So, the summer solstice is June 21 and the fall equinox is Sept. 23…everywhere in the northern hemisphere. Days get shorter and shorter after June 21. I have read that the decreasing number of hours of daylight is what triggers flowering. Great. Is there a tipping point in hours of daylight that tells the plant to flower (such as the 12 hour day on the equinox)? [That does not seem right, or everyone’s plants would stay in veg mode until Sept. 23.] I want to try growing photos in the far north of the lower 48, where the growing season is short, but summer days are long. If I understood this better, it would help me choose the right variety I think.
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I’m in eastern 
And have them generally start to switch about the 14 hr day light mark.
Had a few start at 14 1/2 hrs last year but they were very mature plants. ( started 1 Feb )
Usually by the first week of August I’ll see preflowers starting on most.
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Excellent @Oldguy. I resisted responding with much of what you said as I have never grown outdoor so only know stuff in theory. No practical experience.
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@merlin44 Wish you folks were allowed outdoor brother. I know what you can do inside. 
Love to see what you could pull off with a nice outdoor lady. 
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I should try that sometime, just for kicks. I live in a “legal” state in the Pacific Northwest. I keep a very low profile nonetheless. I live in an area that is remote enough that I could grow a couple outside. Maybe I will start a couple indoor next March or April and move them outside when the nights are short enough. Could be some beastie plants.
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Absolutely. I started mine this year about the 4 th of April so should have some fairly good sized ones in the 30 gal pots. 
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Holy cow…you must need to use a hand truck to move them.
Do you leave them in the pots or transfer to in ground?
I am guessing that the deer would be attracted to them?
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They stay in the pots and in place once there.
No moving after the fact brother. .
My ground here is red clay and rock so pots it is.
6-8 ft tall is the norm and about the same across.
Keep lots of stakes handy.
Honestly they don’t seem to bother them. I have had moles and such uproot little ones but never any issues with anything over a foot or so.
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Same here. There is a thin layer of forest loam but just a few inches down…red clay and rocks.
Being on opposite coasts it is interesting that we have about the same soil.
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Interesting…I quess I will find out next summer.
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Just a point of note.
Usually by the time mine go out they’re already smelling pretty strong.
Not sure if that’s part of it or not but since I started putting them out a bit bigger , I don’t have deer issues.
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I will follow your lead on this. I have enough grow space to veg them for couple of months indoor and then another month or two outside before they would start flowering.
Edit: I might even take a couple clones rather than going from seed.
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Correct, provided plants are mature enough to flower anyways.
I’m not sure if there is an exact date or situation. I know it’s not the equinox because outdoor plants are well into flower here at that point, usually about 4-5 weeks in.
I think there is just a length of time it takes before daylight hours have reduced enough for plants to identify. Then another chunk of time for plants to transition and develop flowrer sites. Just like we see when growing indoors and move from 18 hours light to 12 hours light. The abrupt light change is there but it still takes time for plant to have flowers.
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Start now (late, is better than never).
Time to learn your yard outdoor grow needs, in prep for next year.
May take me a few years, But i will get there.
Legal is great, HIDDEN is best.
Watch out for yard beavers (rabbits).
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Thanks dbrn,
So my thinking now is that there are two simple requirements:
The plant has had ample time to vegetate;
AND
the summer solstice has passed / daylight hours are decreasing.
Maybe this is just stating the obvious? So, as long as the summer solstice has passed, it’s just wait for the plant to feel ready. (And hope you don’t have freezing weather.)
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Thanks dbrn!
| dbrn32 Moderator
May 18 |
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RustyJohnson:
decreasing number of hours of daylight is what triggers flowering
Correct, provided plants are mature enough to flower anyways.
Is there a tipping point in hours of daylight that tells the plant to flower (such as the 12 hour day on the equinox)?
I’m not sure if there is an exact date or situation. I know it’s not the equinox because outdoor plants are well into flower here at that point, usually about 4-5 weeks in.
I think there is just a length of time it takes before daylight hours have refuced enough for plants to identify. Then another chunk of time for plants to transition and develop flowrer sites. Just like we see when growing indoors and move from 18 hours light to 12 hours light. The abrupt light change is there but it still takes time for plant to have flowers.
never heard this before, but I see the resemblance.
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Mine starts about the first week of August, and I’m on the East Coast, You would think mabey there would be a different time because of our distance, That’s interesting 
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More accurately, when the night time period moves to 10 - 12 hours of darkness. In general, you have the idea.
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It’s based on hours of ‘sensed’ light and not all plants are created the same… For probably 99.9% of all photo-cannabis 15 hours of senses light a day will keep them in veg… From there shorter days will trigger certain varieties… Most are still safe at 14.5 hours, but a few random varieties might flip, as you get down to 14 hours the number that start to flip increases exponentially from 14 down, by 13 hours most will have flipped and by 12 hours 99.9% should have flipped… This is why indoor growers go to a 12-hour light to flip, it will essentially flip them all…
I use this site Sunrise and Sunset Calculator plug in your area, and it will tell you the number of hours of light a day… Note that if your plant has a very clear view of sunrise and sunset direction, it might sense give or take an extra 30 minutes a day of light, maybe a bit more… But, I would never gamble on that light being sensed…
Note that if you are growing outside in a Northern area, you will probably want to start your plants inside in March/April or similar and move them outside about June 1 when days hit 15 hours to be 100% safe and extend your growing season a bit, this also gives you time to pull clones… From that point when they flip will depend on the variety you have, I would start keeping a real close eye on them when daylight falls below 14, that should be August, keep notes on the number of daylight hours for what you are growing and you will have the start to your own calendar…
Also note, the plant doesn’t need much time to veg before it can flip, you can flip a plant quite early long before it’s grown enough to produce any significant amount of flowers…
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