Understanding under-canopy lighting

In commercial cannabis cultivation, growers are tasked with figuring out how to dial in their processes to ensure maximum yields and quality with every harvest. As proponents of data-driven cultivation, we’re all about harnessing the power of science to achieve cultivation goals – and one of the hottest topics in cultivation is under-canopy lighting.

In this post, we explore the growing adoption of under-canopy lights, the science behind them, and what kind of results growers are seeing from them.

The science behind under-canopy lights

Photosynthesis drives biomass production in plants. This process is usually catalyzed by light from the sun, but in indoor and greenhouse environments with supplemental lighting, it’s up to humans to create the conditions that support this natural function.

As lighting has evolved, technologies like HIDs and high-pressure sodium lamps have endured for decades as the standard in greenhouse and indoor cultivation. This paved the way for white LEDs to corner the market as cost-effective lighting solutions, but this made it significantly more difficult for growers to manipulate light in ways that affect plant growth.

The evolution of under-canopy lighting

One of the most significant benefits of outdoor cultivation is that plants have access to the full lighting spectrum of the sun. The sun’s movement across the sky allows photons to reach leaf surfaces from a variety of angles throughout the day, allowing them to interact with chlorophyll electrons and initiate photosynthesis.

In controlled environments, where everything from the number of lights to the amount of electricity used to plant spacing can cause variances in how far light can penetrate the canopy, cultivators may rely upon defoliation and other canopy management techniques to facilitate light distribution.

Under-canopy lighting, which involves adding supplemental lighting to the lower regions of the plant, has emerged in recent years as a viable way to promote growth in areas of the canopy that overhead lights can’t reach.

While the cost-effectiveness of LEDs makes them the go-to solution for lighting beneath the canopy, under-canopy lighting is not simply a matter of turning an LED light fixture upside down and dropping it to the bottom of a bench. Years of grow room R&D have made it clear that everything from the shape of the LED bars and the type of diodes used to the need for easy maintenance and proper heat diffusion make it necessary for these light fixtures to be specially designed for this purpose – and manufacturers are answering the call.

Making under-canopy lighting part of a holistic approach

In an industry that relies upon yield and quality benchmarks as measures for success, operating in balance is crucial for growers. Much like irrigation control and crop steering, under-canopy lighting is ultimately most effective when used as part of a holistic approach to cultivation. Growers who work to ensure plant density, feeding, and irrigation are ideal to begin with are more likely to experience success with under-canopy lighting than those who have to troubleshoot one issue after another.

Applying a holistic approach also means growers must consider the impact that adding extra light and heat beneath the canopy will have on their crops. For example, supplementing with under-canopy lights results in a more even VPD spanning the top, middle, and bottom of the plant, which could change the way the plant metabolizes – and how this expresses itself physically in the plant varies by cultivar.

Growers should also consider the impact that the potential for more yield from each plant might have on production. Defoliation is a prime example of this risk. Growing more biomass toward the bottom of the plant could lead to overcrowding, causing more de-leafing work for the cultivation team and ultimately defeating the purpose.

So for growers who factor in things like cultivar performance and the willingness to reduce plant count and make other accommodations to support the effectiveness of under-canopy, seeing average increases between 25-35% in the first run is not usual.

The exciting potential of under-canopy lighting

For growers who factor in things like cultivar performance and a willingness to reduce plant count – and who make other accommodations to support the effectiveness of under-canopy lighting – seeing average increases between 25 and 35 percent in the first run is not unusual.

So, is under-canopy lighting for you? Consider the following takeaways:

• When full-spectrum sunlight isn’t an option, growers must create optimal lighting conditions to facilitate natural functions like photosynthesis.
• Adding under-canopy lighting – supplemental lighting toward the lower regions of the plant – has emerged as a viable way to promote growth while maintaining quality.
• Growers are more likely to achieve success with under-canopy lighting when adopting it as part of a holistic approach to cultivation.
• While everything from genetics to cultivation practices can influence results, some growers report 25-35% yield increases after implementing under-canopy lighting.

To learn more about under-canopy lighting, check out our interview with FAVEN’s Tim Crowell.

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