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Finishing times, Photoperiod, Latitude, and how it all works!!

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  • Aug 16 2008 07:20 PM
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Posted 16 August 2008 - 07:20 PM

Here is a post I stole off another grow site from a grower named BACKCOUNTRY. I'm hoping that this will help calm the hysteria that seems to be spreading among GC nubes who are freaking the fuck out because they don't think their girls will finish. I didn't ask permission to use this because I can't post on that site for whatever reason. Anyway, thanks a bunch BACKCOUNTRY.

Quote:

Does 12/12 mean anything outdoors?
Often I have seen new members(or members mostly experienced in indoors) post threads asking when 12/12 occurs outdoors. Often they say they are looking for the time of the season when their plants will start blooming outdoors, many times they are trying to use this date(Sept 21 Equinox) plus the strains indoor finishing time to determine the outdoor finishing time.
But of course it doesn't work that way, we know that most strains have started blooming long before Sept 21st, but there is even more reason why indoor finishing times can't be applied outdoors.

One thing to realize is that as the day lights length shortens, the plants speed up their blooming, since most plants start blooming long before 12/12, outdoor plants will take longer to set into blooming and to finish than their indoor grown sisters would. So basically, unless you live very near to the Equator, indoor finishing times will not be applicable outdoors.
Finishing times, Photoperiod, Latitude, and how it all works!!
We all know the basics of vegging and blooming Cannabis..... when the day is long and the night is short the plant concentrates on vegging(growing), when the day length shortens enough, the plant starts to bloom.

But how does all this work?
Why does the same strain finish at different times in different parts of the world? Does 12/12 really mean anything outdoors? Why is Latitude(or "Lat") so important to some growers? What is a "Auto-flowering" plant?

Lets get into the meat of the subject shall we?..............

Photoperiod
The first thing to cover here is Photoperiod- Photoperiod is the ammount of time there is light in a 24 hour period. In Cannabis growing, Photoperiod is typically shown like this- 12/12 or 16/8, or 18/6, etc. The first number is usually the length of the lighted period, the second shows the balance of the 24 hours that is dark.
Outdoors the sun controls the Photoperiod. Its length changes through the seasons according to the movements of the sun in the sky, a matter of fact it causes the change in seasons. This brings us to......
Photoperiodism
Photoperiodism is the reaction of many flowering plants(including Cannabis) to changes in Photoperiod. Plants that experience Photoperiodism have pigment cells called Phytochrome that monitor the ammounts of light being absorbed by the plants(specificly the red end of the spectrum), and the length of day. Signals from the Phytochrome tell the plant to do many things, including to grow, bloom, and in the case of some trees, to loose their leaves and go dormant in Autum.

Most of these plants fall into three catergories concerning blooming times, that being- long day plants(blooms as day gets longer), short day plants(blooms as day gets shorter), and day neutral plants(blooming is not according to light cycles).
All Cannabis varieties are either "Short day", plants or "Auto-flowering" (known as "Day neutral" outside of the Cannabis community). So called "Auto-flowering" plants do not seem to take their blooming cues from the sun, and thus should be considered "Day neutral", as most seem to be geneticly programmed to bloom according to age insted.

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The Sun, Latitude, and why the same plants finish different times at different points on the globe

The year as we know it is basicly the time it takes for the Earth to make a complete loop around the sun. As the Earth makes this loop it shifts on its axis, so that either the northern half or southern half(Hemispheres) have the longer photoperiod.

file:///C:/Users/dave/AppData/Local/Temp/msohtmlclip1/01/clip_image001.gif

The shortest day of the year is called the Winter Solstice, this day occurs on December 21st in the northern half of the world, on the same day in the southern hemisphere they will have their Summer solstice, the longest day of the year. On June 21s it will be reversed, with the longest day of the year in the north(Summer solstice), and the shortest day in the south(Winter solstice).

Two days of the year are known as the equinoxes, one occurs March 21st and one on September 21st. These days represent the halfway point between the longest and shortest days of the year, on these days the day length is almost exactly 12/12 all over the world. If you are in the Northern hemisphere, Mar. 21 is the first day of Spring and September is the first day of Autum, reverse these dates in the southern hemisphere.

Latitude
Latitude is the east-west lines you see on a globe or map of the earth, they are spaced about every 111 Kilometers starting at 0 degrees at the Equator, and graduating north and south from there (every 111 KM) to the north pole(90 Degrees North) and South pole(90 Degrees south).

Here is a link to Wikpedia explaining Latitude-

Latitude

At the Equator the length of day doesn't change much from month to month, at both Solstices the length of day is about 12 hours, at both Equinoxes it is about 12 hours, almost perpetual 12/12.

Now lets take a look at Portland Oregon, this city sits near 45.4° N, which is about exactly halfway between the Equator(O°) and the North pole(90°N).
At the Winter solstice, the length of day is 8h 41m, at Summer solstice the day length is 15h 41m, and at the Equinoxes it is 12h 12m.

And now lets look at Anchorage Alaska, this city sits at 61.2° N, a little over 2/3 of the way to the North pole(90° N) from the Equator(0°).
At the Winter Solstice the day length is 5h 27m, at Summer solstice the day length is 19h 22m, and the Equinoxes are 12h 18m.

As you move away from the equator(either north or south), you see more distictness between the seasons and the length of days during those seasons.
Generally the closer you are to the Equator, the less difference there is between the length of day on the Solstices(the longest and shortest days of the year.
The further you are from the Equator, the more difference there is in length of day between the Solstices, making the Summer shorter and shorter, and the longest day of the year longer and longer the further you go from the eternal 12/12 of the Equator.

Here are the Latitudes for a few North American, European and Australian cities to show a example of the vast differences in latitude-

Darwin, Australia-12.4° S
Miami, Florida-25.8° N
Houston, Texas-29.7° N
Los Angeles, California-34.1° N
Atlanta, Georgia-33.9° N
Canberra, Australia-35.3° S
San Francisco, California-37.8° N
Reno, Nevada-39.5° N
Naples, Italy-40.8° N
Chicago, Illinois- 41.9° N
Boston, Massachusetts-42.4° N
Toronto, Ontario-43.6° N
Ottawa, Ontario-45.3° N
Seattle, Washington-47.6° N
Vienna, Austria-48.2° N
Vancouver, British Columbia-49.2° N
Calgary, Alberta-51.1° N
Warsaw, Poland-52.2° N
Amsterdam, Netherlands-52.3°
Edmonton, Alberta-53.3° N
Anchorage, Alaska-61.2° N

The Photoperiod sensitive strains of Cannabis are each geneticly programmed to start blooming when day shortens to a certain length*.
When these various strains are bred, they become acclimated to that latitudes photoperiod, they are bred to bloom and harvest before that areas climate becomes too cold and dark(or wet), usally to avoid major mold problems, or harsh freezing weather.
*Many experts agree that it is actually the length of the dark period that matters to plants.

When you take a plant that was bred in one location, and move it to a similar Latitude, say from 42° N to 43° N the plant should harvest at nearly the same time. But if you take a plant from 42° N to 50° N, its possible that the plant may not harvest early enough to beat Winter further up north.
__________________________
Here is a chart comparing the length of day for 4 areas, over the year. The first number is the length of day(meaning sunrise to sunset), the second number includes the twilight time before sunrise and after sunset(basicly the total length of visable light)-

----- Houston, TX 29.7°N--------Humbolt county, CA 40° N------Eugene, OR 44.1°N--------Vancouver,BC 49.2°N

Dec 21--10h 14m/11h 07m------------9h 22m/10h 23m--------------8h 52m/9h 58m--------------7h53m/9h 27m

Jan 21--10h 33m/11h 24m------------9h 51m/10h 49m--------------9h 26m/10h 30m------------8h 54m/10h 05m

Feb 21--11h 19m/12h 07m-----------10h 58m/11h 53m-------------10h 46m/11h 45m-----------10h 31m/11h 36m

Mar 21--12h 58m/12h 56m-----------12h 10m/13h 04m-------------12h 11m/13h 09m-----------12h 13m/13h 16m

Apr 21--13h 03m/13h 52m-----------13h 29m/14h 25m-------------13m 44m/14h 45m-----------14h 04m/15h 12m

May 21--13h 45m/14h 57m-----------14h 31m/15h 33m-------------14h 45m/16h 06m-----------15h 34m/16h 53m

Jun 21--14h 03m/14h 57m-----------15h 57m/16h 05m-------------15h 30m/16h 43m-----------16h 14m/17h 40m

Jul 06--13h 58m/14h 52m-----------15h 00m/16h 06m-------------15h 22m/16h 34m-----------16h 04m/17h 28m

Jul 21--13h 45m/14h 57m-----------14h 31m/15h 33m-------------14h 45m/16h 06m-----------15h 34m/16h 53m

Aug 06--13h 26m/14h 17m-----------14h 09m/15h 10m-------------14h 24m/15h 29m-----------14h 53m/16h 06m

Aug 21--13h 03m/13h 52m-----------13h 29m/14h 25m-------------13m 44m/14h 45m-----------14h 04m/15h 12m

Sep 06--12h 36m/13h 24m-----------12h 53m/13h 48m-------------12h 58m/13h 57m-----------13h 09m/14h 14m

Sep 21--12h 10m/12h 56m-----------12h 10m/13h 04m-------------12h 11m/13h 09m-----------12h 13m/13h 16m

Oct 06--11h 43m/12h 31m-----------11h 32m/12h 27m-------------11h 28m/12h 26m-----------11h 21m/12h 25m

Oct 21--11h 19m/12h 07m-----------10h 58m/11h 53m-------------10h 46m/11h 45m-----------10h 31m/11h 36m

Nov 06--10h 52m/11h 42m-----------10h 13m/11h 11m-------------10h 00m/11h 01m------------9h 35m/10h 43m

Nov 21--10h 33m/11h 24m------------9h 51m/10h 49m--------------9h 26m/10h 30m------------8h 54m/10h 05m

Dec 21--10h 14m/11h 07m------------9h 22m/10h 23m--------------8h 52m/9h 58m-------------7h 53m/9h 27m

Length of day Vs. Length of visable light
When you see people describe outdoor Photoperiod, they often use the "Length of day" to describe it. "Length of day" is defined legally as the time between sunrise and sunset, the problem with using this figure is that it doesn't count the visable light known as "Twilight", that occurs before sunrise, and after sunset, the day may actually be 1 hour(or more) longer!
Cannabis plants do have a cut off point where they no longer consider fading light as "day", I am sure this tolerence point is different for each strain grown. Obviously a full moon is not bright enough to affect Cannabis plants, but who really knows where cut off is?
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Replies (100)

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Posted 16 August 2008 - 08:38 PM

Thanks Dank. Beautiful find. Definitely a good and useful read. + rep for sure.

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Posted 24 June 2009 - 08:35 PM

so flowering usualy starts around 9-10 hours of darkness?

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Posted 25 June 2009 - 04:17 AM

Great info dankohzee, it answers a lot of questions I have been having on my grow this year. Explains clearly why (for us from the USA that order from overseas seedbanks) might end up with strains doing strange thing's here in California...I started with 11 in the ground on April 15th, lost 1, two showed male in the last two weeks, 7 confirmed females (some now appear to be going back to veg, but a couple look to be full flowering) and one still unknown but is a beautiful MJ plant in any case. Thanks for the post!

Edited by nevesone7, 25 June 2009 - 04:24 AM.


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Posted 25 June 2009 - 07:24 PM

so flowering usualy starts around 9-10 hours of darkness?


this post is about all the variables. strain, climate, location etc. there is no definite "flowering time" for anyone. o yeah and i nominate this for a sticky! anyone else?
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Posted 07 July 2009 - 02:03 AM

Man, great info. Thought I'd give it a little bump.

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Posted 07 July 2009 - 02:08 AM

Is it possible to make it a sticky ?

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Posted 07 July 2009 - 07:26 AM

I 2nd that, it's great info and should be right up there with all the other great info threads at the top. let's find out how we can make it a sticky and get it done.

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Posted 07 July 2009 - 08:25 AM

sticky sticky sticky!

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Posted 07 July 2009 - 03:20 PM

bump :)

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Posted 07 July 2009 - 03:23 PM

i agree, backcountry has some amazing grows on icmag.

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Posted 07 July 2009 - 05:28 PM

NICE ONE!!

Question, So after reading your post i would like to measure the current Photoperiod, you mentioned dusk, At what point do you consider it lights out? because this could be anywhere in between when i lose direct sunlight around 3 to when the sun goes down, to when it actually gets dark..

Your measurements seem to be pretty exact, Are you measuring by sunset?

Thanks and again awesome post! +rep and admins we need a sticky ichy on this post...


Btw im in Tampa area 27° 58' N 82° 32' W



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Posted 08 July 2009 - 07:23 PM

mods can we make this post sticky ?

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Posted 12 July 2009 - 02:58 AM

this post is about all the variables. strain, climate, location etc. there is no definite "flowering time" for anyone. o yeah and i nominate this for a sticky! anyone else?


yea ok, thx, i meant to say do indicas usualy start flowering around 9-10 hours of darkness or more?

im at 45 N, and it seems they're startin to show sex (blueberry 80% indica and mango 90%+ indica)

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Posted 12 July 2009 - 03:00 AM

yep this post's obviously worth a sticky!

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Posted 12 July 2009 - 10:24 AM

Thanks for keeping it bumped guys. Soon the main question in outdoor will be about when 12/12 is, lol. I doubt they'll make it a sticky though because it's borrowed. Maybe if someone would rewrite it in their own words...
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Posted 12 July 2009 - 10:28 AM

Thanks for keeping it bumped guys. Soon the main question in outdoor will be about when 12/12 is, lol. I doubt they'll make it a sticky though because it's borrowed. Maybe if someone would rewrite it in their own words...


Yep, that´s right.

When does 12/12 occur in my area?? will replace is it too late? as the favourite question of noobs who can´t be bothered to read the stickies.

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Posted 12 July 2009 - 10:30 AM

Haha! I haven't been in the outdoor section much since they put all the journals in their own section, but I bet there's a few there right now! Oh wait a minute...I'm in the outdoor section now!!

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Posted 16 July 2009 - 12:17 AM

Nice to see this moved to a sticky, it answered lot's of questions I had and I'm sure it will answer many more for others.

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Posted 31 July 2009 - 04:05 PM

NICE ONE!!

Question, So after reading your post i would like to measure the current Photoperiod, you mentioned dusk, At what point do you consider it lights out? because this could be anywhere in between when i lose direct sunlight around 3 to when the sun goes down, to when it actually gets dark..

Your measurements seem to be pretty exact, Are you measuring by sunset?

Thanks and again awesome post! +rep and admins we need a sticky ichy on this post...


Btw im in Tampa area 27° 58' N 82° 32' W


O Z covers that here:


Here is a chart comparing the length of day for 4 areas, over the year. The first number is the length of day(meaning sunrise to sunset), the second number includes the twilight time before sunrise and after sunset(basicly the total length of visable light)-

----- Houston, TX 29.7°N--------Humbolt county, CA 40° N------Eugene, OR 44.1°N--------Vancouver,BC 49.2°N

Dec 21--10h 14m/11h 07m------------9h 22m/10h 23m--------------8h 52m/9h 58m--------------7h53m/9h 27m

Jan 21--10h 33m/11h 24m------------9h 51m/10h 49m--------------9h 26m/10h 30m------------8h 54m/10h 05m

Feb 21--11h 19m/12h 07m-----------10h 58m/11h 53m-------------10h 46m/11h 45m-----------10h 31m/11h 36m

Mar 21--12h 58m/12h 56m-----------12h 10m/13h 04m-------------12h 11m/13h 09m-----------12h 13m/13h 16m

Apr 21--13h 03m/13h 52m-----------13h 29m/14h 25m-------------13m 44m/14h 45m-----------14h 04m/15h 12m

May 21--13h 45m/14h 57m-----------14h 31m/15h 33m-------------14h 45m/16h 06m-----------15h 34m/16h 53m

Jun 21--14h 03m/14h 57m-----------15h 57m/16h 05m-------------15h 30m/16h 43m-----------16h 14m/17h 40m

Jul 06--13h 58m/14h 52m-----------15h 00m/16h 06m-------------15h 22m/16h 34m-----------16h 04m/17h 28m

Jul 21--13h 45m/14h 57m-----------14h 31m/15h 33m-------------14h 45m/16h 06m-----------15h 34m/16h 53m

Aug 06--13h 26m/14h 17m-----------14h 09m/15h 10m-------------14h 24m/15h 29m-----------14h 53m/16h 06m

Aug 21--13h 03m/13h 52m-----------13h 29m/14h 25m-------------13m 44m/14h 45m-----------14h 04m/15h 12m

Sep 06--12h 36m/13h 24m-----------12h 53m/13h 48m-------------12h 58m/13h 57m-----------13h 09m/14h 14m

Sep 21--12h 10m/12h 56m-----------12h 10m/13h 04m-------------12h 11m/13h 09m-----------12h 13m/13h 16m

Oct 06--11h 43m/12h 31m-----------11h 32m/12h 27m-------------11h 28m/12h 26m-----------11h 21m/12h 25m

Oct 21--11h 19m/12h 07m-----------10h 58m/11h 53m-------------10h 46m/11h 45m-----------10h 31m/11h 36m

Nov 06--10h 52m/11h 42m-----------10h 13m/11h 11m-------------10h 00m/11h 01m------------9h 35m/10h 43m

Nov 21--10h 33m/11h 24m------------9h 51m/10h 49m--------------9h 26m/10h 30m------------8h 54m/10h 05m

Dec 21--10h 14m/11h 07m------------9h 22m/10h 23m--------------8h 52m/9h 58m-------------7h 53m/9h 27m

Length of day Vs. Length of visable light
When you see people describe outdoor Photoperiod, they often use the "Length of day" to describe it. "Length of day" is defined legally as the time between sunrise and sunset, the problem with using this figure is that it doesn't count the visable light known as "Twilight", that occurs before sunrise, and after sunset, the day may actually be 1 hour(or more) longer!
Cannabis plants do have a cut off point where they no longer consider fading light as "day", I am sure this tolerence point is different for each strain grown. Obviously a full moon is not bright enough to affect Cannabis plants, but who really knows where cut off is?
____________________________

Dawn is when you would begin counting daylight and Dusk is when you would stop counting. The twilight referred to is listed as civil twilight. It's basically about a half hour before Sunrise, Dawn, and a half hour after Sunset, Dusk. So just add an hour to the difference between sunrise and sunset to get your photoperiod, Daylight.

From now (since June 21) until Dec 21, the days are getting shorter and the nights are getting longer.

It starts getting dark around 3pm in Tampa? Houston is at 29.7N, so it shouldn't be much different from their time...except for the time zone difference. Quantity should be about the same. It's not "Dark" in Houston until a little before 9pm. Are you behind a high-rise?

You can Google "When is my civil twilight?" or "Civil Twilight calculator" for your specific times.

Edited by TexasToaster, 31 July 2009 - 04:09 PM.
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