# Growing with an 18 hour Day/Night Cycle!



## DND (May 24, 2008)

I came across this article a few days ago and thought this is interesting. The theory makes sense to me, but I'm not sure how this would work with cannabis. I will be trying this in a couple of months, but in the mean time ... anyone starting a new grow that is willing to try this? Or has anyone tried it before?


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## DND (May 24, 2008)

*The Theory*
*The theory behind the 18 hour Day/Night cycle is that during a normal 24 hour light cycle plants will usually achieve high growth rates peaking at 100% capacity during the first 50 - 60% of the day. The growth rates will then diminish rapidly and the last 20 - 30% of the day achieves minimal growth. So by reducing the length of the day we are triggering an increased growth mode where the growth rates are at their peak for the majority of the day. This effectively achieves a very fast growth cycle with full yield potential. 

NOTE: To achieve these incredible growth rates it is important to provide maximum light intensities and CO2 enriched conditions. The recommended lighting is 600W per square metre.*​ *The Cycles*
*Vegetative Cycle - * *Lights ON 14 hours* *Lights OFF 4 hours* *Flowering Cycle - * *Lights ON 6 hours* *Lights OFF 12 hours* *The Benefits*
*The growth achieved during an 18 hour cycle can be the equivalent to that achieved during a 24 hour cycle. So by running 18 hour cycles the same growth and yield can be achieved in 75% of the time.*
*Reduced day lengths also mean reduced power consumption. Grow more and use less power. Who can argue with that?*
*For example, an average crop grown from seed using a 24 hour day/night cycle will have a 4 weeks grow cycle and an 8 weeks flower cycle. This equates to 28 days @ 18 hours a day and 56 days @ 12 hours a day = 1176 hours of light over 12 weeks.

An accelerated crop using an 18 hour day/night cycle will achieve the same yields using a 3 week grow cycle and a 6 week flower cycle. This equates to 21 days @ 14 hours a day and 42 days @ 6 hours a day = 546 hours of light over 9 weeks resulting in a 40% reduction in power consumption and a 25% reduction in crop time.*



Source: Intelli-Cycle Digital Cycle Timer

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## ganjagoddess (May 24, 2008)

sounds lovely but I highly doubt that only 6 hours in flowering mode of light is benificial to the plant whats so ever.

THere is another cycle outthere called planet X light cycle.

Its something like 21.5 hour days, where the plant get 14 some hours of light and the rst dark... It was developed by some scientist specifically in relation to cannabis....

I dont know, just stick to 24 veg and 12/12 flower...

wouldnt more light in flower be better always.

Also really messing with light cycles can cause hermies, so I just play it safe.


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## JiggyJogger (May 25, 2008)

sounds cool ive been thinking about what if u did a variation on 12/12 and run 6/4
so its kind of like 2 days in 1. its just an idea tho i have no idea if it would work..do any of the rollitup botonist know if a plant would flower on 6/4 light cycle?


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## HippieMan (May 25, 2008)

what if you were to like


would that work?


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## DND (May 25, 2008)

I'm going to do a side by side comparison using the following...

18/6 veg ---- 12/12 flower

14/4 veg ---- 6/12 flower 

Stay tuned...


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## panhead (May 25, 2008)

Sounds silly to me,the information quoted is a sales pitch written by the company selling the intelligent timer,of course they'll make it sound all technical & give a bunch of reasons that sound plausible,it sounds like snake oil to me.

If this method was grounded in even the slightest bit of fact based information there would be atleast 1 peer reviewed white paper on the subject,ive looked & there is no information on the net other than sales pitches & speculation.

If it were me i'd stick with tried & true methods.


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## DND (May 25, 2008)

panhead said:


> Sounds silly to me,the information quoted is a sales pitch written by the company selling the intelligent timer,of course they'll make it sound all technical & give a bunch of reasons that sound plausible,it sounds like snake oil to me.
> 
> If this method was grounded in even the slightest bit of fact based information there would be atleast 1 peer reviewed white paper on the subject,ive looked & there is no information on the net other than sales pitches & speculation.
> 
> If it were me i'd stick with tried & true methods.


I hear ya, but I'm going to try it and see for myself.


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## WormSlayer (May 27, 2008)

DND said:


> I'm going to do a side by side comparison using the following...
> 
> 18/6 veg ---- 12/12 flower
> 
> ...


Good man! I hear these odd time schedules talked about often, but have yet to see an actual comparison grow.


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## The Stig (May 30, 2008)

sounds interesting... keep us updated


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## amywagner (Jul 9, 2008)

how did your crops do on that new lighting system you mentioned?


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## techhead420 (Jul 11, 2008)

panhead said:


> Sounds silly to me,the information quoted is a sales pitch written by the company selling the intelligent timer,of course they'll make it sound all technical & give a bunch of reasons that sound plausible,it sounds like snake oil to me.
> 
> If this method was grounded in even the slightest bit of fact based information there would be atleast 1 peer reviewed white paper on the subject,ive looked & there is no information on the net other than sales pitches & speculation.
> 
> If it were me i'd stick with tried & true methods.


Listen to this answer people. This is nothing but a sales pitch and if there is no independent research to back the claim then that is a sure sign that the claim is BS.


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## kyoinidaho (Jun 21, 2009)

hey dnd, did you ever try that with an 18 hour cycle? definately curious...


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## normancay (Jul 3, 2009)

I am using this method ..


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## China (Jul 3, 2009)

Start a grow journal and post a link. I'd watch it.


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## Hairy Bob (Jul 3, 2009)

DND said:


> *An accelerated crop using an 18 hour day/night cycle will achieve the same yields using a 3 week grow cycle and a 6 week flower cycle. This equates to 21 days @ 14 hours a day and 42 days @ 6 hours a day = 546 hours of light over 9 weeks resulting in a 40% reduction in power consumption and a 25% reduction in crop time.*


Unfortunately this doesn't quite add up. Say you start this on a Monday at 00:00. So on Monday they get 14hrs light, then 4 dark, then another 6 of light before 00:00 on Tuesday. Then they get 8hrs light, 4 dark, and another 12 of light by midnight. Wednesday they get 2hrs light, 4 dark, 14 of light and another 4 of dark, then the cycle repeats itself every three days. this gives an average of 18hrs 40mins of light per day over each 3 day cycle, so you are actually using slightly more energy running the lights on this cycle than if you used 18/6.
Flowering, then. Again, we'll start on Monday, 00:00. 6hrs light, 12 dark, 6 more light. Tuesday starts with 12 hrs dark, 6 light, and 6 dark, Wednesday has 6 dark, 6 light and then 12 dark. Average of 8hrs of light per day.
This means that for the 3 week grow cycle, the light will be on for 396 hours, then a further 336 during bloom, for a grand total of 732 hours over a 9 week period.
I'll grant that if the rest of the theory is sound, the time saved would still save money, *if *the yield was not reduced by giving them less light. They say that for the second half of the day, the plant is growing at 20-30% of it's potential, but it is still growing. Therefore if those hours of the day are not present, you are bound to lose yield. Which one of the methods would give better results on a cost/gram basis could only be determined by experimentation. I certainly wouldn't put my faith in the theorisations of someone who would overlook such a basic point in their calculations, much less if they were trying to sell me something related to the point they were trying to make.


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## normancay (Jul 12, 2009)

China said:


> Start a grow journal and post a link. I'd watch it.


I just started one actually...link in signature...


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## GangstaChronic (Jul 12, 2009)

thanks normankay for posting the link.

how did the originator of this post do?


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