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 these days 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.

Photosynthesis drives biomass production in plants. Because this process is catalyzed by light, in indoor and greenhouse environments where supplemental lighting stands in for the sun, it’s up to humans to create the conditions that support this natural function. As lighting has evolved, technologies like HIDs and high-pressure sodiums have endured for decades as the standard in greenhouse and indoor cultivations. This paved the way for white LEDs to eventually corner the market as a cost-effective lighting solution, significantly impacting the grower’s ability to modulate light in ways that affect plant growth.

The evolution of under-canopy lighting 

One of the greatest 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 touch leaf surfaces from a variety of angles throughout the day, ultimately leading 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 toward the lower regions of the plant, has emerged in recent years as a viable way to promote growth in areas of the canopy that don’t directly receive light from overhead.

While the cost-effectiveness of LEDs makes them the go-to solution for lighting beneath the canopy, it’s not simply a matter of turning an LED light fixture upside down, dropping it to the bottom of a bench, and calling it a day. Throughout years of grow room R&D, it became 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 so temperatures inside the canopy stay optimal means that these light fixtures must be specially designed for this purpose – and manufacturers are answering the call. 

Does under-canopy lighting work?

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 itself, under-canopy lighting is ultimately most effective when used as part of a holistic approach to cultivation. Growers who put in the time and effort to ensure plant density, feeding, and irrigation are ideal to begin with are more likely to be set up for under-canopy lighting success than those having to troubleshoot one issue after another.

Applying a more holistic approach also means growers must consider the impact that adding extra light and heat beneath the canopy will have on their overall environment and individual plants. 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 it metabolizes – and how this expresses itself physically in the plant varies by cultivar. Another consideration is the impact that the potential for more yield from each plant might have on production. Defoliation is a prime example; growing more biomass toward the bottom of the plant could lead to overcrowding, causing more de-leafing work for the cultivation team – and that ultimately defeats 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.

In Summary:

• 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 25-25% yield increases from under-canopy lighting.

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