Lighting considerations for cannabis grown under glass versus in a more industrial environment are numerous. For starters, free sunlight is fantastic for saving operating capital on energy costs, not to mention the diverse light spectrums received from the sun versus having to replicate those different spectrums with LEDs or multiple High-Pressure Sodium (HPS) lights. Additionally, there are growers who believe natural sunlight provides additional crop protection benefits that artificial, or supplementary lights, simply cannot.
Grower Thought on Lighting
Jake Van Wingerden, a third-generation greenhouse grower situated along Maryland’s Eastern Shore, has been growing medical cannabis in a custom designed, Dutch-style greenhouse under the brand SunMed Growers since receiving a state cultivation license in August of 2017. Today, the operation harvests about 400 plants every week, supplying the state’s processors and dispensaries with about 150 pounds of high-quality (i.e., potency), greenhouse-produced flower and trim (the non-smokable parts of the plant that are often processed into other products like topicals and oils).
“With cannabis, you’re judged on potency and yield; you’re not growing a plant, you’re growing a bud that has a potency associated with it,” Van Wingerden says. “It’s very different from the bedding plant world, which is all about aesthetic appeal. That is not how cannabis is judged.”
When it comes to lighting considerations, Van Wingerden and SunMed have found a direct correlation to the amount of light you give the plants and the yield and potency derived.
“Growing [cannabis] in a greenhouse is great in the summer months, because you get free sunlight every single day, as long as it is sunny,” he says. “In the winter months you don’t have that, and you have to have enough supplemental lighting to compensate, otherwise the crops are not going to be as potent and you’re not going to yield as much.”
SunMed deploys a mix of both LED and HPS lighting in the greenhouse, and Van Wingerden believes the age-old LED vs. HPS debate is more a question of what an individual grower hopes to accomplish via his lighting systems, versus one type being the superior choice.
“LEDs obviously are more expensive fixtures, but at a cheaper operating cost than HPS, which is your tried-and-true standby and fairly inexpensive from a fixture cost standpoint, but also with higher energy costs,” he says.
Bottom line, he says, is dialing in your lighting (and blackout) systems to give the plants their best chance to reach top-end yield and potency potential. In that vein, SunMed leverages Priva greenhouse control systems to automate lighting adjustments throughout the growing process, a system Van Wingerden describes as “the Cadillac of [greenhouse] control systems.”
“The plant wants as much light as possible he says. “If you grow in low light, you’re bound to get low potency and low yields. And if you grow in high light, you’ll get higher potency and higher yields.”
Lighting Manufacturers Weigh In
LumiGrow (Emeryville, CA) is a self-described “smart horticulture lighting company” specializing in LED grow light solutions enabled via cloud-based software. The group has developed smart LEDs for the greenhouse industry for the past 10 years, according to Marketing Director Brandon Newkirk.
Newkirk shares that LumiGrow’s LEDs are labeled “smart” because they integrate with sensors in the greenhouse to allow for instant adjustments based on real-time conditions.
Another strategy that Newkirk is advocating with greenhouse cannabis growers is having them dial in production practices even further by breaking down greenhouses into different management zones that can then be individually managed for a multitude of variables.
“Return on investment is a big talking point right now for a lot of our clients, and it can be measured very accurately for things like yield and quality. Obviously, you need to factor a higher up-front cost with many LEDs, but you also see many growers switching to LEDs now because the payback is so fast. You’re going to pay the same amount one way or another, and our customers would rather own state-of-the-art equipment than tossing money out the window on their utility bills,” Newkirk says.
Meanwhile, Fluence Bioengineering (Austin, TX) says that greenhouse growers producing cannabis need to keep the product’s end use in mind when designing the lighting setups.
“Whether the cannabis will be used for medicinal, recreational, or industrial purposes,” Travis Higginbotham, Global Director of Cultivation Support, says. “Each end user application, especially if the cannabis will be used in its raw form or will be processed to be used in other products, will change the environmental variables you should consider when cultivating cannabis.”
Along those lines, light intensity and Daily Light Integral (DLI) solutions are among two of the more important metrics for growers to keep in mind.
“This means a lack of high intensity lighting during cloudy days or the winter and fall, can negatively impact consistent and predictable plant production,” Higginbotham says. “DLI does not yet have a known independent impact on cannabis, outside of light intensity. However, growers should be highly aware of their facility location and natural light levels during all seasons to maximize their natural light, as well as how to set their supplemental lighting strategy.”
Higginbotham also says that while the moniker “supplemental” may perhaps infer a lesser significance among outsiders, cannabis producers need to be just as vigilant with supplemental lighting and controls in the greenhouse as the primary fixtures.
“These should really be a top consideration to ensure you have the ability to manipulate photoperiods and intensity during all stages of production,” he says. “Growers should also consider the form factor of the (light) fixture for both indoor sole source lighting, as well as for greenhouse supplementation. The form factor, in a greenhouse, should not cause much shading on your crops.”