The benefits of using supplemental light for the propagation and production of greenhouse ornamental, vegetable, and cannabis crops have been well documented by university researchers and commercial growers. 

Michigan State University horticulture professor Erik Runkle, along with his colleague Roberto Lopez, have done a considerable amount of supplemental light research with a variety of annual bedding plants, including petunia, calibrachoa, and impatiens.

“There is a laundry list of things growers need to look at when considering installing supplemental lighting,” Runkle says. “From a plant perspective, what is the light intensity that should be delivered? What sort of spectrum should be used? Other considerations include the efficacy or energy efficiency of the light fixtures and the cost.”

Runkle says another consideration when choosing LED lights is the people who will be working around the lights.

“Considering the spectrum from the plant’s perspective is important, but sometimes there are also considerations from the human perspective,” Runkle says. “LEDs can emit white light or more of pink or purple light. The purple light can be the most effective from the plant’s perspective, but it can create an unpleasant environment to work in when it is the primary light source. The purple light might be unsettling for people who aren’t used to that light.”

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