# Growing with an 18 hour day/night cycle



## Hobbes (Jan 8, 2009)

Thoughts?

.

*Growing with an 18 hour Day/Night Cycle*

*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 acheived during an 18 hour cycle can be the equivalent to that acheived during a 24 hour cycle. So by running 18 hour cycles the same growth and yield can be acheived 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 accellerated 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.

.


----------



## exclamatio (Jan 8, 2009)

wow, this is really interesting, i have ordered my setup for my 1st grow and i will certainley try this method starting next week. Do you have any pictures of plants grown with this method?

Thanks for sharing the information mate


----------



## Doctor Cannabis (Jan 8, 2009)

This is incredible... if this works, this could be a major energy and time saver!

I'm excited to try this out in about 2 months, after this batch is all harvested.


----------



## SlowToker (Jan 8, 2009)

Do you think would work for any plant? Plants are plants, they veg they flower they die. This would save us lots of money on power is all crops worked this way.
Best of luck, I'm subscribed.

peace


----------



## Hobbes (Jan 8, 2009)

*"Do you think would work for any plant?"

*I can't see why it wouldn't for any 12/12 marijuana plant, like you said - plants are plants.*

.

*The idea is that you have an 18 hour light/dark cycle (6 light/12 dark) = one 18 hour day. So in 2 x 24 hour days you're plant grows 3 x 18 hour days. Most (all) of the trich and THC production are done at night, the day is just to gather energy. The plant absorbs most of the light from a 12 hour light period in the first 6 hours, so instead of inefficient light absorbtion (sp) for the last 6 hours of the light cycle the plant goes into it's 12 hour dark cycle.

7 x 24 hour days = 168 hours = 7 dark periods

9 x 18 hour days = 162 hours = 9 dark periods



Pretty cool

.


----------



## SlowToker (Jan 8, 2009)

Great concept, did you think this up?

Peace


----------



## Hobbes (Jan 8, 2009)

No, I was googleing for "reducing flowering time marijuana" and the article came up in another forum. 

The rotating 6 hours of light would be the deal breaker for me - I don't need the extra bud bad enough to plan my gardening around an 18 hour day.

.


----------



## BloodShot420 (Jan 8, 2009)

so does this actually work? any recorded grows using this schedule?

i use a PLC instead of timers so setting this up would be easy... I'm working with a strain i've done several times, i'll do it again and see if my results are the same (hopefully they wont all just go hermie)

I run 2KW so i could REALLY use that energy savings.... when i am in veg mode, my house goes over 4000 KWHrs per month


----------



## Hobbes (Jan 8, 2009)

I don't know if it would work ... it's an article, presumably from someone knowledgable, not the insane ramblings of a forum member. 

If the part about the plant absorbing most of it's energy in the first 6 of 12 light hours is correct then I think it could work.

.


----------



## SlowToker (Jan 8, 2009)

I'd say if it will work some hot shot somewher has written an article about it.
I'll see what I can find.

Peace


----------



## dat1kid (Jan 8, 2009)

hmm wonder how i could configure my timer to do this


----------



## BloodShot420 (Jan 8, 2009)

u will have to make 18h day timers...


----------



## Doctor Cannabis (Jan 8, 2009)

BloodShot420 said:


> u will have to make 18h day timers...


or change your timer settings every day... but i think that's not that hard since we all love spending time in our grow gardens...


----------



## BloodShot420 (Jan 8, 2009)

there is another timer called a cyclic timer that could work... 

or "harvest master" makes some expensive one...

changing them daily is not a good option - i had 6 timers that would need to be reset.... i like just peeking in on the weekends


----------



## SlowToker (Jan 8, 2009)

What does a PLC setup cost?


----------



## BloodShot420 (Jan 8, 2009)

they are modular, so as low as about 225, but with everything including co2 sensor about $650


----------



## murtymaker (Jan 8, 2009)

Is there any proof of this light schedule working?!? Wouldn't this be the standard of growing instead of the 18/6, 12/12 if the harvest was the same? I guess what I'm saying is if this worked why wouldn't everyone be doing it this way?


----------



## BloodShot420 (Jan 8, 2009)

yes, its still experimental... but maybe slightly past theory


----------



## nozthedon (Jan 8, 2009)

it wont the plants need 12 hours of uninterrupted darkness in order to initiate flowering. marijuana constantly produce a flowering hormone called phytochrome. Phytochrome initiates flowering,but if phytochrome is even exposed to a flash of light it is rendered inactive. to initiate flowering marijuana plants need a long and uninterrupted period of constant darkness each night for about two weeks.


----------



## BloodShot420 (Jan 8, 2009)

flowering is 6 on 12 off....


----------



## eza82 (Jan 8, 2009)

This will help!







Periods of Activity (Times during which Flowers are Open) in a Number of Intrinsic Flowering Plants (according to E. BÜNNING, 1953) 
http://www.biologie.uni-hamburg.de/b-online/e32/32h.htm

Reading this.......most flowering plants in this example only require a 6 hr OPENING period.... ranging from 6am - 8pm (except the night examples) but still need a 24 to 26hr total cycle period???

Why are the BIG dutch hydro farms on 12/12 ?
Conflicting for me.....
I thought a hormone called "florigen" controls budding and flowering. Long day plants require about 14 to 18 hours of light to produce just the right amount of florigen to flower and reproduce. Short day plants require about 10-13 hours of light. If short day plants are exposed to too many hours of light, florigen can be destroyed, preventing blooming..... too little it wont produce enough to max yield....

BUT IN THEORY I SUPPOSE a 6hr on 12 hr off could work ?? for bud
Maybey 10/12 or a 22hr day ?? for bud & trying to max hormone production.....


----------



## Doctor Cannabis (Jan 8, 2009)

eza82, thanks for great info... +rep


----------



## SlowToker (Jan 8, 2009)

Seems to me the 18 hour day, true or not would be very hard on a person as you would have to live your life around an 18 hour day. This if nothing else is a good reason to not try it.

If one could I'd say it would be worth trying just to see if you could trick mother nature!

Peace


----------



## Hobbes (Jan 9, 2009)

You're right about the 18 hour day, it's a deal breaker for a personal grower. Going into my garden during the routine of my day is relaxing, one of my moments of peace.

I too am curious why commercial growers don't use this, if it works. I'll search the web for reports of people growing on an 18 hour day.

While we could argue that plants evolved with a 24 hour day and therefore should be grown that way; we could also argue that mother nature often puts some extra capacity in her organism ... organisms ... organismes, so a flowering plant may only need 6 hours to gather the energy needed if the sun is overhead, no clouds, no shade. The extra 6 hours in the 12 in case it's a cloudy day, in the shade of a tree for hours a day, etc.

.


----------



## Hobbes (Jan 9, 2009)

*"Its proven, less light = less bud."*

Agreed. This is offset by adding CO2.

"_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 reason we grow with 18-6 (some 24-0) and 12-12 is because its what ACTUALLY IS PROVEN TO WORK. If there was a better way, thats the way it would be done"*

I think the system is too much work (scheduling) for most personal growers, and adding in CO2 comes behind a new electronic ballast or some other piece of equipment in the garden, though perhaps it shouldn't.

For Commercial growers most would presumably be using CO2 already, so they can't offset the loss in yield by supplementing with CO2. So they do extra grows, extra work, on an 18 hour day for no gain in yearly yield.

.


----------



## SlowToker (Jan 9, 2009)

Hey man, Google shows more hits on RIU regarding 18 hour grows than amy other site I can find. This should tell us something!

Peace


----------



## orgnlmrwiggles (Jan 9, 2009)

**everytime i say HID, i am refering to a metal halide**

sounds like a good concept i was thinking about something along the lines of changing times slightly to test different things. 

i honestly dont think this will work in shortening the flowering time tho. Im pretty if you did it this way, it might be a good experiment, i dont think it will shorten flowering time whatsoever though, if anything, maybe increase yield since your giving it light exactly how she can feed on it. 

My theory :

ok so if you think about from about march 20th til september 22, (in the northern hemisphere) days are longer by a small margine maybe a couple minutes. and this would be the ideal time to flower outdoors (outdoors = more yield) eventually if you add it up, doing indoor 12/12 is always the same, outside, flowering is more like, the month, May would be like 12.1hours of light/11.9 hours of dark. July would be12.2hours of light/11.8 hours of dark and august would right about 12.1hours of light/11.9 hours of dark such as may. so technically your lighting cycle is everychanging. also, the intensity of the sun in the first couple hours and last couple hours of the day would be less then what they would be during the day, by comparison(example on 4 plants), running 400watt HID 2 hours, then running a 400watt HPS for 4 hour and turning off the HID, then run the HID for 2 hours and turning off the HPS. then giving the plant 8 hours of darkness. 

maybe also, at the beginning of flowering, if using the HID>HPS>HID>Darkness theory, run hid for 2.1hours>hps 4.1 hours>hid 2.1 hours, darkness 11.7 hours. for the first 2 weeks, the next 4 weeks do, hid 2 hours>hps 4.5 hours>hid 2 hours/darkness 11.5 hours. and the final 2 weeks go back to run hid for 2.1hours>hps 4.1 hours>hid 2.1 hours, darkness 11.7 hours, or just 12/12 with hps and darkness.

also i believe kelvin somewhat changes throughout the year, (spring, summer, fall, winter) so i somewhat based the HID/HPS changes off that.



As a consequence, for half a year (from around March 20 to around September 22) the northern hemisphere tips toward the Sun, with the maximum around June 21, while for the other half year the southern hemisphere has this honour, with the maximum around December 21.


----------



## Jash1297 (Jan 9, 2009)

this would be cool to see a grow journal on


----------



## orgnlmrwiggles (Jan 9, 2009)

i would think working around an 18 hours day would be way easier. instead of 1 time a day, you have two seperate times a day in which you could go in to check your plants.


----------



## murtymaker (Jan 9, 2009)

Could I use this theory to make a 6on/18off cycle? It would help very much in my daily routine... any thoughts on that?


----------



## Mr.Funk (Jan 9, 2009)

Hey whats up? this would be my first time growing and i was wondering if the grow tents are pretty good? If i chose to get one what kind of lighting do you think i should use ? Thanks Peace


----------

