This is the prevailing wisdom and I’m not going to tilt at windmills but the number one factor in stretch is genetics. Does blue light inhibit stretch? Probably. But it isn’t going to make a lanky plant significantly less lanky.
Just for example, 2 seeds from the same pack grown under 4000k
Different phenos obviously but a pretty significant difference between the stretch of the two.
I agree. I’ve grown many plants in the same conditions and it’s all about genetics
I was actually playing around with slowing the stretch over the last week as I have this one cultivar that’s going hardcore for a damn 3x stretch or something it’s nuts and I did not have any intention of scrogging this run so I can access and move things around but if this doesn’t stop ASAP. Apparently I’m running a scrog again ffs. Who would have thought a Bubba cultivar would have a 3x stretch
Always enjoy your threads and the info you share Shag 
It is not so much a fact that blue light inhibits stretch.
It is more of how a ratio of red to far-red light will cause stretch.
It is a situation where the plant thinks it is in the shade so it will bolt or stretch to get into the light.
This can get a bit technical, and unless written from my notes their may be some error.
So I will add more on this topic when I can.
Adding an imbalance of far-red to red and you will surely have some stretchy plants that would have been short in a natural environment.
So light can play a huge factor in stretch, especially when you speak of shade avoidance.
You may ask, what is shade avoidance?
Shade Avoidance
Shade avoidance responses include elongation of stems and petioles, altered flowering time, and increased apical dominance, which elevates the leaves toward light.
The plant uses natural hormones to grow into the light.
Hormonal regulation in shade avoidance. Auxin, Gibberellin (GA), Brassinosteroid (BR), Karrikin and strigolactone (SL) are all involved in shade-regulated stem growth.
Ethylene is required for shade-induced petiole elongation.
https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/shade-avoidance
To be clear this statement is mostly correct.
Please forgive me if I am coming across as harsh.
That is not my intention.
But the reverse can be done for sure.
You can easily take a short stocky plant and make it very lanky with light.
Also
Just blue light without red and far-red will make plants abnormally short.
So you can control the lankiness within reason with light, even with super-stretchy plants.
Also, you can manipulate plant hormones to make the world stretchiest plant, short and stocky.
And vice versa.
Peace
Shag
It’s all good man.
There was somebody on here who I don’t remember who hit a plant with a hormone I don’t remember and the thing stretched itself into oblivion. Quite amazing.
Yep , this would do it for sure!
Gibberellin (GA)
I have no use at all for this hormone in cannabis.
It is also know as the masculine hormone in cannabis.
We all know where that leads us…LOL
If shade => blue there is apparently a contradiction between both sentences 
, does it stretch or not? It’s an interesting info I would like to know, thanks … 
I have grown a plant in full shade and it didn’t stretch. Barely grew at all in fact.
Bad genetics … 
I am not sure what you mean here…
Shade is equal to or less than blue?
Please explain.
Thanks
Shag
Me or the plant? 
Yes, that makes sense, but did you grow a plant in the dark with only red and far red light?
Give that a shot.
You will see what I am saying.
Both! 
I was associating red with 
and blue with dark-shade, perhaps it’s a misconception …
I am not going to do this but I would be very interested to see your documentation.
What are you looking for when your looking at Pk Def?Like lower fading leaves or crumbly lower leaves from plant eating leaves to make nutrients to make more leaves causing a mobile nutrient issue?
Yes exactly. Just a little browning of the tips at the bottom.
I’m finding out that rootbound plants cause this issue too and sometimes it masks other symptoms.I’ve started popping the plants out of the pots and looking at the roots more if it’s all warped wrapped around the bottom of the pot I’ve been not only repotting but BOG double potting into a container that is at least half a size bigger and putting the previous pot 2 inches into the next taking care to let root solidly and not bump around the new and previous pot to cause root damage and set those roots deep and use as much vertical up down space to get taller bushier plant.I love that double pot method it’s flawless.
I’d bet money that these root bound plants are showing deficiency symptoms because the feed hasn’t been bumped to accommodate the size of the plant. I routinely run in pots that are “too small” and find it’s fine as long as you estimate feeding requirements correctly.
But your mileage may vary 
(I’m overdoing it on my current grow and am trying to correct it)
