How to

22 March 2021

How to Grow Cannabis Using LED Lights

Up until a few years ago, Metal Halide (MH) and High-Pressure Sodium (HPS) lighting reigned as the industry standard for growing cannabis. Long ago, marijuana growers discovered the dual lighting systems covered the necessary light requirements for optimal cannabis plant growth.

MH bulbs emitting cool blue wavelengths provide an ideal lighting source for vegetative stage growth. However, they lack the necessary output from the red spectrum required for prime flower development. To remedy this predicament, growers switch to HPS bulbs when flipping the light schedule. These bright, high-intense bulbs cover the yellow, orange, and red wavelengths required to produce bodacious buds.

Several years back, LED grow lights manufacturers introduced a one-stop-shop for cannabis growers. Instead of switching from MH to HPS when flipping into the flowering stage, LED’s offer full-spectrum light for all phases of cannabis plant growth.

While early designers experienced some growing pains, modern LED manufactures are redefining systems to enhance plant growth development. Studying the intricate role of light’s contribution to marijuana plant growth, lighting designers have learned how to harness light control.

As LED lighting technology continues to unfold, exciting discoveries and designs are advancing cannabis cultivation. Read on to learn more about how to grow cannabis using LED lights.

The Science Behind Light Control

Light is an essential component in cannabis plant development. Shining down from above, the plant absorbs light energy and converts it into chemical energy through photosynthesis. Plants use the energy from light’s electromagnetic radiation at specific wavelengths most suitable for their development.

While plants absorb energy from wavelengths between 400 to 700nm for photosynthesis, different waves are necessary for specific functions. For instance, photosynthesis’s sweet spots for taking in enough light energy fall into two areas. Cool blue light wavelengths between 430 – 450nm drive vegetative growth, while longer red waves between 640 – 680nm encourage flowering plants.

The design of full-spectrum LED lights captures all of these essential wavelengths in a single fixture. By utilizing unique structuring, different light-emitting diodes can be strategically placed within a unit to encourage photosynthesis throughout the cannabis plant’s growth development. More interesting, the ratios between blue to red wavelength diodes within a fixture also promote plant growth.
LED Lighting Options for Cannabis Plants

Standard LED Panels

Some of the first LED lighting components introduced to the cannabis industry were panels composed of many small to medium diodes with compact lamps. These traditional fixtures showcased a combination of both blue and red spectrum wavelengths. While it took a few years of fine-tuning, these designs offer a mix of the wavelength spectrum, customized to a marijuana grower’s needs.

Chips On Board (COG)

This relatively new technology places an LED chip into contact with a substrate to produce LED ranges. COBs have a high lumen density, blasting the cannabis plant with bright white light. These powerful systems allow deep light penetration throughout the canopy as they mimic the sun’s rays. COB LEDs use a single circuit design, allowing for multiple diodes on a chip.

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Spread Style LED Light Variations

Quantum Boards

This popular LED set-up uses low wattage diodes spread throughout a flat board. Arranged in parallel rows, powered by a continuous current driver, these efficient LED configurations provide good light spread due to their intense white light. Most reputable quantum boards come equipped with passive cooling features, allowing plants closer contact to the light source without the worry of light burn.

Spider-Style LEDs

These aptly named fixtures resemble the eight-legged insect by the shape of the design. With the main body running down the middle, extending arms reach out to illuminate a wide light distribution. Similar to the quantum board designs, spider-style LED lighting spreads light equally throughout the canopy with fully equipped diodes delivering an abundance of bright light.

How to Choose the Best LED Lighting for Cannabis Cultivation

As you can see, there are plenty of options available for LED lighting configurations, but knowing which style is the best for a marijuana grow room requires a bit more science.

Measuring the output of a particular LED fixture is one way of determining its efficiency.

Photosynthetically active radiation (PAR) is the range of the light spectrum used by plants to synthesize light rays. While PAR reveals the number of photons emitted within the parameters, it does not divulge how much light is absorbed by the plant.

Photosynthetic Photon Flux Density (PPFD), on the other hand, reveals how much PAR per second reaches the plant. PPFD readings show different light intensity depending on the location from where the plant is measured. While lighting manufacturers generally provide PPFD measurements on product labels, typically, their calculations only reveal the middle area of the canopy, forgoing statistics on outer growth readings.

When looking at options for LED light fixtures, apply due diligence in research as many manufactures only divulge certain aspects of their products. Cheaply made LED lighting components, often from overseas, may look like a great bargain but are typically composed of lesser quality components. High-quality LED manufacturers may charge more for their units, but the cost-savings will save marijuana cultivators in the long run.

Cannabis growing under coloured LED lights

Advantages of Growing Cannabis Plants Under LEDs

Higher Return On Investment (ROI)

While LED lighting components usually carry a hefty price tag, looking at the overall ROI might sway a cannabis grower to fork out the extra initial cost. A closer look at the money spent on dual light systems using MH and HPS lighting options, not to mention the labour involved in changing the light ballasts and reflectors during the flip is worth analyzing. Initial costs of LED lighting aren’t cheap, but the result leads to a higher ROI.

The efficiency of LED lighting is a game-changer in cannabis cultivation. Compared to the energy costs of MH and HPS bulbs, LEDs are energy efficient as they use less electricity, saving growers from outlandish utility bills. Additionally, the durable fixtures have much longer lifespans when compared to other high-intensity discharge (HID) lights, reducing costs on replacement equipment.

LEDs require less energy for output, resulting in much cooler environments. Traditional lighting methods, especially HPS lights, emit tremendous heat requiring cooling and ventilation systems within the marijuana grow space. LED lights emit less heat, eliminating costs on these spendy expenditures when designing specific growing room environmental controls.

LEDs can be customized for specific marijuana grow environments. Small and large diode configurations of light spectrums, spread out proportionally over a canopy, encourages plant development through all life stages.  Controlling the amount of light in a grow tent enables marijuana growers to capitalize on maximum yield from their crop.

Use LED Lighting to Benefit Cannabis Plant Growth

Strategic Light Placement for Optimal Growth

Because LEDs emit light at cooler temperatures compared to HID lights, they can be placed closer to the canopy without the worry of light burn on leaf tips. Even with intense light rays blazing down on marijuana plants, LEDs typically will not fry upper leaves, unless of course, the plant becomes so big it grows into the light.

Knowing how far to place a LED lamp above a cannabis plant depends on several factors, but wattage is a good indicator for height variables. In general, the rule of thumb is to place plants 30 – 60cm (12 – 24in) under a 300-watt fixture is typically a beneficial range for plant development. On the other hand, components with higher wattage should be raised to the 70 – 80cm (28 – 31in) mark for optimal plant growth. Always check the lighting manufacturer’s guidelines for proper distance recommendations.

Another consideration determining the distance between LED lights and plant canopy depends on the stage of growth. Pushing photosynthesis in the vegetative state requires abundant light. Placing LED fixtures closer to the plant at this stage promotes the natural process. As the stretch in the pre-flowering phase takes off, though, height adjustments need to be administered to prevent leaf burn and bleaching.

More Light Output, Less Nutrient, and Water Inputs

LED lights maintain cannabis grow room temperatures much lower than traditional HID components. Cooler temps reduce evaporation, meaning moisture is retained longer in the substrate. Watering frequency slows down considerably under LED lighting, especially compared to hot, HPS bulbs.

Less watering, Less Nutrient Dosing

Most nutrient formulas are applied to cannabis plants via root drenching in a soluble solution. As the watering frequency declines due to saturation, adjust nutrient recipes as needed. Cannabis plants still need to be fed their veg and flowering formulas, but alterations to nutrient dosing may need to be applied.

The Strain Sets the Stage

The type of cannabis strain to be grown directly affects LED light requirements. For instance, a tall, sprawling high THC sativa-dominant beauty may need a wide light span to encompass the massive plant. Compared to a small indica variety with a thicker, dense leaf structure, a shorter dynamic configuration may work best.

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Post author
Charle Thibodeau
Charle’ Thibodeau is a freelance writer with almost a decade´s experience, specializing in cannabis content for the past two years. A strong motivation to educate, inform, and promote the culture surrounding this miraculous plant is her earnest mission.
See more from Charle Thibodeau

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