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

BACKCOUNTRY

Mourning the loss of my dog......
Veteran
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.

7710seasons2.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

Here is a thread with a list of US cities and their latitudes- List of longitude and latitude coordinates for North America

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.
 
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BACKCOUNTRY

Mourning the loss of my dog......
Veteran
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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BACKCOUNTRY

Mourning the loss of my dog......
Veteran
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 basicly, unless you live very near to the Equator, indoor finishing times will not be applicable outdoors.



I would like this thread to be a accurate resource for all members on this site, as such I welcome constructive criticism from members who believe(and have solid proof) that any part of this thread is inaccurate or otherwise flawed. Feel free to PM me or present your case in the thread civilly.
 
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hamstring

Well-known member
Veteran
Nice job BC

Not sure if it is worth while to mention or let you explain (you do a good job) that the amount of light a outdoor grower gets at his plot can be affected by natural plant/tree coverage.

Therefore some exact same strains will finish later even when in same latitude because of the different amount of light they may get at different grow plots.
 

Mr. Smoke

Active member
hamstring said:
Nice job BC

Not sure if it is worth while to mention or let you explain (you do a good job) that the amount of light a outdoor grower gets at his plot can be affected by natural plant/tree coverage.

Therefore some exact same strains will finish later even when in same latitude because of the different amount of light they may get at different grow plots.

I've had that happen to some clones before. In the same area but 1 spot got almost no morning light and they were budding 3 weeks earlier then the rest.
 

hamstring

Well-known member
Veteran
Mr. Smoke said:
I've had that happen to some clones before. In the same area but 1 spot got almost no morning light and they were budding 3 weeks earlier then the rest.

Right on Mr. smoke but I have had the other way around.

One plot gets all the sun available in the day and the other gets much less because of surrounding vegetation. The one with more sun finished earlier and of course better yields.
 

Jahkaya

Member
IT's very odd, I live at 29 lattitude, Hot and wet. I have a sativa that is in full flower and is no longer producing multiple blade leaves. I have hybrids that are in full Veg with but tiny preflowers.

In this world of only 14 hours of light Me thinks that some genes have been set into full flower so early.

So much diversity in Just one Genus.....I love it.
 

BACKCOUNTRY

Mourning the loss of my dog......
Veteran
Mr. Smoke & hamstring- I agree! Planting in shaded areas can result in slightly faster finishing times.
It has also been noted by many growers in the past that plants with more Eastern exposure, and lesser Western exposure also seem to finish a bit earlier, possibly for the same reasons as the tree shading.

Jahkaya- I have heard said before that many true tropical Sativas act like a "Day neutral" plants(Autoflowering), and may bloom according to Temperature, Rain cycles, or age, rather than by the cycles of the sun. At such a low lattitude, things other than Winter would be the reason the plants switch to bloom, since it is usually warm enough for most varieties year round.

And thank you much PrinceOfPersia, Sheriff Bart, Gunnarguchi, and teddybud!
 

DimeBag65

You will not be forgotten
Veteran
Great information to have on hand Backcountry! i have quickly skimmed through it but i am going to have to go back through and re read everything. Some vital information in understanding WHY your plant do what they do, when they do it :D

I agree on this should be a sticky, its some very valuable information for outdoor growers around the world. Keep the information coming and thanks alot for posting up, your contributions to this site, especially the outdoor forums is precious BC, thank you kindly for your time put in.

Always good to go over information again no matter what just to refresh the memory.
 

BACKCOUNTRY

Mourning the loss of my dog......
Veteran
Thanks everyone!

Thanks everyone!

Thanks DimeBag65!

After I compliled the Day length chart, a few questions came to mind for me:

1. How does the near lack of seasons(compared to higher Lats) affect growers at lower Lats? Like in Florida, S. Texas, Hawaii, and N. Austrailia? I imagine the conventional Indicas and Hybrids usually grown at higher Latitudes must be more difficult in these enviroments? As Jahkaya pointed out, it is possible even in a place where the day is never longer than 14-15 hours, but how do they fair?
Does anyone know of any Tropical auto-flowering varieties? Do they exist? Or are all Tropical varieties also Photo-sensitive(this would be pretty sensitive to feel that slight change in day length).

2. How long of a day can a non-Autoflowering plant be bred to bloom under? Could it be possible to breed a plant that would bloom and finish naturally in Eugene-OR(44.1N) before the end of August? Can Cannabis be bred to start blooming when the day is still longer than 15 or 16 hours?

3. I'm especially interested to hear from Canadian growers and growers in N. Europe who use many local and commercial early varieties. Some of these varieties seem to be Auto-flowering, some seem to be Photoperiod sensitive, and some I've heard can turn out as either in the same batch. Would any Northern growers care to talk about any of these exotic strains they have used and their observations about them?
 
M

mossy

Aw...BACKCOUNTRY..man.. :headbange
I am so pleased you started this thread.
I saw you having a constructive discussion about similar in another thread..but I had visitors and couldn't follow.

I have 3 kinds of girls.
Ones that go over with the season..
AF's..
and..what I call fast flowerers..
plants that aren't classed/named as AF..
but they ain't a kick in the arse off it.

They certainly do not seem to be photo-dependent..

Are these plants simply AF that haven't been named..or are they something else..

I have been studying up on the genetics in my grow..
and seeing these fast-finishers..against my true AF's genetics... :chin:
it has led me to make a few educated guesses as to the origins of the mystery cross in the Original LowRyder..
 
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BACKCOUNTRY

Mourning the loss of my dog......
Veteran
High there mossy!

I see in your grow thread that you live near 37*N, and you grow many beautiful plants. Feel free to describe your experiences concerning blooming and finishing times, it is especially interesting that you grow many different strains with distict methods and times of finishing.
 
M

mossy

Right..
I started with Original LowRyder #1
F1 Mazar x Original LowRyder
and LownRanger.
Bought seed.
Just incase anybody doesn't know..
Mazar is the indy side of Afghan.
The LownRanger was an Afghan x Original LowRyder.

The f1 LR crosses carried with them a 25% chance of AF on the LR side.

The first cross I made was Maz/Maz..the second was Maz/lownranger.
I have worked on these 2 crosses..and I am now just putting my first f4 hybrids out.
Both crosses are 50% LR genetics

My F1'S were grown full season..
My F2's were grown off season..in a cold..receeding natural light pattern
My F3's were grown off season..in a cold..increasing natural light pattern
All of my plants and crosses..up to F3..were 100% AF.

At F3..I got my split into AF's and NON-af's..but..that is where I expected it.
Everything comes out at F3.. :headbange
 
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