UV, UV-A, UV-B, UV-C, and Far Red

Happy holiday’s ya’ll. I have been up and down the internet reading everything I can on UV/Far Red lights and I keep coming up with conflicting articles. I know some of you folks use them, so I would like to know from you if there is any advantage that you have seen during your grows. I mean actual results not what I hear stuff please. I am thinking of using some Far Red LED’s when I flip to flower. UV from what I have researched has no factual based proven studies, plus it is harmful to humans, or at least UV-B. The UV running theory is that it triggers cannabinoid productions to protect itself from the UV light but there is no data on this. Would love to hear ya’ll’s story’s.

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Ive done 2 runs with UVA and UVB. I feel like i saw definite results but didnt have anything side by side to compare it to. Last run i used UVA all the way thru veg and flower and turned off the last 2-3 weeks and switched to UVB things got pretty frosty for sure but without a side by side comparison i cant for sure say. I can post the info i know and what ive learned from this forum





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Thanks BigCat, good info.

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I use the California Lightworks UVB fixtures for the last 3 weeks of flowering. I start at a half hour per day, in the middle of the lights on period, and increase it up to an hour and a half over the next few days. There’s no way to say for sure that they help, but I believe they do. I’m always happy with the end results, great taste, smells, and effect.

I also use the 30watt HLG far red bulbs in all 3 of my grows. They come on for 4 minutes right after the main grow lights go off. I haven’t noticed any difference in the time it takes for flowering since I added them, and that was the main reason I got them, but they definitely seem to make my plants grow bigger and faster in early veg.

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Cap, your great, thank you sir.

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The Hlg uva30 12/12 in flower makes for frosty sugar leaves like Crazy. Ive never used the B, or red. Either way, protect your skin when you go in when they’re on! Turn it off, or suit up

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Was reading on this subject also. Saw mixed reports that leaves one confused.

Everything about growing, i look at mother natures way first.

The good uvb is 280-290nm blue spectrum, at what time of the year do we get blu? Spring. During veg?

Why is it considered necessary for potency? Metal halides covered the blue spectrum well, but never used over the yellow orange spectrum in hps for finishing a bud.

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The UVA is very beneficial through the whole 12 and 12 cycle to plant produces trichomes like sunscreen to protect itself the UVB is very harmful to humans as stated above only use it the last few weeks of flower as stated above a little at a time I use UVA 12 and 12 every flowering cycle sometimes I even use it during veg plants love it the UVB however will damage the plant that’s why you use it the last few weeks and there is definitely a difference when using both lights you could use either or but in conjunction they work very nice :v:

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:hot_face: Will do, thanks Clicky.

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Good stuff JJ.

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California light works has 15% off everything right now.

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I have recently bought a HLG 260 FR light, so can’t say anything thing about FR from experience. If anyone is interested in this light HLG has it priced at $249, and the code “frosty” will get an extra 15 % for the next couple days. I am anxious to give this bad boy a try.
As UV goes, I have tried the UVa 20 watt light in my 2x3 tents. The first one was at about 18 inches from the canopy, and at two hours per day it was burning the heck out of the leaves. Next I moved it to my other 2x3 were it was at 30 inches, and started with 1/2 hour and now at 2. This appears to work better. But I have trouble keeping this tent above 35% humidity at this time of year. The UV light and the dry air are making some ugly ass leaves, but the buds look good,
So I would only recommend tying the UV in a 4x4 or larger tent, and keep it at least at 28 inches from canopy.

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@happypappy, did you get your UV lights going?

@JayDawg, since you wanted people to speak from experience. Let me share this that is based in half experience and half ass bro science.
A few years ago, I was waiting on my first tent with LED light. Since at was springtime, I went ahead and started some seeds, and set the little plants on the rear deck for a few days. Started out with them mostly in the shade, and then moved them daily so that they got more sun for about six days. I moved the plants into the new tent, and things went very well from there. Since I didn’t know any better these plants grow about four colas within about 10 inches of the 130 watt light. There appeared to be no damage to the plants. It now occurs to me, that these were the most light tolerant plants that I have ever had. The three plants produced 12 ounces, and this was a benchmark that I have until now just recently repeated.
So my thinking about UV has evolved to this, and may help explain why it is hard to get thumbs up or down on UV.
I believe that exposure to UV gives the plant a slight genetic change that makes it protect itself and be more tolerant of excessive light. I now also believe that you can trigger the change by using UV early in veg, and this change in genetics will last the life of the plant. If this is correct, you could get the the benefits of UV during veg, and not use it during flower and risk it’s damage.
I am thinking in a near future grow. I will try introducing the UV for only a two week period during early veg. Then switch to the FR light after the second week of flowering.

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You can grow fire without any of this. Go to the studies using scientific method and value the data appropriately.

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@dbrn32, sounds like you are trying to discourage me, from doing my own dumb ass experiments. You are not the first, who have tried to save me from myself.
But seriously, I do try and look up this information on line, in order to weed out the real facts. But after a short time it all becomes confusing and contradicts it’s self. So I end up using this info as a guideline, and my end results become my grow facts. This ends up being my ever evolving techniques.

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Ive added uva 30w hlg xl on my last grow. Made it slightly more frosty but minimal. It is nice to try to achieve a extra percent or two on potency but i would put money else where in your grow unless everything else is on par.

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Nicely put. I’m firm believer that anyone can spend their money however they see fit. I’m also usually pretty willing to share my opinion anyone can take for whatever they want. The issue you’re running into is these results aren’t repeatable from one study to the next. To me, this says everything it needs to. One very popular study to the uv crowd states something like a 5% increase in thc content with uvb. But actually reading the abstract showed the tested thc levels on non uv plants at something like 20% thc and the plants exposed to uvb tested at 21% thc. This is indeed a 5% increase in thc but not same increase as going from 20% thc to 25% thc like some want to believe.

This is very similar to telling someone they need more light and their response is that they’re focused on quality not quantity. The problem with this idea of thinking is that quality and quantity are both mostly driven by the same things. I like @Poseidon1’s approach here. If you’re bored or have a bunch of money burning a hole in your pocket, then by all means have at it. Just don’t expect a lnock your socks off difference.

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@dbrn32, hey, thanks for all your advice, and help, that you give to all on this forum.
What are your thoughts on the HLG lights with the added FR?

Which lights specifically are you asking about? Most to my knowledge don’t include any far red, they use what is typically referred to as photo red or deep red around 660nm.