What Causes Stretch?

[GreatLife4All]

I found some surprising information the other day. I have been checking it out and can find nothing to refute these findings.

One of the common recommendations in hydroponics concerns the amount of ammoniacal nitrogen vs nitrates. It has always (to the best of my knowledge) been believed that lots of ammoniacal nitrogen was responsible for stretch (and that the use of nitrates helped to reduce it).

If you look at nutrient formulations - you can readily see this. If the formulation uses ammoniacal nitrogen - it is always restricted to 10% of total nitrogen. This was thought to be the right combination to allow growth and yet prevent stretch.

And then I came across this article: What Really Causes Stretch? | Greenhouse Product News

Interesting...

Let me summarize. They ran controlled tests checking to see if it was nitrogen or phosphorus that controlled the growth rate of the plants during stretch. It turns out - there is no correlation between Nitrogen levels and stretch - but a very high correlation between phosphorus levels and stretch.

So the claim being made is that to reduce stretch, we should restrict the phosphorus levels during this two week phase in the plant's life cycle. Once stretch is over, bump the phosphorus levels back to normal - and enjoy the rapid growth of buds on a smaller sized plant.

Anyone seen this article - or something similar?

Any comments on the findings?

Any one ever try this?

GL4A

PS - If you look closely at the nutrient schedule for Cyco, you will note that they use a massive infusion of Phophorus during week 3 of veg. I always wondered why they did this - I am assuming now that Cyco knows about this research and is using it to produce better growth right before flowering.

 

[JJ Bones]

Nice article, interesting information.

I've always thought we're using way too much phosphorous with these products, it's crazy.

 

[GreatLife4All]

Yes, I agree.

Theoretically we are producing bigger plants using all that phosphorus... which is pleasing to egos.

But if you are growing in a tent - stretch and big plants are your enemy. What if we could, instead, control growth so that the plant would reliably get 25% bigger during flowering? We could then know exactly how large to grow any one plant to fill the space that we have... no more tieing plants down late in flowering to avoid light burn...

 

[SWvoodoo]

Interesting. I assume you are referring to their XL product? This is recommended during week 3 of growth, Ive heard reports of it dropping the ph pretty badly, something about it being high in phosphoric acids??? I have just gone through a grow that had extremely little stretch and at the time was showing signs of what I now believe to be a slight P deficiency( dark green foliage , reddening of the stems and petioles), It wasn't until I started adding the PK boosters that it seemed to clear. I wonder if the two are connected.

 

[GreatLife4All]

Yes, I am referring to their XL product.

And yes, it is nothing but a very strong phosphoric acid. I initially assumed there were some hidden ingredients or something.

I have been trying to reduce nitrogen levels in order to avoid large plants from stretching. It would seem that I am completely wrong.

 

[SWvoodoo]

Most information ive read regarding intermodal stretch state day to night temperature differences and ec/moisture content of medium to be the leading contributors.
Basically stating that a night time temperature that is closer to daytime temps will cause less stretch exactly why is unclear to me but is supposedly tested and proven and the other factor, which makes more sense to me is the ec and moisture ratio of the medium. Basically stating that water molecules are needed to divide and expand cells and therefore the amount of water or more the availability of it will affect the plants ability to create new cells therefore limiting stretch. This can be done by limiting the amount of water you give your plants or the ec of the water that they are in/being given. obviously the higher the ec the less water a plant can take up due to the osmotic pressure being reduced.
Heres the interesting part... commercial tomatoe growers use extremely high ec (6.0) to limit the height of their plants in which they use a very high P ratio of nutrients as nitrates at such a high e.c. is toxic.
So should this XL product and its huge P ratio be used to raise the EC dramatically during that week of stretch to limit the stretch even????
My brain hurts.

 

[SWvoodoo]

I would be interested to see someone do a temp test supposedly if day and night temps are equal then stretch will be minimised. shouldn't be too hard to trial. I was also running very warm night temps on my latest grow so that also could have contributed to my minimal stretch.

 

[GreatLife4All]

Yes - I know about the environmental factors related to temperature. I can and have kept temps the same and varied them by as much as 15 degrees. That is where I am at right now in one of my tents... trying to maintain as large a gap between day and night as possible.

I posted this message about a week or so after I found the online article. I had some plants that were headed into transition and so I continued the 3-2-1 nutrient formula rather than switch to 0-2-4 or 2-2-2 - which would be normal. Both of these have restricted nitrogen and enhanced phosphorus. Consistent with current beliefs... as expressed in nutrient formulas.

Here is the issue though - I put up a new LED light for testing purposes... so that pretty much invalidates my comments as I am not able to say how much was the light... and how much was the switch from normal nutrient plan. And these are all clones - taken to an exact height - and I know how much they have stretched in the past.

One of the plants has barely increased in size - maybe 25%. This is one of the weird genetics that I found in some seeds... so let's not count that one. But last time it increased 50% in size during the stretch.

I have 2 OG clones - and they are much smaller than last time through. The one normal purple haze is also much smaller in size. These are both Sativa Dom - so they should have stretched mightily like the last two times in this tent. They both doubled in size last time during the transition (and continued to grow till the end - though at a much reduced pace).

The buds have started to grow quickly now during week 3 and all the plants are now starting to show P deficiency. So I am switching to 0-2-4 and flowering additives later tonight. The lower fan leaves are starting to look terrible - and it came on quickly... maybe two days ago. And I have to admit that I am having a hard time diagnosing problems under the LED... I had to turn it off and get a normal light in there. I am so used to HPS that I can see problems even with the yellow light.

I have never used an LED light before - so there may be something to the fact that the different light has helped to restrict stretch. I don't have enough information on this. The LED light is also 800W and I normally run a 400W HPS - though I have run as much as 600W... not much difference between the 400 and 600W for veg or transition from what I can see (which is why I was running the 400). A more powerful light - such as an 800W LED - could help to restrict stretch.... there could be a tipping point that I crossed.

Because I changed two things at once - I can't claim anything. But there is enough there that I am going to run 3-2-1 on the next set of plants during transition.... which went into the tent (the one with the ventilation failure) this weekend. I won't change anything this time except the nutes and will report back. These plants are Bay 11 and I know what they will do under a 1,000W HPS light. I will also shift to 0-2-4 with flowering additives after week 2. Learned my lesson on that one.

And I really don't want the plants to be as small as they are right now... I sorta overdid it. So I might even switch to 0-2-4 after a week and take some late stretch for the added size.

So I am thinking...

If you have small plants to flower... High P for transition to make up the difference.

If your plants get a little too big during veg... low P for transition to restrict stretch.

If you want higher bud density or have a small space (cabinet grows and small tents) - low P for transition.

If you want monster plants... veg for a long time and then hit them with high P in the transition.... Or low P to produce a monstrous bush.​

Wouldn't it be nice if we could control the plants like that? Or we might find that I have just delayed the stretch - we will see what happens when I hit them with a lot of P (relatively speaking) this week.

GL4A

 

[donpaul.p]

the only major different ive noticed is what veg schedule your going to 12-12 from,

gas lanter routine gives very little to no streat when you flip to 12-12, keep the plants under glr until they show sex then go 12-12, plants ready to flower without a stretch stage or if any its only slight.

going from 24-0 down to 12-12 creates more stretch due to the plant not being used to the dark period so it stretches to try and find the light,

so maybe a demenishing light schedule from a veg schedule to flower schedule would also help stop any stretch period,

cant help on the nutrients as my plants dont tend to stretch much anyway when i flip to 12-12, as long as the fully mature before going 12-12 then they can start flowering within a week of go 12-12, so now i only flip 12-12 when my plants have all shown me what sex they are then when i flip to 12-12 stretch is minimal, at least from my own experience with my set up thats what im getting happen,

i would use glr but ive been working on an auto strain so gone with 17-7 this last grow, autos grew well under that as well and got much bigger but took a couple of weeks longer to grow, but was worth the exra yield at the end.