led grow lights flowering cannabis

Providing Insufficient Lighting It is important to consider the scale of your operations. Think about how many plants you’re growing and how many LED lights you’ll need in order to illuminate them properly. You should also be aware of the luminosity of the lights you’re using. For example, a 200W LED light is said to be sufficient for a yield of about 100 grams. Make sure that you have enough lamps but still look for a good balance between providing sufficient lighting and not overdoing it.

Setting the Lamps at an Improper Distance Overheating or insufficient lighting can result from having too many or not enough lights, but it can also result from placing the lights too close or too far from the plants. There is no universal rule for setting the distance but it’s recommended that LEDs are placed 12 to 18 inches away from the plants.

For people who use cannabis derived products on a regular basis, it is very tempting to try growing the plant at home. The benefits are quite obvious: the cost is drastically lower and there aren’t any hassles related to the actual purchase of medical marijuana. Many people all around the world grow cannabis at their homes, be it for recreational or medicinal purposes, and while some of them do quite well and manage to produce a good product, for others it doesn’t work so well – their plants wither quickly or produce insignificant yields.

In this article, we’ll provide you with the 10 most common things you should pay attention to when using LED grow lights so you can grow healthy looking plants and avoid any unnecessary hassle. This information is extremely relevant to beginners.

Overwatering When Switching from HIDs to LEDs Regular HID lights produce a lot of heat and generate lots of infrared light. This dries out the plant and the soil and results in the need to water the plant more often. However, LED lights generate no infrared light and don’t emit nearly as much heat, so there is no need for abundant watering.

Overheating the Plants You will know the plant is taking too much heat if the leaves that are closest to the light start turning brownish. The first signs look like thin outlines on the outside of the leaves, so if you catch this quickly you will have a chance to avoid further damage. If some of the leaves start curling up, it might also be a sign that the plant is too close to the light. Good ventilation usually also helps with this issue.

Grow lights are a great tool for making the growing process more efficient, but they can also be harmful to the plant if not used correctly. Here are 10 things you should avoid doing when using LED and other types of grow lights.

Forgetting to Adjust the Lights Many people forget to adjust the height of the lights as the plants grow bigger and end up with burnt leaves. Another important thing is to occasionally rotate the pots in order to prevent the plants from leaning towards the light too much.

These issues can be related to improper usage of lighting. (The same issues affect other types of plants as well.) Grow lights are a great tool for making the growing process more efficient, but they can also be harmful to the plant if not used correctly.

Using the Wrong Light Schedule You should be careful not to leave the lights on all the time, or worse, the opposite – forget to turn them on. It might sound trivial but it’s quite easy to mess up the light schedule and even a minor change might have a negative impact the plant’s growth. Cannabis needs about 18-24 hours of light during the vegetative stage and 12 hours of light during the flowering stage.

Not Protecting and Maintaining the LED Lights LED grow lights are your friend and an important investment, so you need to take proper care of them. They bring numerous benefits to the growing process and a little maintenance and preparation can save you a lot of trouble. It is recommended that you set up a power stabilizer and connect it to the lights in order to equalize the incoming voltage, thus protecting the chip inside the LEDs.

Using Inferior Products Light is among the most vital factors to consider when growing plants because it triggers the photosynthesis process. If you’re using regular incandescent lights, you’re not very likely to grow strong and healthy plants. Therefore, for best results it is recommended that you use full spectrum LED grow lights. They are specifically designed for the purpose and have the feature to deliver light in the exact spectrum the plant needs.

Source: Maximum Yield, May 31, 2019.

Not Considering the Other Factors LED grow lights are a great aid when growing plants indoors but by themselves they cannot do much. In order to produce big and healthy yields there are a lot of factors that need to be considered – room temperature, airflow circulation, soil, nutrients, plant genetics, and many others things. Don’t just focus on a single part of the growing process. Instead, try to get an overall understanding of the whole chain and how everything is interconnected.

Selecting the Wrong Light Spectrum In order to grow efficiently, plants need different types of light for each growth stage. With full-spectrum LED lights this is easily achievable, but if you select the wrong setting, the plant will not develop well. You should also take into consideration the conditions in the room where you’re doing the growing. For example, plants benefit most from light in the blue spectrum when they’re in the vegetative stage of growth. That means that if you set the light to emit light in the red spectrum, you will only be hindering the plant’s growth.

Grow lights are a vital piece of equipment that every aspiring grower should have. Although they are easy to use and set up, you should pay attention to this list of common mistakes and save yourself from headaches.

As a plant that does not have sufficient lighting in veg will not produce as well in flower. That said, the spectrum with the most blue did produce the flower with the most terpenes and THC.

It was only after companies like P.L. Light and Philips* introduced LED fixtures specifically engineered for truss mounting in a greenhouse, that growers really adopted this technology. These products enabled even the indoor grower to maintain some distance between the LED fixtures and the plant canopy, and resulted in production similar to growing under HPS. (*In the United States, Philips has taken the stance that they will not support sales into the cannabis industry as it is not recognized to be legal by the federal government)

ALWAYS ask for a light plan that shows an average light level in micromoles AND a uniformity average (hopefully above 90% uniformity). Most LEDs are a very directional source of lighting. If a crop is grown under lighting that is not uniform across your canopy but instead has “hot spots” and “dark spots” it will cause you trouble as the hot spots will use more water, evaporate water, absorb nutrients, etc. at a different rate of speed then the dark spots! To truly have an “apples to apples” comparison be sure to compare light plans with the same targeted light level in micromoles and close to the same average uniformity number. If a supplier cannot provide you with these numbers then it may not be someone you should be considering.

Cannabis Research in Canada.

What about growing in a greenhouse? From our graph above showing the spectrum of sunlight compared to that used for photosynthesis is there any benefit for using a light source where you can dial in the spectrum to add more blue? The natural light received by your crop in a greenhouse will cover all of your light spectrum needs. So the big question for greenhouse grows should center more around the ROI comparisons between LED and HPS — not about light spectrum needs. This is not something you will hear from light manufacturers of LED lighting. Your LED-only supplier will have you believe you NEED their spectrum specifically!

To use the PL Light TopLED R/MB as an example: 320W fixture with PPF of 860 μmol is 2.7 μmol/J (860 / 320 = 2.6875) where the 1000W DE HPS has an output of 2100 μmol is 2.1 μmol/J (2100 / 1000 = 2.1). This is important because I have sat in many presentations, by LED manufacturers, who show how quickly they can hit a good ROI with their LED and use 1.85 μmol/j as their HPS comparison. They’re not lying about this but they are using the old single-ended screw in 1000w HPS lamp in the comparison. These lamps have an output of 1850 μmols at 1000w. But, it is an old technology only in use by small hobby grows these days. I have seen manufacturers use as low as 1.7 μmol/J for HPS which would be the equivalent to the end of life of the old HPS technology.

In countries like Canada, where the federal government has legalized recreational cannabis, there is the ability to do more research. The University of Guelph is one organization that is leading the way in this research. As he states in this article from HortiDaily — Michael Dixon, Director of Environmental Control Research at Guelph says: “We have found that the optimal LED spectral recipe changes with every strain of cannabis.” This is a very important statement for growers to consider! Will you be growing just one strain in your grow the entire time? If not, what spectrum do you choose? Yet if the added blue light in flower only increases your THC levels by 4% is there a justifiable ROI in the cost of the added light spectrum?? If so, can you do that by just adding a few MH lamps? Or does the ROI make sense to go all LED? (1000w DE MH lamps are now available with the PL Light NXT 1000w DE fixtures).

Do this math with your LEDs as well. The PL Light TopLED is 320 watts so the BTUs will be 1092 BTUs. While that looks like a big savings it will take at least two times the amount of our LEDs to get to the same light level as a 1000w HPS. On the other side of this argument is that the LED fixtures do not provide the radiant heat as HPS and your crop roots will perform better with warmth. It is proven that there is a direct correlation between heat and crop production. Plants grow slower, producing less fruit the colder they are. In northern climates many growers rely on the heat from HPS to warm their crops.

Most of these “new to horticulture” LED manufacturers are making claims that you should be using a full spectrum LED in flower to truly maximize plant terpenes and THC levels. But is this really true? See the graph below comparing what parts of the light spectrum is used for photosynthesis compared to the full spectrum light from the sun.

“What lighting source should I use for my licensed cannabis grow?”; “I am comparing LED to HPS for my cannabis operation. Which source do you recommend?” These are questions people ask me almost on a daily basis. We have covered this question in past posts on our blog, like this one by our very own head of marketing: LEDs vs Traditional Lighting but most cannabis growers know that this crop is different than most and many growers have experimented with lighting technologies on a small scale to find they can sometimes increase terpenes and THC levels just by changing their light sources. To begin, let’s unpack the information that exists on this complex topic.

Canopy Penetration.

Disclaimer Nothing in PL Light Systems including, but not limited to, written, visual, or editorial content, or external links on the website and digital journal, shall in any way be considered as promoting any illegal or illicit activities within your jurisdiction.

This is a big consideration to consider when comparing these technologies. There is no easy math to calculate an ROI for this but when comparing light plans from one source of light to another be sure to take into consideration the distance of the light source from the canopy.

There is a lot of information out there on the internet from various growers and lighting suppliers. You can find a contradiction to almost every point you find! Most growers agree that for young plants through the veg stage of growth you will want to have a light source with a good amount of blue light or even white (full spectrum) lighting. The main reason for this is to reduce internode stretching to produce a stockier, healthier plant.

With LEDs most will use μmol/J (“Micromoles per joule” with joule being a measurement of watts). This is easy math you can do yourself.

Light Planning.

When comparing both technologies, always compare light levels of the entire grow and not just fixture to fixture. I cannot stress enough that there is no such thing as a 1-for-1 replacement of HPS by LED! That simply does not exist in the marketplace. Yes, there are LED fixtures that exist when measured directly beneath the fixture. The output looks equal to or even greater than an HPS. But, when you move the PAR sensor any direction from centered beneath the LED the light level decreases much more under the LED than any HPS fixture!

The bottom line that I can share with you, from my perspective where I get visibility to lots of opinions on the topic, see lots of sales and growth cycles, talk to lots of growers, is this: We are still in the investigative and development stage with LED technology in this sector.

After veg and moving to flower, most growers also agree that switching to a light source with more of the red spectrum is better for flowering. The old standard has been to use either CMH or fluorescents in veg and switch to HPS into flower. This is the tried and true lighting recipe for indoor cannabis growers. By far the majority of cannabis produced in North America today is grown in this way. With the onslaught of LED lighting manufacturers jumping into this new “green rush” of opportunities we are seeing this standard lighting recipe being challenged more and more.

There is a big misconception in the industry stemming from the LED suppliers that the ability to have your LED lights so much closer to your crop will help increase production lower into the crop. This could not be further from the truth! When your light source is closer to the top of the canopy than the shadows created from the top layer of leaves are much bigger than if the light was further away. (Use a flashlight and make a shadow on a wall with your hand. Watch how the shadow grows as you get the light closer to your hand). Also, light penetration into the crop comes from the crossover between fixtures.

Another area you should always do your own math on is the BTU calculation for your grow room. Yes, LEDs produce less heat than HPS and this can be the deciding factor. As the cost to cool your grow room can be one of your highest production costs. Your AC load is based on the amount of BTUs produced from your fixtures. This is simple math as 1 watt equals 3.412 BTUs. No matter what 1000w HPS fixture you use the BTUs from that fixture will be 3412!

How Far to Keep from Plants : 12-18″ away from tops of plants.

Many smaller LEDs are spread out over a large area. Examples of this style include Quantum Boards, Rack and “Spider style” LED grow lights.

Do Your Research!

Average Yields: 5.5-8+ ounces – keep in mind that the strain (genetics) and any plant training you do makes a huge difference in your final yields. Some growers are getting even better yields with this light, it seems to be performing very well in tests.

How Far to Keep from Plants : 32″ is the recommended starting distance from the plants.

Which LED grow light brands can be trusted?

Actual Power Consumption: 270W at full power, and can be dimmed down to 90W for younger plants.

Now that you have a basic understanding of the different types of LEDs, lets talk about using them for growing cannabis.

LED grow lights are a great choice for growers who are dealing with hot HPS lights and want to change to something that’s going to run cooler. Although LED grow lights do produce heat, the smaller models might not bring up the temperature of your grow space.

LEDs vs MH/HPS.

In our growing forum, many members have experimented with different grow lights for growing cannabis. Over the last few months, it has become apparent that one of the most popular brands for LED grow lights is an emerging company known as “ViparSpectra.”

When it comes to growing cannabis, LED models with 3W chipsets (each individual bulb is 3W) seem to get some of the best yields/watt of all LED models without a lot of worry about light-burning your plants.

While Kind LEDs offer several additional models of LED grow lights, because of the price tag on these lamps I’m only listing the ones I’ve seen used by actual cannabis growers, though I’m sure the other ones are likely just as good. That being said, the following models have been proven to work really well for growing cannabis!

Although this is just one example, this is pretty typical of LED grow lights in that they tend to bring out colors. This Eldorado plant was bloomed under two light sources, an HPS on one side and an LED on the other. Nothing scientific, no partitions, so there was light overlap. At harvest the color difference was surprising (see below) and after curing 2 select pieces from each side of the plant, the aromas are slightly different as well.

Breakdown of Different Advanced Platinum LED Models:

Introduction: Are LEDs a Good Choice for Growing Cannabis?

Actual Power Consumption: 184W in veg, 368W in flowering (this model has a separate vegetative and flowering mode)

Actual Power Consumption: 328W.

If you’re most concerned with improving your yields/watt, skip the LEDs and get an HPS grow light for your flowering stage. Although LEDs are catching up and there are some really great LEDs out there that get comparable results, HPS still tends to give you bigger yields when it comes to how much electricity is being used.

Our plants growing under two Electric Sky 300 LED grow lights.

How Far to Keep from Plants: The manufacturers of this Kind LED grow light recommend that the lamp be kept at least 36″ from the tops of your plants for the best results. This model is very, very powerful and keeping it too close will give your plants light burn!

The final yield depends a lot on strain and grow skill, as well as the quality of the lamp itself, but that’s a good rule of thumb for most models. For example, a 200W LED (200W true power draw, not an “equivalent” wattage) would yield about 100-200 grams on average, or 3.5 to 7 ounces .

Kind LED Grow Lights.

How Far to Keep from Plants: The manufacturers of this Kind LED grow light recommend that the lamp be kept at least 36″ from the tops of your plants for the best results. This model is very, very powerful and keeping it too close will give your plants light burn!

Grow Space: 2.5×2.5’ coverage at 36” (suitable for vegetative stage) and 2×2’ coverage at 28” (suitable for flowering stage)

LED grow lights come with built-in cooling systems and heat sinks which vent air up and away from plants. This can make it so that you can hang the LED grow light in your tent and not necessarily need an exhaust system to control the temperature.

Yields! With a quality LED grow light and an average-to-good grow, you can expect yields of about 0.5 to 1g/watt .

Here is a breakdown of their different models. This list doesn’t include all their models, just the ones that seem to be performing the best. We omitted a few that just don’t seem as good as the others for some reason (as one example, the pro version of the 1200W seems to be getting some bad reviews based on its light footprint, despite the fact that all the other models in the series perform very well).

Average Yields: 8-16+ ounces – keep in mind that the strain (genetics) and any plant training you do will make a huge difference in your final yields. This LED model has performed better than most others I’ve tried so far.

Average Yields: 4.5-6+ ounces – keep in mind that the strain (genetics) and any plant training you do makes a huge difference in your final yields.