Moe.Red said:

Why green?

Frontiers | Photosynthetic Physiology of Blue, Green, and Red Light: Light Intensity Effects and Underlying Mechanisms

Red and blue light are traditionally believed to have a higher quantum yield of CO2 assimilation (QY, moles of CO2 assimilated per mole of photons) than gree...

www.frontiersin.org

Probably a bad idea for photo plants unless you are adding it to the lights on schedule, but not at night!

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this is missing the point, photosynthesis is an entire different topic than photomorphogenesis.
the former is driven by chloroplasts and the latter by (much more sensible) photoreceptors.
plants don't wake up from photosynthesis but because phytochromes get reverted by PAR light. But not all color get absorbed equally:

You best not advise "white light" in the dark period, because usually these diodes peak at ~630nm and will still have a huge area under the curve for the Pr absorption max at 660nm.
Which is the reason why any generic growlight that is wrong-phased + ungrounded can reveg plants when the diodes dim in the night (unknowingly)

Still, a green monochromatic light can also lead to reveg due to various effects that convert green to red when the photons get scattered.

N1ghtL1ght said:

this is missing the point, photosynthesis is an entire different topic than photomorphogenesis.
the former is driven by chloroplasts and the latter by (much more sensible) photoreceptors.
plants don't wake up from photosynthesis but because phytochromes get reverted by PAR light. But not all color get absorbed equally:
View attachment 1215602
You best not advise "white light" in the dark period, because usually these diodes peak at ~630nm and will still have a huge area under the curve for the Pr absorption max at 660nm.
Which is the reason why any generic growlight that is wrong-phased + ungrounded can reveg plants when the diodes dim in the night (unknowingly)

Still, a green monochromatic light can also lead to reveg due to various effects that convert green to red when the photons get scattered.

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Thanks for your post, you are speaking my language. If there is something I can learn from you I'm looking forward to doing so.

Let's get on the same page tho. First, I did not advise white light, I advised no light. The point of my posts is that plants need to stay dark and to adjust your grow to the plants, not to find a cool headlamp that gives you a false sense of safety.

Second, the thing about green is it is it is actually absorbed deeper in the plant tissue than red or blue. Please read the link I posted for details. Your chart is very misleading in this regard.

I do have to ask - you have very few post here and a name of Night Light. I just have to ask, are you someone who sells these lights?

Now on to more science:



Start at 27mins for good background, but at 29 mins Dr Bugbee talks about how cannabis is "Exquisitely sensitive to light pollution, and just a little bit will cause problems with cannabis."

He calls it "Reagent grade darkness."

lvstealth said:

better to adjust their daytime. just change the hours they are dark by a little either way

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This is a much better option than putting any light in dark periods. Green or otherwise. And costs nothing.

My thesis is green is not some silver bullet that protects plants from the ill effects of light pollution. Your money can be spent better in other areas, such as adapting your space or timings so that you do not need to enter it at night period. If you want to debate that, I'm your daisy. But I am not going to defend things I did not say but you inferred.

Right on! Going to browse Amazon today. Thanks for your input!!

Not intending to interfere with their sleep, just want the option if I need it.

Moe.Red said:

Thanks for your post, you are speaking my language. If there is something I can learn from you I'm looking forward to doing so.

Let's get on the same page tho. First, I did not advise white light, I advised no light. The point of my posts is that plants need to stay dark and to adjust your grow to the plants, not to find a cool headlamp that gives you a false sense of safety.

Second, the thing about green is it is it is actually absorbed deeper in the plant tissue than red or blue. Please read the link I posted for details. Your chart is very misleading in this regard.

I do have to ask - you have very few post here and a name of Night Light. I just have to ask, are you someone who sells these lights?

Now on to more science:



Start at 27mins for good background, but at 29 mins Dr Bugbee talks about how cannabis is "Exquisitely sensitive to light pollution, and just a little bit will cause problems with cannabis."

He calls it "Reagent grade darkness."



This is a much better option than putting any light in dark periods. Green or otherwise. And costs nothing.

My thesis is green is not some silver bullet that protects plants from the ill effects of light pollution. Your money can be spent better in other areas, such as adapting your space or timings so that you do not need to enter it at night period. If you want to debate that, I'm your daisy. But I am not going to defend things I did not say but you inferred.

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Hello, no I'm not selling anything I'm rooted into science & reading, esp. photobiology & plant physiology. I know most of Bugbee's work and he is generally spot on. Perhaps I should have rephrased that to "if you ever have to use a night light, then best use a green one"
It's just that the plants sensitivity towards blue or green is much greater and I think Dr. Bugbee refered to white light in that video as opposed to monochromatic light.

Actually, the breaking of the Pfr hormone buildup during the night can be countered by far-red 730nm - there are many studies done on plants showing this. Even Bugbee made a recent study regarding this, continous FR (or IR) light during flower, though it had no beneficial effect, it actually delayed flower when being overdone.

And you can see from the above posted absorption spec that this region between cyan & green also rather stimulates Pfr - thus, antagonizing the Pr "lights-on" effect.

That said, if Cannabis plants are already grown large & advanced in flower than a short exposure to a dim light - even light - won't throw it off course.

N1ghtL1ght said:

Actually, the breaking of the Pfr hormone buildup during the night can be countered by far-red 730nm - there are many studies done on plants showing this. Even Bugbee made a recent study regarding this, continous FR (or IR) light during flower, though it had no beneficial effect, it actually delayed flower when being overdone.

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I was aware of this and have multiple Far Red LED fixtures and a Far Red PPFD meter from Bugbee where I have done some personal testing. I think we are just really starting to understand all this. Pretty interesting to me too. Love to talk to you about that in a different thread - outside the scope of this one.

N1ghtL1ght said:

That said, if Cannabis plants are already grown large & advanced in flower than a short exposure to a dim light - even light - won't throw it off course.

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So this thread started with a grower who was looking to move maintenance to dark period. Then another stepped in and said he used his all the time and gave links. To me, that is a basic misunderstanding of what we are dealing with here. Honestly I think you and I are the only ones looking at the actual science on this thread, so what I am trying to do with this post is to make this easily understandable for the next grower that comes along with the same question 2 months from now and finds this thread. I don't think I am doing a good job because people just want a quick fix delivered in a brown box with a smile on it, not to understand the real deal.

I agree that " Cannabis plants are already grown large & advanced in flower than a short exposure to a dim light - even light - won't throw it off course." however that is a lot of qualifications to that statement that new growers are just gonna fly by. Perhaps what I should have said from the start is

Keep the plants in full darkness at night as close to 100% as possible.
If you must go in, do it fast with minimal lighting, whatever is handy.
If you find yourself doing this on a regular basis, you are making a mistake.
No product you can buy at Amazon will give you night vision that the plants will ignore.

I appreciate everybody's input greatly. The intention was not to spark a debate but rather get a recommendation just in case. Cheers all!

Nothing wrong with debate! I appreciate an intellectual challenge, it's how I learn. As I mentioned earlier I got schooled by Aqua Man on this green light issue - I was dead wrong and now I better understand the whole. Just gotta be open to being wrong and stay adult, and a little friction can be a good thing.

I just fitted a room with the new Gavita SL2 fixtures. Each fixture has 3 green LEDs that cast a green glow onto the plants when the lights are off. I've also noticed other manufacturers including green leds on their fixtures.

mikeross said:

I just fitted a room with the new Gavita SL2 fixtures. Each fixture has 3 green LEDs that cast a green glow onto the plants when the lights are off. I've also noticed other manufacturers including green leds on their fixtures.

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Is this what you are referring to?

Status LED​

The Status LED provides information about the operating status of the ballast. It senses connection with the controller, indicates a starting lamp, end of life, over temperature, too high input voltage, too low input voltage and it even has a memory for alarms.

Moe.Red said:

Is this what you are referring to?

Status LED​

The Status LED provides information about the operating status of the ballast. It senses connection with the controller, indicates a starting lamp, end of life, over temperature, too high input voltage, too low input voltage and it even has a memory for alarms.

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Yes it's a status light but lights up green when the fixtures turn off.. This is the fixture, you can see the 4 green leds in the photo below. I spoke with gavita regarding it and the rep I spoke with said everything is OK, they are suppose to all stay on lights off, when in ext. mode, when using their controller.

mikeross said:

Yes it's a status light but lights up green when the fixtures turn off.. This is the fixture, you can see the 4 green leds in the photo below. I spoke with gavita regarding it and the rep I spoke with said everything is OK, they are suppose to all stay on lights off, when in ext. mode, when using their controller.
View attachment 1216226

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I’m open to ideas on why they would do that. I can’t imagine most growers want lights on 24 x 7 regardless of the color?

I did a search and couldn’t find anyone mentioning this issue. Should it only be on when powered on and you have an issue?

Moe.Red said:

I’m open to ideas on why they would do that. I can’t imagine most growers want lights on 24 x 7 regardless of the color?

I did a search and couldn’t find anyone mentioning this issue. Should it only be on when powered on and you have an issue?

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I'm looking into it a little more now. From what I read these green lights flash will flash if there is an issue with the fixture... which lights flash and for how long indicate the problem.

It does sound odd to me that they are on 24/7. I'm gonna put in another ticket with gavita and ask them again.

Moe.Red said:

And here is my point - you might as well use full spectrum for that so you can actually see the plants and diagnose issues, because green light is no better for sleeping plants.

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Surely ppfd or light intensity play a massive part of that ? I recently let someone babysit a room for me and I flipped to 12 12 the day I went on holiday. Timers were on lights no issue there but when I get home, the actual normal ceiling bulb, all 30w of it had been left on 24 hours a day ! So in thinking shit these are fucked , but they flowered perfectly fine the same time and yield as usual. And that's with the first 11 days being under 24 hour light essentially as the room light was on, but growlights on 12 hour a day . I've got one of those led striplight on a rolls running round my room and am constantly in there tinkering under greenlight and they are probably 10w, never noticed absolutely any harm just because it's a lit room I'm not sure the plants can even bother trying to do their processes under such dim conditions