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Old 12-14-2018, 07:04 AM
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Default Controlling sativa stretch using low light

The sativas I'm finishing up stretched for 6 weeks and my tent was a jungle. I need to do a better job controlling stretch on my next sativa grow. I flower rooted clones in 4-gallon hempy buckets and I know that using smaller hempy buckets is one potential solution. But I noticed that one plant in my current grow had much less stretch than the others, despite the fact that the seed plant it came from stretched just as much as its seed plant siblings. The difference is that plant was a flowered a couple weeks after the others, and by the time it made it into the flower tent, it was light deprived under the canopy created by its sisters.

I did a little reading on stretch and the "common knowledge" is that high light intensity controls stretch. Well, on the contrary, I have a manageable-sized sativa in my tent whose height was definitely controlled by being starved for light when it was first flowered. It has a much smaller root mass and doesn't drink much, so the yield will suck, but it's definitely manageable. So I'd use less than full light, but more light than that plant got. So I'm thinking I might run my lights at half power for the first 2-3 weeks of flowering to try to control stretch.

Thoughts?

Last edited by Marcus_in_the_Darkus; 12-14-2018 at 07:07 AM.
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Old 12-14-2018, 08:30 AM
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Low light is limiting the energy going into the plant. You said it yourself, the yield will suck. Vegging at 12/12 with the light on for an hour or so in the middle of the dark period works well to control stretch in sat doms.
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Old 12-14-2018, 12:32 PM
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What lights are you using i.e. spectrum? 2k, 4k, or 6k?


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Old 12-14-2018, 08:28 PM
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In my experience growing, it is not too much light that creates stretch, its too much HEAT. Keep them under 80 deg. F. to reduce stretch. I grow outdoors mostly and the more sun, the less they need to stretch. The sun produces way more light than you are typically going to get indoors with a broader spectrum. Not enough light will also create stretch, especially in seedlings.
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Last edited by Big Sur; 12-14-2018 at 08:39 PM.
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Old 12-15-2018, 02:37 AM
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Let the tops of the plant grow above the light into a shaded area above the reflector of whatever sort you have.
They stone cold shut down stretch when you do this.
The plant doesn't want to be in the shade.......use that to your advantage.
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Old 12-15-2018, 02:51 AM
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Quote:
Originally Posted by Big Sur View Post
In my experience growing, it is not too much light that creates stretch, its too much HEAT. Keep them under 80 deg. F. to reduce stretch. I grow outdoors mostly and the more sun, the less they need to stretch. The sun produces way more light than you are typically going to get indoors with a broader spectrum. Not enough light will also create stretch, especially in seedlings.
G `day MID

Less light = less vigour .
To help structure .

More blue and no shading .
Red spectrum causes stretch . MH or TL 5 for veg .

Lolipop so the plants don`t sense infra red on the lower leaves .
Top several times .

Still gonna stretch during flower though .

Thanks for sharin

EB .
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Old 12-15-2018, 12:54 PM
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Yep, all of the above. I use 6k bulbs, trim the bottoms, keep the plants off to the side, min. nutrient, higher humidity, temps in the 70's, trellis them, and leave em alone. Still plan on 3x stretch during flower.

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Old 12-15-2018, 09:01 PM
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Quote:
Originally Posted by Marcus_in_the_Darkus View Post
So I'm thinking I might run my lights at half power for the first 2-3 weeks of flowering to try to control stretch.

Thoughts?
I can only add one thing to the convo. I read some of the gw pharma trials on growing glasshouse plants in the UK. I think this stood out as one of the most important points to growers...

It suggests that "the irradiance conditions on the very beginning of flowering have the greatest potential impact on the final yield." It also seems to not just affect yield but potency as well.

Pages 120-126

https://archive.org/details/CANNABIS...UTICAL/page/n1
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Old 12-16-2018, 05:48 PM
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I appreciate the feedback, compadres. Herewith some responses to the points made so far...

Quote:
Originally Posted by beauthebulldog View Post
Low light is limiting the energy going into the plant. You said it yourself, the yield will suck. Vegging at 12/12 with the light on for an hour or so in the middle of the dark period works well to control stretch in sat doms.
Thanks, BTB. I've read about the energy savings of vegging short-day plants in by flashing the lights midway through the dark period, but didn't know it could control stretch. I think that's moot in my situation though because I flower rooted clones without any veg time and they still stretch out of control. Also, the idea behind using low light is to intentionally limit the energy the plant receives to control root mass and, thereby, stretch.

Quote:
Originally Posted by musashi View Post
What lights are you using i.e. spectrum? 2k, 4k, or 6k?

I use 6k bulbs, trim the bottoms, keep the plants off to the side, min. nutrient, higher humidity, temps in the 70's, trellis them, and leave em alone. Still plan on 3x stretch during flower.
Great advice, brother Musashi. I use LED COBS, half are 3000 K and the other half are 3500 K. Next set of lights I build will probably use 5000 K COBs, but probably not for this next grow. I didn't trim bottoms last time and I will going forward. A 3X stretch would be acceptable, but I think my last batch of sativas stretched something like 8X.


Quote:
Originally Posted by Big Sur View Post
In my experience growing, it is not too much light that creates stretch, its too much HEAT. Keep them under 80 deg. F. to reduce stretch. I grow outdoors mostly and the more sun, the less they need to stretch. The sun produces way more light than you are typically going to get indoors with a broader spectrum. Not enough light will also create stretch, especially in seedlings.
Hey, Big Sur! Keeping the heat down is NOT a problem in New England until June or July, so heat isn't an issue. But the limited stretch of the light-starved plant I'm currently growing proves that not enough light can actually control stretch.


Quote:
Originally Posted by n2ishun View Post
Let the tops of the plant grow above the light into a shaded area above the reflector of whatever sort you have.
They stone cold shut down stretch when you do this.
The plant doesn't want to be in the shade.......use that to your advantage.
That's good information. So I could set my lights a little below the intended top of my canopy, let the apical flowers grow through and above the fixture, and then presumably raise the lights after the stretch is over. That sounds like a doable plan.

Quote:
Originally Posted by Elmer Bud View Post
Less light = less vigour .
To help structure .

More blue and no shading .
Red spectrum causes stretch . MH or TL 5 for veg .

Lolipop so the plants don`t sense infra red on the lower leaves .
Top several times .

Still gonna stretch during flower though .
Hey EB. I was thinking less light, less vigor during root development, essentially giving the same result as using smaller pots. I don't really like to lollipop because I want to observe the structure of the natural plant as much as I can while pheno hunting. The thing that appeals to me about light deprivation is it can "bonsai" the plant to an extent, so that it can be flowered without training to observe the natural branching and bud structure.


Quote:
Originally Posted by CannaFish View Post
I can only add one thing to the convo. I read some of the gw pharma trials on growing glasshouse plants in the UK. I think this stood out as one of the most important points to growers...

It suggests that "the irradiance conditions on the very beginning of flowering have the greatest potential impact on the final yield." It also seems to not just affect yield but potency as well.

Pages 120-126

https://archive.org/details/CANNABIS...UTICAL/page/n1
Wow, Fish, thanks for bringing the tech! I need to read that article in full and better understand how they set up the study, but I think this is the money shot:



I missed the part about lower potency potential from lower light levels during the stretch. Where was that suggested?

My interpretation is that root mass develops rapidly at the onset of flowering, especially in sativas, where the stretch and root mass growth go hand in hand. Therefore less light = less root mass = smaller plant = lower yields. So my idea is to reduce light over some portion of the first 6 weeks of flowering to control the root mass and the ultimate size of the plant.

Based on all the good information that you have shared, the measures I could take to better control stretch in my situation, include:
  • Use smaller pots. My 4-gallon pots simply hold too much root mass and plants that grow too big for my 4x4 tent setup. I'm thinking of these 3.5 gallon square pots, which would make fine hempy buckets. Only a little smaller than my current 4-gal setup, but it would help. Plus I'd pick up a couple inches of grow height.
  • Use 5000 K lights. I might build these and sell my current setup.
  • Lower lights to ~6" below ideal canopy height at the flip, let the apical buds grow above the lights and reset lights to final height after ~6 weeks.
  • Lower light intensity during a portion of early flowering. Maybe 50% power for the first two weeks then ramp it up each week to 100% power at week 6.
  • Reduce feedings.
  • Trim bottom of plant.

I'm not sure what combination of the above I'll try, but I am still considering light deprivation during early flower. I don't care if I lose a little yield, but I don't want to lose potency. Ideally I want to control the size of these plants without training to ~1.2 m tall to the tip of the apical buds. I'll post up a pic later of my prototype light deprived punto roko x mangobiche. She's a beauty, and she's the perfect size for an indoor sativa pheno hunt.

Last edited by Marcus_in_the_Darkus; 12-16-2018 at 05:55 PM.
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  #10  
Old 12-16-2018, 08:44 PM
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Hey Don Marco, I may have made up that extra part about potency, but I'm pretty sure I read something implying that. I'll scan back over it when I get a chance. It's a cool read. There's some fun info about CBD/THC ratios and temperature. Also a good comparison of light cycles btwn 11/13, 12/12 and 13/11.
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Last edited by CannaFish; 12-16-2018 at 08:54 PM.
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