The UV light stays on all the time from the sun. If you’re in flower why are you only running it for two hours?
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Thats the recommendation from all the sources I’ve been reading and the manufacture. Duration and frequency vary but everyone I’ve researched say to only run in short periods to keep from burning plants. Supposedly a little is good but a lot can actually be detrimental to growth and quality.
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That’s interesting. Most of the growers I know across three different forums run them from start to finish or when the lights are on in flower with tremendous trichomes production and no ill affects.
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It’s my first time using UVB so starting with a little and seeing what happens. Would be willing to hear advice from anyone currently experienced with it from here.
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I’ll tag @hellraiser . He’s really good at explaining things and I’m pretty sure he runs his UV light all the time.
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Great I appreciate it. All ways willing to learn from experienced growers. I’ve read @hellraiser post and know him as a respected grower. Looking forward to what he has to say. Thanks
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Yeah that is the recommended usage with UVB, a couple hours a day for last few weeks of flowering. I run UVA instead of UVB which can be run for all of flowering and even in veg if desired. UVB is much more damaging to the plants (and people) so needs to run for less time.
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Thanks for the input @hellraiser and @happilyretired. I appreciate it. Makes me feel better that my research was confirmed by a known grower here on GN. @happilyretired I appreciate your input as well. We are all learning everyday I hope.
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I’m curious about your choice to run UVA? Most everything I read about it was since our atmosphere blocks it out it’s not necessary for plants. What has been your experience with it?
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Getting some nice color to. 
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UVA is actually the most abundant and least harmful of the ultra-violet spectrum, 95% of the UV that gets thru our atmosphere is UVA, we are hit with lots of UVA every time we go outside during daylight.
Our atmosphere completely blocks UVC (a good thing as it’s extremely harmful to plants and animals) and blocks most of UVB (less harmful than UVC but still dangerous).
I like that UVA is not as harmful to me as UVB so I don’t have to worry about turning it off when working on the plants, while it still does a decent job of stressing the plants for more trichome production as a defense mechanism. Plants I grow under UVA show denser trich coverage and possibly a small boost in THC.
I also like that good UVA lamps can be had in LEDs at this point rather than the flouro tubes for UVB. The LEDs having better penetration over a low watt flouro tube.
It’s also quite telling in my opinion that the better USA light companies like HLG, ChillLED, and Gavita only make UVA lamps and not UVB.
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Still learning. I love it. I bought the lights last year and installed them and use them on my last indoor, but I just did it because everyone else was.
… now I learned why… perfect…
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I think I have the same lights as you. I think there 30 W HLG’s that clamp on their big lights.
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I’ve used UVB lamps in the past with HPS lights and they do help stress the plants as well but have to be more careful with them. I once saw a bald headed friend of mine get a wicked sunburn on top of his head after forgetting to turn off the UVB lamps before a hour long defol session.
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Yep, I use the HLG UVA30 mounted to a HLG 550 Rspec in my flowering tent and free hanging between a couple HLG 135 Bspecs in my veg tent.
Even in veg, the UVA makes the leaves sticky with the extra trichs the leaves grow.
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@hellraiser I obviously mixed up UVC and UVA. Really appreciate you explaining all that. I’ve read about numerous ways to use UVB and they all say just short duration but really vary on for how long per day and when to start. This being my first time using it I just picked the system that made most sense to me. I started at week 5 of flower for 2 one hour runs. At week 7 I’ll go 3 one hour runs And at week 8 go to 4 one hour runs. Only time will tell now. I am very careful about being in tent while its on. Thanks again!
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