we see too often happens as a result of growers purchasing underpowered LED lighting. There are only so many ways to increase light intensity: increasing power, redirecting light, or shortening the distance between light and canopy. In order to increase intensity beyond what their light is capable of, growers will opt for the third method, decreasing the distance between light and plant. While it works to increase light intensity, it’s a costly maneuver for commercial outfits that may operate hundreds or even thousands of grow lights. The lights will continuously need to be readjusted to compensate for the growth of the plant because even LED’s relatively low temperatures are enough to stress out a plant if it’s too close, especially if that light is being run at full power. We call this tactic of constantly raising and lowering your lights “chasing canopy,” because that’s all you’re ever doing.
Purchasing a high-intensity LED light is a perfect fix to chasing canopy. You can hang the light at a fixed height and increase or decrease light levels as the plant grows. Premium high-intensity LED models will also go the extra mile by incorporating polycarbonate lensing to direct light downward, cutting down on the amount of light wasted out the sides. Alternatively, low-intensity LED grow lights make an excellent supplemental light, and due to their lower heat, can be utilized vertically by the pragmatic grower.
2. Using an Incorrect Spectrum
All grow lights want to emulate the sun as close as they can because all plants evolved to grow in sunlight. As the seasons change, the natural lighting outdoors changes slightly based on the angle that the sunlight hits the earth. LEDs with full-spectrum capabilities mimic this with an ability to adjust the ratio of colors being emitted from the light in order to produce photomorphogenic responses in the plants. Through the manipulation of the full spectrum of light, you can signal plants to grow taller, shorter, heartier, to flower sooner or later, or to maintain its current size.
High-end LED fixtures like the Fohse A3i give users the ability to change spectrums that simulate seasons like spring, summer, and autumn. The Spring Spectrum mimics the natural light levels of the season by supplying the plants with a higher concentration of blue light, and a smaller amount of red and far-red light. This triggers a photomorphogenic response within the plant, encouraging it to vegetate and grow.
After the first 2-3 weeks in flower, switching to the Summer Spectrum provides a higher concentration of intensity of red spectrum light, which can signal the plants to stretch. This can be beneficial to cultivators trying to get their plants to new heights, but if the technique is applied too heavy-handedly, it could result in weak, skinny plants.
An inexperienced grower might just turn the light on Summer spectrum, thinking it will give their new plants exactly what they need, but instead, be bombarding them with more light than they know what to do with. This can stress and damage the plant, causing wilting and pigment loss in the leaves. This is why it’s important to learn the nuances between spectral settings, when to implement them, and their relationship to overall light intensity.
3. Running the Light at Full Power
New LED users may be so excited about the efficiency of their new purchase that they want to run it on full power as soon as possible. On a smaller light, this may not be an issue, but with a powerhouse like the Fohse A3i, most professional growers don’t even use its full power.
While cannabis is a light-hungry crop, supplying more light can have adverse effects if the plant isn’t in the right stage of development, and/or if the resources aren’t there to allocate all that photon energy to lead to an increased rate of photosynthesis and photorespiration. Increasing photosynthesis causes the plant to work faster and harder, consuming more resources, which means more water, more nutrients for the soil, and higher concentrations of CO2 in the air. If those resources aren’t there, or if the plant doesn’t have enough biomass (and chloroplasts by proxy), all that extra light energy can negatively affect your crop.
One benefit of a powerful light is that you can run it lower than its max output, around where smaller lights would cap. This allows the light to run more efficiently than a light working at full power. LED grow lights operate least efficiently at full power, and exhaust their lifespans more swiftly. Similar to a car being pushed to its top speed, running a light at full power will exhaust its lifespan quicker than one kept lower than its max.
4. Keeping the Room Too Cool
Cannabis performs photosynthesis at optimal efficiency within a specific temperature range, a goldilocks zone from 25º-27ºC (77º-80ºF) . At higher temperatures, if CO2 is increased, the Goldilocks zone can extend to around 85-88º and force the plant to photosynthesize at alarming speeds, packing on bulk as it absorbs nutrients from the soil. This requires the plant to consume a lot of water, and if the room is being dried out by intense heat, that means constantly introducing more water into the grow environment. This happens a lot in HID grow rooms. A large portion of HID lighting’s output is infrared heat, which raises the temperature on the surface of anything its light touches. From canopy to soil to the floor of the room itself, if it’s under HID lighting, its being bombarded with radiation, heating to an uncomfortable temp. Because of infrared radiation, in HID grow rooms, Leaf surface temperature is often 10º-20º hotter than the ambient air temperature. HID owners must keep their air conditioning on at around 65º-70ºF. Since hot air rises, the introduction of this cool current creates hot and cold zones throughout the canopy that stress the plants.
LED grow lights tend to produce far less radiant heat than traditional HID lighting and no infrared heat. So, while HID grow rooms have to turn their air conditioning up high to keep their plants from overheating, LED rooms do not have to compensate in a similar manner. New users may not be familiar with this, and keep their rooms cool as they would normally with an HID room, effectively knocking their crop out of the goldilocks zone, and hurting their yield. Experienced LED users will actually operate their AC units less, and allow the ambient temperature in the room to grow to about 82-85º, which provides a steady, even temperature throughout the canopy.
Discover the technology behind Fohse’s thermal management system:
5. Allowing Too Much Humidity
Higher ambient air temperatures allow the air to hold more water, which is why muggy environments often feel “heavy” with humidity. That’s because, technically speaking, the air is heavier! It is holding a larger amount of water vapor and therefore exerting more pressure on the environment. An LED room run at 82-83º will need a higher humidity than an HID room run in the 70s in order for it to maintain an adequate Vapor Pressure Deficit. That shouldn’t be a problem as the increase in light levels that LED delivers can help plants transpire at faster rates, drawing moisture from the rootzone and expelling it into the air. One of the most noticeable changes a cultivator will notice in an LED environment is that their dehumidification systems will be working more. This is due to the greater volume of moisture being held in the warmer room, as well as the increased rate of transpiration from more productive crops.
Sometimes, HID lights can create negative feedback loops due to the abundance of heat put off by the fixtures. The excessive heat creates the need for more cooling, which in turn cools and dries the air too quickly, removing the humidity. The dryness in the air draws more water from not only the plants, but directly from the soil as well. So, while HID rooms typically need a humidifier, LED rooms, with their higher ambient temperatures, may require a dehumidifier.
6. Over Watering
Because of the increase in humidity in an LED grow room, the root zones of plants grown under LEDs retain moisture better than those in an HID grow room. New LED users may miss this and over water their plants. This can lead to mold, mildew, root rot, and maybe even harmful bugs and bacteria if not immediately dealt with. New LED users should be wary of overwatering, and take note of how the new conditions brought about by LED affect the plant at the root and leaf zones. Light is one of nine parameters that must be tweaked and altered in order for a plant to grow optimally. But when light is altered, it changes the quality, affecting every other parameter of the plants’ environment, from the top of the canopy to the bottom of the root zone. All parameters must be re-evaluated, which may seem taxing at first, but the result will be a grow room that operates like a well oiled machine, producing unbelievable yields with diverse cannabinoid and terpene profiles.
If you have questions about LEDs visit fohse.com, and speak to the pros. Fohse clients enjoy a growing rolodex of helpful cultivators all maximizing their yields through high intensity LEDs. Join the future, today.
