An experiment to help determine the effect of different latitude on maturation time using a select cultivar

[Maria Sanchez]

And what do you suppose would happen if you grew this strain down near the equator? Having a critical photoperiod of 14.5 hrs, would it just start flowering in about six week regardless of when you planted it ?

Haha, that's a little trickier ...
I'm at about 25N, and care some experiences here.
My midsummer light is approx 13.5/10.5.
It seems most cultivars that aren't very heavy sativa/haze types will do the usual veg for maybe 4 to 6 weeks, then start to flower.

For ex., I ran/am running two Lemon 'n' Lime Jones, that is still mostly sativa but not extremely sativa. I put them out about March or April.
The breeder says they need about 10-12 weeks usually.
They both sexed after about a month, and one just immediately became a short bud-stick, the other one kind of flowered but slightly hesitated over June/July, and she's now a longer bud-stick that looks like she needs another 4-6 weeks, i.e., finish maybe late Sept to early Oct.

I'm also running a bunch of sativa / hazes, mostly some crosses of Neville's Haze, that are probably like 80%-95% sativa, started at the same time, with Thai, Kariba and other genetics in the mix.
Breeder says need from 12 to 16 weeks for these crosses.
They also showed sex after about a month or a little bit more, but by June they were just into full veg mode. There's a bit of variation between them, but most started flowering about early to mid August, aiming to finish in about Nov to Dec, at a guess (early days yet).

I've also run plants in this area that are photos and more regular hybrid of indica and sativa, and they also just veg for 4+ weeks to show sex, then just keep on flowering right through the middle of summer, like they don't care.

Running anything other than sativa dominant photoperiod plants here just gives a small plant, that ends up on a time frame something like an auto.
If I run them to veg over summer they get a bit bigger, otherwise they are really small.

Weird deja vu writing this post, haha!

 

[kendermag]

There are studies on other plant species, which detail a direct correlation between critical photoperiod and latitude, as well as between critical photoperiod and flowering time. I haven't found studies on cannabis, but I think it could be something similar to this:

 

[gorilla ganja]

@kendermag - I love the graph. How did you make it? Is there a site where you can punch in the data?

And what do you suppose would happen if you grew this strain down near the equator? Having a critical photoperiod of 14.5 hrs, would it just start flowering in about six week regardless of when you planted it ?

I think this is about right. Many people have complained about growing "Indica" or "indica" hybrids near the equator and getting small plants that don't grow much before flowering.

I think the plants also need a particular difference from the longest day. For example, at 35 N, the longest day is 14.5 hrs. But I don't think this specific cultivar would begin flowering at maturity there, but rather sometime in July as the days get shorter or, more correctly, as the nights get longer.
As we discussed, many things can also affect flowering onset. For example, these cultivars can be tricked into flowering a couple of weeks earlier by being root-bound in pots.

 

[kendermag]

I made the graph with Google Sheet.
Imported the data from this site:

https://www.pveducation.org/pvcdrom/properties-of-sunlight/calculation-of-solar-insolation

In the third graph, it's posible to adjust any latitude, then click on the graph for numerical data, select it, Copy and then Paste into a Google Sheet (Or Excel). Then make the Graph.
For multiple latitudes, copy/paste data from other latitudes.

If you're lazy, I can share the sheet from my drive.

 

[Old Uncle Ben]

Nice! A prediction that's what I'm talking about ! I was thinking like you but gorilla ganja makes the point that during the summer solstice they are much longer up north so they have further to go

You guys need to consider phytochrome development, cause that's what it's all about, at least with faves that are indigenous to areas where hormonal changes induce the flowering response. Say, 20* and north.

Equatorial varieties around 0 to 15 latitude seem to flower based on chronological age.

Phytochrome is a photoreceptor, a pigment that plants use to detect light. It is sensitive to light in the red and far-red light region of the visible spectrum. Many flowering plants use it to regulate the time of flowering based on the length of day and night.

Phytochrome manipulation for growing cannabis? | Grow Weed Easy

Learn about phytochrome manipulation to increase cannabis yields!

www.growweedeasy.com

Anyway, cool experiment. Good luck.

 

[Old Uncle Ben]

As we discussed, many things can also affect flowering onset. For example, these cultivars can be tricked into flowering a couple of weeks earlier by being root-bound in pots.

aka stress. Cold temps can induce stress and aid in the flowering response. Plant says "it's time to shit or get off the pot, winter is coming. Time to carry on the species".

 

[Old Piney]

Here's a picture of miss k today as you can see it's quite into flowering so as far as this experiment I believe it's a slam dunk. However I do think there might be a little more to the picture than a switch turned at a specific critical photoperiod , setting aside pot bound or cold temps. I'm up for another test next season maybe adding another latitude, like I tried with my buddy at 36 degrees north ( he killed gorilla ganja’s seeds ) and maybe another strain with a different critical photoperiod. I don't know just thinking out loud. I do believe that as long as the strain has a stable maturation time we don't need to be mailing clones around. I'll be honest @kendermag your chart is a wee bit over my head but I get the gist are you an engineer?

 

[kendermag]

kendermag your chart is a wee bit over my head but I get the gist are you an engineer?

Don't be overwhelmed by one of my graphs... I'm a chump, anyone here knows more than me about growing plants, which is what really matters.

I am dedicated to big data, making models that help predict events in the business world. I spend the day between graphs and reports, that's where my fucking habit of trying to represent things with graphs comes from.

I have grown the same clones as my friends, in different latitudes, from the Canary Islands to northern Spain.

The model based solely on the critical photoperiod is only an approximation, I believe it is the most important variable, but not the only one... as you have mentioned, there is the climate, the number of sunny and cloudy days, the cold, the space for the roots and the rest of those commented variables.

 

[Old Piney]

Don't be overwhelmed by one of my graphs... I'm a chump, anyone here knows more than me about growing plants, which is what really matters.

I am dedicated to big data, making models that help predict events in the business world. I spend the day between graphs and reports, that's where my fucking habit of trying to represent things with graphs comes from.

I have grown the same clones as my friends, in different latitudes, from the Canary Islands to northern Spain.

The model based solely on the critical photoperiod is only an approximation, I believe it is the most important variable, but not the only one... as you have mentioned, there is the climate, the number of sunny and cloudy days, the cold, the space for the roots and the rest of those commented variables.

I only ask about the engineer because my father was and my brother is an engineer and the both of them always solved problems with graphs and mathematically formulas. For instance even dropping a tree in a given space and that's what I do trees service as opposed to my brother tracking satellites. What is the difference in latitude between northern Spain and the Canary islands and did you document the differences in maturation of the clones? In addition to the variables mentioned I believe what @gorilla ganja was hinting at might well be true. A plant with a critical photoperiod higher than the longest day at that latitude, when planted out in the spring might not just flower in six weeks ,because it senses the days still lengthening

 

[Eltitoguay]

Between 43.5°N of the northern Galician coast (equivalent to the French southern border) and 27°N of the southern coast of the island of Hierro (equivalent to the original border between Morocco and Western Sahara).

 

[kendermag]

I only ask about the engineer because my father was and my brother is an engineer and the both of them always solved problems with graphs and mathematically formulas. For instance even dropping a tree in a given space and that's what I do trees service as opposed to my brother tracking satellites. What is the difference in latitude between northern Spain and the Canary islands and did you document the differences in maturation of the clones? In addition to the variables mentioned I believe what @gorilla ganja was hinting at might well be true. A plant with a critical photoperiod higher than the longest day at that latitude, when planted out in the spring might not just flower in six weeks ,because it senses the days still lengthening

In Tenerife (28ºN), a 14.2h CP clone begins to flower immediately outdoors, at any time of the year. In order not to become small, it was necessary to give it prior growth indoors.

In this case it seems not to matter that the days are increasing, the CP seems to prevail.

In the north of Spain (43ºN), this same clone was not advisable to take outside until mid-May.
If it was taken outside in April, it began to flower and then revegetated in May.

However, when planting from seed, it can be taken out in April, because you have an "extra month" while the plant is maturing, and it will not flower in April.


This same clone planted in southern Spain (37ºN) flowers 2-3 weeks earlier (mid-July) than in northern Spain (43ºN), that did it at the beginning of August.

​

In my experience with this clone and at these latitudes, the main factor was the CP, I'm not saying that what Gorilla Ganja says about increasing days is not true, just that I couldn't appreciate it.

Edit: The clone was a Critical Mass, and flowering at different latitudes lasted 55-65 days. I don't know if the differences were due to latitude, climate, or the tastes of the grower.

 

[Old Piney]

Nice! Another example confirming cp using a strain with a little lower cp at lower latitudes. So again it's looking like I'm wrong , the plant just flips a switch at a set photo period regardless of latitude. This is great and makes things very predictable. Once you've established the cp of a strain and the flowering time we can fairly accurately predict finish dates at different latitudes , setting aside pot bound or really extreme conditions. I suppose that you call the cp when you first notice flowers in the growing tips. Most seed co list flowering time ,some list finish dates but as we can see the finish dates vary according to latitude. It would be such an asset to the outdoor grower if the would list the cp as well.

 

[kendermag]

Nice! Another example confirming cp using a strain with a little lower cp at lower latitudes. So again it's looking like I'm wrong , the plant just flips a switch at a set photo period regardless of latitude. This is great and makes things very predictable. Once you've established the cp of a strain and the flowering time we can fairly accurately predict finish dates at different latitudes , setting aside pot bound or really extreme conditions. I suppose that you call the cp when you first notice flowers in the growing tips. Most seed co list flowering time ,some list finish dates but as we can see the finish dates vary according to latitude. It would be such an asset to the outdoor grower if the would list the cp as well.

I suppose that the real CP is somewhat higher, since when we see the first pistils, the plant had already entered the flowering phase, perhaps 1-2 weeks ago.

Then something interesting happens, and that is that in summer, there are more hours of daylight in higher latitudes compared to low latitudes, but these are concentrated in the vegetative phase.
Since they supposedly begin to flower when the CP arrives, from then on, in the flowering phase, they receive fewer hours of light than at lower latitudes, since the decrease in daylight hours is more aggressive.

Assuming that flowering lasts 60 days in both cases, the number of daylight hours is approximately 6% higher at 40ºN than at 55ºN during those 60 days.

Indoors, flowering is longer if it is done with a photoperiod of 14/10 compared to 12/12. I understand that the plant detects it and is in less hurry to finish flowering.
It is possible that in this case of outdoor, something similar will happen, and the flowering at 40ºN would be a little longer compared to 55ºN.... This 6% (over 60 days) would be 3-4 days.

It's also possible that I'm going overboard, I guess it's not as simple as using a calculator... In addition to the number of hours of light, I understand that the intensity of the days of intense sun is important... the DLI.

This thread is making me think about things I had never thought about...

 

[Maria Sanchez]

I would also think that Daily Light Integral DLI must factor in there somehow.
And temps, as low temps slow all kinds of metabolic activity, and light is needed for all activity, too.

 

[Old Piney]

I suppose that the real CP is somewhat higher, since when we see the first pistils, the plant had already entered the flowering phase, perhaps 1-2 weeks ago.

Then something interesting happens, and that is that in summer, there are more hours of daylight in higher latitudes compared to low latitudes, but these are concentrated in the vegetative phase.
Since they supposedly begin to flower when the CP arrives, from then on, in the flowering phase, they receive fewer hours of light than at lower latitudes, since the decrease in daylight hours is more aggressive.

Assuming that flowering lasts 60 days in both cases, the number of daylight hours is approximately 6% higher at 40ºN than at 55ºN during those 60 days.

View attachment 19052904​

Indoors, flowering is longer if it is done with a photoperiod of 14/10 compared to 12/12. I understand that the plant detects it and is in less hurry to finish flowering.
It is possible that in this case of outdoor, something similar will happen, and the flowering at 40ºN would be a little longer compared to 55ºN.... This 6% (over 60 days) would be 3-4 days.

It's also possible that I'm going overboard, I guess it's not as simple as using a calculator... In addition to the number of hours of light, I understand that the intensity of the days of intense sun is important... the DLI.

This thread is making me think about things I had never thought about...

Yes I have thought about this ,less light colder temps at higher latitude to finish flowering. Will this effect the flowering time., our experiment isn't over

 

[Old Piney]

I would also think that Daily Light Integral DLI must factor in there somehow.
And temps, as low temps slow all kinds of metabolic activity, and light is needed for all activity, too.

We shall see

 

[gorilla ganja]

As pointed out, the problem with this sort of experiment is determining exactly when flowering starts and ends—lots of room for opinion rather than fact.

This thread is making me think about things I had never thought about...

Here is the best video I have found on photoperiod and how it affects flowering. It's a long one at
2 hrs, but to anyone interested, it answers many questions.

 

[kendermag]

As pointed out, the problem with this sort of experiment is determining exactly when flowering starts and ends—lots of room for opinion rather than fact.



Here is the best video I have found on photoperiod and how it affects flowering. It's a long one at
2 hrs, but to anyone interested, it answers many questions.

Great video!!! I've seen it all.

I have made a Sheet in Google, anyone with a gmail account should be able to access it:

Sheet

If someone is interested, I recommend saving it on your drive (File>Make a copy) to be able to modify it freely, since several users can enter at the same time and create a conflict.

Selecting Year, Latitude, Critical Photoperiod and Flowering duration, it estimates the Beginning and ending of flowering.

Obviously this is just a rough estimate.

 

[Old Piney]

I suppose that the real CP is somewhat higher, since when we see the first pistils, the plant had already entered the flowering phase, perhaps 1-2 weeks ago.

Yes but that's all we can go by as far as I can figure. My guess ( so far they haven't been so good ) is that for our purposes this should be good enough for us to figure harvest dates fairly well and yes there has to be some standard of ripeness to call it finished

 

[ReprobateMind]

I don't have much to add to the discussion but the Friesland Indica from Kwik Seeds that I'm growing started showing flower formation on July 23, 2024 at 44º N. My Mendo Purps Bx1 #3 x Purple Urkle and Sweet 16 S1 from HumboldtCSI both started showing flowers on August 14, 2024.