The experimental set up depicting (A) the inside of one enclosure (i.e., block)encapsulated by panda film, (B) a bench that consisted of three plots, and (C) two trays of cuttings under the white LED treatment (W), centered under the LED fixtures. (Photos courtesy of the author)
Guelph, Ontario Until recently, most clonal cannabis (Cannabis sativa) has been propagated using fluorescent lights. Transitioning to light-emitting diodes (LEDs) may be a viable alternative to fluorescent lighting, enabling cultivators to provide specific spectrum treatments to enhance rooting while also saving energy.
The overall objective of this study was to compare a range of LED spectrum treatments, both fixed and temporally dynamic, with fluorescent lighting for the propagation stage of clonal cannabis. The overall hypothesis is that some LED spectral combinations, either fixed or dynamic, will be superior to fluorescent lighting for producing cannabis transplants. Specific objectives were 1) compare fixed-spectrum distributions that are commonly used in horticultural LEDs (e.g., B mixed with R, phosphor-converted W) with fluorescent lighting for the rooting, growth, and transplant performance of clonal cannabis cuttings; and 2) investigate the effects of temporally-dynamic vs. fixed LED and fluorescent spectrum treatments on the rooting, growth, and transplant performance of clonal cannabis cuttings.
This trial was designed to evaluate the effects of light spectrum on the rooting, growth, and transplant success of clonal cuttings from different cannabis cultivars that reportedly had varying rooting rates. Traditional fluorescent lighting along with five LED spectra, composed of two fixed-spectrum (W and BR) and three dynamic-spectrum (B, B+UVA, and B50) treatments, were investigated. Some of the spectrum treatment selections were based on previous findings in the literature that high proportions of B can promote root initiation and make transplants more compact, whereas UVA can promote root growth and plants resistant to transplant stress. . Fixed-spectrum LEDs have the advantage of infrastructural and logistical simplicity, whereas dynamic-spectrum treatments have the potential for a higher level of control in using spectrum as a production tool to manipulate crop growth and morphology.
The use of different light spectra derived from LEDs were generally as good or better than fluorescent lighting for the rooting and post-transplant stages of clonal cannabis growth..This confirms the viability of transitioning away from older fluorescent lighting technology to more energy-efficient LEDs for the propagation stage of cannabis. All the tested LED treatments can be used in cannabis cutting rooting propagation, although the B and B+UVA appeared to be slightly better in certain aspects.
The authors of this study include Melissa Moher, David Llewellyn,, Max Jones, & Youbin Zheng from the School of Environmental Science, University of Guelph, Canada and .Scott Golem, Elizabeth Foley, Steve Dinka of the HEXO Corporation, Canada. The experiment was conducted in a commercial cannabis production facility in Southern Ontario, Canada.
Dr. Zheng's group has been actively engaged in research on controlled environment
drug-type cannabis cultivation in the last decade. Some of their research results were
published on scientific journals such as HortScience, and some are summarized in
the Handbook of Cannabis Production in Controlled Environments.
The full article can be found on the ASHS HortSciece electronic journal website at: https://doi.org/10.21273/HORTSCI16752-22
Established in 1903, the American Society for Horticultural Science is recognized around the world as one of the most respected and influential professional societies for horticultural scientists. ASHS is committed to promoting and encouraging national and international interest in scientific research and education in all branches of horticulture.
Comprised of thousands of members worldwide, ASHS represents a broad cross-section of the horticultural community - scientists, educators, students, landscape and turf managers, government, extension agents and industry professionals. ASHS members focus on practices and problems in horticulture: breeding, propagation, production and management, harvesting, handling and storage, processing, marketing and use of horticultural plants and products. To learn more, visit ashs.org.
