7th Inning Stretch.....Everything you wanted to know about stretch and more

[shag]

You may ask…
Is all “stretch”, or just excessive stretch bad?
Or is it just at certain times it is tolerable and intolerable otherwise?
How do you define what is usually normal growth and what is stretch?

Well stretch is really a good thing, it is excessive stretch that can be bad.

When internode spacing is too large our top bud looks stretched out.

When we have just enough stretch we have a perfectly formed cola over 1 foot in length…ish…

Also when we get too much stretch our top bud is growing into the light and the buds just below get less than optimal light.

Phosphorus

High phosphorus promotes stretch while low phosphorus inhibits stretch.

If you bump up phosphorus when the plant is setting the nodes then all you’ll do is promote stretch via stem elongation.

Phosphorous, as well as potassium and iron starvation, causes increased ethylene production which in turn antagonizes gibberellin action.

The net effect is reduced stretch, lateral root branching and root hair formation, and increases the bud/root ratio too.

But nutrient starvation obviously stunts growth and redistributes the plant’s energy to the roots in order to increase active nutrient uptake and that may be counterproductive with regard to the redistribution of energy into flowering.

The key is to run low P during the stretch cycle only - so roughly first 2 - 3 weeks of 12/12.

Once nodes have set and stretching slowed completely you then bump up P to about 60ppm (although I believe this figure can come down to around 50ppm.
Maybe P as low as 20ppm during stretch, depending on the growth habits of the strain.

This action is not necessary but helpful.

But I wouldn’t recommend this to others yet unless it was just one plant in a side by side test.

I feel we should just keep low P a constant unless we are deficient.

But definitely don’t bump P before stretch like we have been told to do.

The current studies are showing low P reduces stem elongation, but there’s still a way to go in establishing just why this is.

Side note here:

Scientists recently discovered that simple sugars break bud dormancy - it’s long been believed that it was IAA playing the key role but now research has shown it’s primarily related to sugars and the down regulation of IAA plays a secondary role in the process.

IAA plays a secondary role.
It’s second in command but equally important.

I have not found the proper way to use this to our advantage as of yet, but found it in my notes and thought it worth a mention.

[shag]

Morning Dif
AKA temperature difference.

When possible use a zero to -5 DIF during pre-flowering by heating your room during the night.

If you need to use heat during the night, it should be equal to, and/or just above, temp during day.

So here is an example, night temp is ~75-83’F and day temp is ~75-78’F. give or take a few degrees but never falling below 75’F

Once the stretch period of pre-flowering is over change back to a +5 to +10 DIF and then late in flowering change again to a +10 to +15 DIF to increase leaf/bud color via affecting (increasing) anthocyanin (a type of flavonoid).

[Foreigner]

I feed veg ferts until I start to see PK def about 2 weeks into flower then switch to flower ferts.

Not sure on a stretch side by side but I’ve done plants that barely stretch and plants that stretch like crazy the same way.

[mainerJ]

good info people. i have been wanting to ask a stretch question myself. when i do my winter indoor grow i have always vegged under mh and then move to hps for flower. it seemed i got noticeable stretch doing it this way. this past winter i vegged and flowered under hortilux super hps. i had 6 or 7 different strains going so i know it was not genetics but for some reason when i flipped then to flower there was very little stretch in any of them? any one ever have a similar experience like this?

[shag]

@mainerJ

i have always vegged under mh and then move to hps for flower. it seemed i got noticeable stretch doing it this way. this past winter i vegged and flowered under hortilux super hps. i had 6 or 7 different strains going so i know it was not genetics but for some reason when i flipped then to flower there was very little stretch in any of them? any one ever have a similar experience like this?

I need to add some more about red light and far-red light and the importantce of the ratio between red and far red.
There is also something called shade avoidance to consider with far red light.

What you have described makes perfect sense scientifically.
MH is very blue, with that you get very little stretch from blue light.
HPS is very red and you get lots of stretch from red light.

When you veg under HPS you get stretch all the time so it will seem less dramatic when you flip the light.
Plants grown under blue light(MH) will be shorter than plants grown under red light(HPS)

Also
I feel that when you/we change the light from 18 hrs to 12 hrs abruptly, the amount of darkness the plant gets is increased dramatically and this too causes some internode stretching.

[Lobstah]

Would stretch be reduced if instead of going straight to 12/12, it was more gradual?..say a week at 20/4, then a week at 16/8, and then going to 12/12?

Lob

[shag]

@Lobstah

Would stretch be reduced if instead of going straight to 12/12, it was more gradual?..say a week at 20/4, then a week at 16/8, and then going to 12/12?

I have not done a real scientific experiment, but my personal anecdotal findings are…
Yes, it should have an effect.
It is best to experiment with your particular cultivar/strains, as I have found this is variable amongst different cultivars/strains.

The trick is to keep all of these needed parameters in check to increase the chances of reducing stretch as much as needed.

[shag]

I have a timer that will allow a time reduction of 15 min. at a time.
I just reduce 15 min. every other day till I hit 12 hrs.

There are ways to increase light beyond 12 hours in bud safely and effectively too, after budset, but that is a whole nother thread…LOL

[MrWizard]

@shag

There are ways to increase light beyond 12 hours in bud safely and effectively too, after budset, but that is a whole nother thread…LOL

Please do, I would love to see this thread!

Cheers,
M

[Foreigner]

@shag

MH is very blue, with that you get very little stretch from blue light.
HPS is very red and you get lots of stretch from red light.

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.

[Hydro921]

I agree. I’ve grown many plants in the same conditions and it’s all about genetics

[TopShelfTrees1]

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

[TopShelfTrees1]

Always enjoy your threads and the info you share Shag

[shag]

@Foreigner

Does blue light inhibit stretch? Probably.

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.

@Foreigner

But it isn’t going to make a lanky plant significantly less lanky.

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

[shag]

@Foreigner

But it isn’t going to make a lanky plant significantly less lanky.

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

[Foreigner]

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.

[shag]

@Foreigner

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

[George]

@shag

MH is very blue, with that you get very little stretch from blue light

@shag

It is a situation where the plant thinks it is in the shade so it will bolt or stretch to get into the light.

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 …

[Foreigner]

I have grown a plant in full shade and it didn’t stretch. Barely grew at all in fact.

[George]

Bad genetics …