I used veg light in stretch as it keeps plant hieght lower in my room , after stretch I switch to a flowering light : )
makes a big difference : )
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I for one care.
Others may too, seems you do not… 
No, to make lanky plants short…LOL
To reduce stretch, you know that thing everyone seems afraid of, that some desperate folks will even buy bushmaster ect. and spray it on their plants to keep em short.
Seems to be a thing in certain circles, other than your own of course.
There is a ton of folks asking the question “How to stop stretch”
It is hard to believe you have not heard of this concept before.
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Thanks for that, some folks here seem to think I am just spewing nonsense.
This is proven science folks.
Good solid info : )
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Grow plants that don’t stretch too much in the first place.
FYI I’m running a blue spec right now in flower and the squat plants are squat as they should be and the lanky plant is lanky as it should be.
The squatter plants will be more squatter and the lankier plants less lanky than what they would have been if they been under a flowering light
Plus less buds more leaf under blue in flowering
Veg light for veg and stretch flowering light for after stretch is best
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Are you talking blue spec HLG LED fixture?
If you are, I looked at the spectrum of that light and I believe I found the blue spec, actually had less blue output than the diablo boards did.
That is something that should be considered here.
Yes but where is this pure blue light coming from? Do you put gels over your bulbs?
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I would not suggest that personally, although it may in fact work, dunno?
This could be one possible source, with all blue diodes in the proper wavelength.
Summary:
Studies have shown that exposing plants to high levels of blue light can result in reduced stem elongation and increased branching, leading to a shorter plant stature.
This effect is thought to be due to the role of blue light in the regulation of the hormone auxin, which plays a role in stem elongation and branching.
Yes I’ve heard this before but I don’t know of anyone who has hung up a blue light as you mention in this manner.
Anyone?
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I think maybe ol’ Bruce Bugbee did it, but I would need to check to be sure.
There have been a number of experiments done on blue light and cannabis.
I do not see the need for knowing one of these folks on a personal level.
What would that prove?
The science is sound on this topic.
If you still doubt what I am saying is the truth…
A side by side experiment would surely show there is a difference.
Feel free to prove this to be incorrect, if you wanna take the time that is? 
So…nobody.
The onus is on you to prove your claims. I make my own ridiculous suppositions and I will fight to the death to defend them.
Hmmmm?
Not really, science has a way of speaking for itself.
Personally, I am very sure the science behind this is sound.
I have done anecdotal experiments that were conclusive enough not to need a proper side by side to be sure.
@ifish has done something similar himself.
I am just here to share the knowledge with you and other fine folks here at OG.
If you have chosen to believe your own ridiculous suppositions over the real science provided to you here and you are good with that, so am I …LOL
But
If you really want to see the results for yourself, cause that is the only person you will believe, then with the info I have provided you have the means to do too that if you wish.
The rest is up to you, I just provided the facts.
I do not feel the need to make sure you know the truth, that should be placed in your hands.
Again this science is very solid and you are very free to ignore the truth if that is what you wish.
I can assure you the info I have provided is pretty dam solid and is also well known to be true.
Best wishes
shag
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Right back atcha dawg
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Alrighty then…LOL
@Foreigner
Please forgive me, I just realized we had had that discussion before.
I did not mean to rekindle an old fire there. 
I am getting old and the memory is slippin’…LOL
Anyway
I was going over some notes, and found some more info on this topic and wanted to add it to this and another thread.
This is not directed at anyone …
Here are some notes from a guy they call spurr, pretty smart this one…
This was written by Spurr
Thank you to him for sharing this with us all!
Some plants like other plants near them, like companion planting. But in general plants don’t like to touch other plants because that means they would get shaded by other plants which makes them ‘compete’ for light. This is a major reason plants stretch, it has to due with the amount of red light inner canopy in relation to far-red light inner canopy. Far-red light penetrates into the canopy well (passing through upper canopy leaves), but red light does not. The ratio of red to far-red light inner canopy is a major trigger for plants to grow (stretch) because the greater the far-red light and the less the red light inner canopy makes them think they are being shaded. It’s like two people fighting over food…
This topic is one reason plants can stretch more under traditional HPS than traditional MH. Because HPS has more far-red, which means HPS would provide a higher red/far-red ratio inner canopy vs. MH which would provide a lower red/far-red ratio inner canopy (i.e. amount of red and far-red would be closer under MH than under HPS).In terms of red/far-red ratio inner canopy affecting plant stretching I think growers who fit the following descriptions need to be concerned:
- Those who have dense canopies of plants taller than a few inches (ex. > 10")
- Those who have poor lighting in terms of a lamp with or without a reflector providing direct light (esp. traditional HPS) that is not well dispersed over the canopy.
- Those who have light sources with lower intensity (ex. =< 250 watt HPS).
- Those who have a LED array with many of the red diodes in the far-red range of > 700 nm, specifically ~720-740 nm.
- Those who use LED arrays with diodes having narrow irradiation footprint. This has to due with the direct light provided by the diodes and how direct light irradiates inner canopy less well than diffuse light.
The ratio of red ® to far-red (FR) light in the day under the sun when it reaches plant canopies is usually R:FR of 1:1. The R:FR light ratio below leaves can be around 0.15 [1][2]. The difference is due to how leaves absorb red light very well, but absorb far-red light less well. Much of the far-red light is transmitted through the leaf into the lower canopy. Red light has much lower transmittance rate through leaf. That means more far-red light will reach inner canopy when the top canopy is dense. In the early am and pm the ratio of R:FR is reduced due to a reduction in red light and increase in far-red light.
Red and far-red light affects the plants’ phytochrome responses, red light phytochrome is termed Pr and far-red light phytochrome is termed Pfr
There are a few things that affect plant growth and stretch, the first one has as much of an effect on stretch as does R:FR. We can tweak the following to reduce internodal elongation and plant stretch while keeping plant growth rate high [2][3][4]:
- (stretch) “DIF” is the difference between averaged day time temp (esp. in early morning hours) and average night time temp. If the DIF is positive then the plant will stretch more. The greater the positive DIF the greater the stretch. A zero DIF means less stretch and a negative DIF means much reduced stretch vs. a positive DIF. The reason DIF affects plant growth is DIF affects levels of GA3 in the plant early in the AM. Less GA3 means less stretch and negative DIF means less GA3.
The most efficient way to control DIF is to keep the first 3-4 hours of ‘day’ cooler than the rest of the day. This is called early morning “DROP” (aka “DUMP” and “DIP”). Ideally a DROP with a DIF of -5 to -10 (Fahrenheit), or at least zero, for pre-flowering would be employed. Long term negative DIF can hinder plants and biological process; the more negative the greater the effect. Long term zero DIF using DROP for the whole grow will make a very compact plant. I plan to carry out lots of analytical testing on this method with cannabis in the future.
Using a room A/C and heater a grower can trivially setup their grow to use a zero DUMP or -5 or -10 DUMP, etc.
-
(stretch) Too much P (and N) will increase the shoot to root ratio making greater internodal length and stretch. This is why not increasing P during pre-flowing can help, besides, P is overused anyway. Cannabis doesn’t need nearly the level of P that most conventional growers apply (e.g. Lucas formula).
-
(stretch-growth) SAR inducement via. shaking/touching the plant and/or leaves, using chemicals, etc. Any of those can cause SAR in a plant that can increase plant stretch. Thus manhandling the plant when watering or trimming may or may not be a good idea (depending upon grower goals).
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@ifish I believe you know who spurr is???
He was from ICrag
This was from him, I knew there was more to that statement and I could not remember all the specifics when you asked but I found this today.
The most efficient way to control DIF is to keep the first 3-4 hours of ‘day’ cooler than the rest of the day. This is called early morning “DROP” (aka “DUMP” and “DIP”). Ideally a DROP with a DIF of -5 to -10 (Fahrenheit), or at least zero, for pre-flowering would be employed. Long term negative DIF can hinder plants and biological process; the more negative the greater the effect. Long term zero DIF using DROP for the whole grow will make a very compact plant.
Some good info about why the percentage of blue photons is important to plant height.
Find that info at 39 min in on this video.
Maybe my boy bruce can better explain things here. 
Blue light regulates the opening and closing of stomata.
Stomata are the tiny pores that allow gas exchange and CO2 intake.
This gas exchange is critical for bringing in the CO2 needed for photosynthesis, and also for cooling the leaves through the release of moisture.
This action helps to keep leaf temperatures lower.
For that reason, most sole-source lighting fixtures include at least some blue light.
I imagine it’s more due to the lack of red than the presence of blue. Stomata guard cells are triggered to open by very low levels of blue wavelength lighting (like <2 umol), but only so much.
The other factor that plays into lights’ control over plant stomata opening/aperture size is red light, which requires much higher intensity levels of red to reach saturation and be as open as possible.
So, if it’s only blue light with very little red, you are getting the guard cell response but not the full opening that requires relatively-intense red wavelengths, as that saturates near the same PPFD as photosynthesis itself.
Can veg-ing under blue light increase yields?
It’s important to give your plants the blue light especially in veg.
With blue light plants show robust lateral growth without extension.
Shorter plants with better root growth will be better prepared for flowering, therefore, increasing yield.
What’s more, plants grown with a spectrum that’s rich in blue have thicker, darker leaves than those grown without blue light, and that prepares them for a robust flowering period.
With the HLG boards we still get a good amount of blue.
But I think it is not the best blue to red ratio for veg.
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I don’t know spurr , I just thought of all that off top of my head from your writings
I love to ponder and over think things
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Well, looks like you were right on…nice work there. 
As do I, smokin’ and thinkin’ is what I do best…
Well I got the smokin’ part down pat anyway…LOL
I had not mentioned stress as a cause of stretch but I did see spurr mention it above so I thought I would now.
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