Lighting, whether it’s LED, HPS, CMH, fluorescent or the sun, remains one of the most debated topics when discussing cannabis cultivation. Whether it’s the confusing acronyms, the skeptical claims or simply the pace at which lighting systems are advancing, there’s one thing we can all agree on: Lighting has fundamental importance to a successful harvest. Here, Fluence Bioengineering Director of Marketing Travis Williams explains the science behind lighting, the technology behind LEDs and why knowing a few basic terms will go a long way toward cultivation (and operational) success.

Light is electromagnetic radiation—everything from gamma rays to radio waves—but typically when we speak of light, we’re referring to the visual portion of the spectrum between 400 nanometers (nm) and 700 nm. This band of the electromagnetic spectrum also coincides with the type of light plants use for energy to drive photosynthesis and other biochemical reactions. In a nutshell, light is the force behind plant growth and a key variable driving plant development.

In short, because it’s an extremely new topic and an extremely new technology. It wasn’t that long ago every crop on Earth was grown under the sun. There was nothing to debate, nothing to decide nor research. It simply was what it was. Now, with LEDs, we have the technology to fine-tune lighting to the micromole, nanometer and genotype to optimize crop yield and quality. The debate is derived from the exploration—some think they have it figured out, but the truth is, we’re all experimenting.

That it’s a debate between technologies (i.e., HPS or LED). The truth is, it’s a debate between how efficiently a lighting system can deliver the optimal photosynthetic photon flux density (PPFD) and spectrum in a form factor that is optimized for its environment. Growers should look beyond the underlying technology and instead focus on key metrics such as average PPFD across the canopy, spectrum, efficacy and how efficiently the size and durability of the system fits into their facility to maximize yield per square foot.

Chlorophyll is the pigment primarily responsible for absorbing light to provide energy for photosynthesis. Its absorption peaks at 450 nm and 660 nm, which visually corresponds with blue and red light. And when we mix the two, we see purple. The thought was plants only need red and blue light for photosynthesis; however, recent research has revealed countless other pigments also responsible for photosynthesis as well as development impacting cannabinoid and terpene profiles in cannabis. Given these new insights, more growers are realizing the benefits of a broad light spectrum.

I always advise growers to learn the fundamentals of photobiology. Once a grower understands the associated terms and how plants use light, he or she is empowered to look beyond the marketing and evaluate lighting systems (and lighting companies) based on science, not hype.

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