After our preliminary study of supplmental UVA on Cannabis, we saw the promising results: doubled yield/twice bigger buds, increased trichome, stronger smell (probably due to increased terpenes), and 100% reduction on Powdery mildew.
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Hi Rich, UV can help increase yield when used with a high PAR grow light. Hard to say how much UV is exactly needed at this moment, but it is about a balanced spectrum with light at 400-700nm. UV-B:UV-A:PPF in sunlight is approximately 1:23:270, according to the publication from Caldwell and Flint, 1994. Reported UVB intensities and doses are from <1 mW/m2 to 1600 mW/m2 for intensity, and <1 KJ/ m2/d to >100 KJ/m2/d). in Our case study, we used UVA at 7.8W/m2 with dose of 111KJ/m2/d. The key things are you need to determine the most effective UV in your growth condition with your strain, because UV interact with other environmental variables and I believe genotypes as well. We are going to study UV on more strains at different growth environment. So hope I can have a precise recommendation on the intensity and dose in the near future.
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I started growing with UVB around 2010 and have sworn by the ability of the spectrum to significantly increase the quality of the finished flowers. Why do you think it’s taken so long for research to be conducted on UV light and cannabinoid, terpene and flavinoid production?
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I think main thing is because university does not have funding and license to do research on Cannabis. UV research is expensive in term of equipment, told by professors. But now with medicinal cannabis legalized nationwide and whole legalization package in Canada, I think there will be more researchers get involved in UV studies in Cannabis.
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Combining LED’s with LEC’s has proven to be the most effective means of providing supplemental UVB light with high PAR overhead light. I love the results!
Have other @mastergrowers, @GrowOpEmployees, or @growopowners used supplemental UVB? What were your results?
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We can only hope! There seems to be a huge knowledge gap in this subject in our industry.
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Can you share a little about the anti-pathogenic properties of UV light that you have studied in your research? How does UV light affect mold/mildew spores?
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Yes, and as a horticulture lighting scientist in industry, part of my job is to bridge this gap between academia and industry.
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Nick, can you share with us how you combine LED and LEC for your lighting strategy? Do you have your LEC on for 12 hours per day from veg to flowering?
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I like to run one LEC with a 10,000°K bulb for every three LEDs in my lighting array.
I do not use UV light in vegetative growth. I generally use the UV only during the final three or four weeks of flowering when the flowers are bulking up and the flavinoids and terpenes are maturing. I have in the past used the UVB for the entirety of the flowering cycle (12 hours per day) and experienced no observable adverse effects in the plant system. The finished flowers are absurdly packed with trichomes and the flavors of the flower and extract are outstanding.
I highly recommend any grower growing for extract implement UVB light as part of his or her overall lighting formula.
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So we see no PM spots on the plants treated by our UVA light vs. some spots on the control plants. A Norway research group also reported 90-99% reduction of PM in cucumber, strawberry and rosemary. A USDA group reported enhanced shelf life and no mold (Botrytis ) of strawberry when treating with UVB 9 days after stored in refrigerator vs. mold growth after 6 days in the control.
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Awesome! Thank for sharing.
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Have produce packagers and shippers caught on to the anti-mold/mildew properties of UV light? It seems UV can really transcend the cannabis industry on to so many other potential commercial applications! I think of the massive amounts of produce that goes to waste just because of mold/mildew. It seems the UV light could significantly increase shelf life!
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I will present a similar UV topic in another conference in a couple of weeks. After that, I might be able to share my slides with you.
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I also want to mention the increased secondary metabolites under UV treatment. Except THC and terpene increase, I think there is a potential to increase flavanoids which contribute color and anti-inflammatory functions in cannabis according to the results in other crops like apple, tomato, lettuce. I am very interested in conducting this research as well.
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We often associate UV light with cancer. What steps are you seeing growers and facility owners take to protect their work force?
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Peter, I appreciate you sharing UV knowledge with me as well. I are one of great people who introduced me into the UV world. Will I see you in the Big Idea UV conference in two weeks?
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What is the expected effective longevity of the suggested UV lamps?
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Great question! First, UVA is safer than UVB radiation when used in the same amount. Longer wavelength UV radiation (UV-A) accounts for up to 95% of the solar UV radiation that reaches the earth’s surface.
Although safer than UV-B and UV-C, I do NOT suggest workers stare at it and/or stay under the fixture for too long while the UV-A is on. I recommend only using this light source for a couple hours per day when there is reduced foot traffic in the grow area and ideally with protective glasses.
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When launch our UV LED product, we will recommend a safe distance and duration for workers.
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