Flowering Cycle Triggers in Outdoor Growing

Penguin59 · Apr 3, 2012

Hi Everyone,

I've been growing for a while now indoors and outdoors and have a question about the flowering cycle with respect to the sun and daylight hours.

I know that flipping to 12/12 when growing indoors will force almost all strains to flower but I'm wondering at what point the flowering cycle begins outdoors. It must be at eleven hours and x amount of minutes but let me know what the science is behind it as I'd love to know.

I've been using the below link to find out the exact day length on any given calendar day and I want to use your inputs and this calculator to judge how much veg time I will get before the flowering period deadline. If that makes sense haha.

http://www.timeanddate.com/worldclock/astronomy.html?n=152

I'm in Australia too so we get quite long summer days by the way.

djonkoman · Apr 3, 2012

depends a lot on the srain, the strains that flower early enough to make it around here without too much mold will flower under 18/6. some people are able to keep them in veg indoor under 20/4, but even that can be problematic

the closer to the equitor the strain is adapted to, the shorter the daylength at flower

so in your case being a lot closer to the equator the trigger of your local utdoorstrains will probaby be closer to 12/12, but no saying how much it actually is

moondawg · Apr 3, 2012

Youve asked a question that rarely if ever gets much attention in our communty Penquin but its a very important question. In fact, its important enough to me that i spent several years researching and experimenting on the matter and now i know the answers. Let me give them to you now.

Many, most hybrid cannabis and specifically those strains with 30% indica or more, will begin to flower between 14.25 and 14.5 hrs of daylength. This fact is easily confirmed and i will give you the method. ITIS CRITICAL PENGUIN, to keep in mind that it takes 2 weeks from the time daylength triggers flower onset until you actually see pairs of white hairs begininng to form. IN the outdoors this means that when you first walk up and see flowers beginning to form on the plant, the daylength that actually triggered that flowering was 2 weeks ago. Use the tool ive provided below to determine what that daylength was at your lattitude.

http://astro.unl.edu/classaction/animations/coordsmotion/daylighthoursexplorer.html

The facts i present to you Penquin are easily confirmable with 2 differnt test:

Test 1: Place your indoor plants under 15hrs of lighting. Leave them for 2 weeks. You will observe that the plants DO NOT attempt to flower at that daylength. After 2 weeks, reduce the lighting to 14.25. EVERYTIME, the plants will begin to display flowering within 2 weeks. You can confirm your observations in reverse once you have seen the onset of flowering by once again, returning to the 15 hr lighting. The plants will over a few weeks return to veg cycle, or at the very least get stuck seemingly between flower and veg.

Since you are an outdoor grower, there is a second test for confirmation of the hrs that preciptate the onset of flowering. EX: At 38 N, the first flowers on hybrid strains are witnessed around August 1. This means that the daylength that actually triggered the flowering began 2 weeks sooner. If you use the tool i linked, you will see that the daylength at 38N on July 15 is just under 14.5.

The same holds true for your area. Consider your crops and plants over time: When do you generally start to see flowering? Make that determination and then check the link tool for you lattitude to determine what the daylength was 2 weeks before you normally see the flowering. I know for a fact that what you will find is that the daylength that was present when flowering was triggerd will be just shy of 14.5.

This flower trigger of 14.5 or so is why clones have to be planted after daylength reaches these levels to prevent spring flowering of clones.

Good luck to you buddy. Youre asking some good questions

Penguin59 · Apr 6, 2012

Thanks heaps for the speedy replies, djonkoman and moondawg!

moondawg, wow those are some amazing research conclusions you've outlined there. I definitely won't forget them. Good on you for going to the effort to find out.

Using your observations, once I decide how long I want to let my plants veg outdoors for, I can check the exact day when the daylight dips below 14.5 hours, and count back from that to know when to plant outside.

It was also an excellent point to note that, the evidence of flowering in cannabis plants only manifests itself after two weeks after being triggered. Certainly something to keep in mind.

All of the facts above will give me the assurances that all my timings will be correct and accurate in the upcoming outdoor season. Thanks also for the encouraging words my friend

Penguin

SeaMaiden · Apr 6, 2012

Moondawg has relayed what's closest to my experience, which dictates that ANY time you sufficiently reduce daylight photoperiod, flowering in cannabis is induced. I can take it from a 20/4 photoperiod and drop it to 18/6 and see generative phase growth begin, easily within two weeks.

In order to place plants outdoors, I use an interrupted photoperiod, which means that I'm interrupting the DARK phase of the photoperiod. I usually use two 2hr interruptions, and keep the daylight length matched to when I wish to put the plants outdoors.

Make sense?

Penguin59 · Apr 7, 2012

Hey SeaMaiden, thanks for stopping by!

I understand that you are trying to match up the outdoor day length with your indoor lighting regimen. I didn't quite follow why you interrupt the photoperiod for two hours at a time though. Would you be able to explain that a different way for me?

Penguin

SeaMaiden · Apr 7, 2012

Hmm... ok, let's say that I want to put out clones by April 30. According to my daylight calculator (a handy-dandy little slider kinda tool), at my latitude (34.4*N), my daylight length will be 13.4 hours.

So, 13.4 hours becomes my target daylight length. I set my timer so that the main daylight portion of the photoperiod is 13.4hrs, or slightly less.

Then, I interrupt the remaining dark portion of the photoperiod 2x, for 2hrs each time. Make sense?

A LOT of people advise to set daylight portion of the photoperiod to the longest day of the year, except that presents a bit of a problem--I want to put my plants out LONG before the summer solstice, months before that.

Here's the daylight explorer tool that I like to use: http://astro.unl.edu/classaction/animations/coordsmotion/daylighthoursexplorer.html

Penguin59 · Apr 9, 2012

Yep, I'm with you now mate. You've done this before clearly!

I'll keep in mind that tool you've linked when it comes time for the summer season down here in the southern hemisphere. Wish me luck.

Penguin

SeaMaiden · Apr 9, 2012

Oy, yeah, you're just about finished with your season, aren't you?

Yes, I've done this before, this year I won't be able to because I lost all my mother cuts after a knee reconstruction late last year. This year, nothin' but seed starts and since they haven't sexed, there's no need to worry about photoperiod as you have to with clones.

redclayguerilla · Jun 27, 2016

Moondawg,

So if I'm at 35 N and place my 4' tall plants out July 1st, or a couple of days later, will my plants flower and stay in flower mode and not revert back to veg? The daylight calculator I used online says I will have 14.5 hours of daylight until July 15th or so then daylight will be at 14.25 or so.

Currently they are on a 20/4 cycle (on at 5am and off at 1am). My logic, maybe ill-conceived, tells me that they will go into flower mode once I set them out and will continue to stay in flower mode long enough so that the daylight switch to 14.25 will help carry them through flower.

It'd be nice to put them out and harvest 2-3 weeks earlier instead of the typical Oct 5th-10th.

I'm in a hot zone for choppers and I would like to get them finished earlier rather than later.

Thank you all for your input!

chronosync · Jun 27, 2016

Same boat. I'm at 42N and my plants are outside now.

balsamfirgreen · Jul 2, 2016

Observed Frisian dew initiate flowering within 2 weeks of being placed outside from a 16/8 indoor regimen to 15:08/8:52 outdoor. They continued to produce normal, five-bladed leaves and strong vegetative growth (albeit with tons of pistils) for about 3 weeks, now just this week I'm starting to see three-bladed leaves, and now in the last few days single-bladed leaves (still serrated). I have no earthly clue what happened, clearly they did just barely start to flower and turned around. None of the other strains did this. only this frisian dew (dutch passion).

Any opinions on how this will affect yield?
Due to the fact that they went through a little "Stretch", so several tops required tying down horizontally.
Will they go back into flower as soon as it gets back down the day-length of may 22nd? (july 18th)... should noticably into flower by aug 1st, as was said once you see pistils its already switched about two weeks back.
Maybe it will make for easy trimming.
I've heard of indoor operations (dispensary-size grows) going 18/6 to 12/12 to 18/6 to 12/12 to finish. Any truth/logic to this? Why they would do this i have no idea but its essentially what has happened here on its own. Strange I say.

chronosync · Jul 2, 2016

Can't help you there as that's all over my head. My plants are still outside enjoying 15 hrs daylight, I can't tell if they are stretching or just growing like crazy, how they would have grown outdoors all along. They look happy as hell though.

BOMBAYCAT · Jul 2, 2016

Very helpful. I was wondering when I should take clones off an outdoor plant which may be special. I am at 40 degrees north. It looks like I should take clones the middle of July to get the 14 1/2 hours daylight before the plant thinks about flowering.

FoothillFarming · Jul 2, 2016

BOMBAYCAT said:
Very helpful. I was wondering when I should take clones off an outdoor plant which may be special. I am at 40 degrees north. It looks like I should take clones the middle of July to get the 14 1/2 hours daylight before the plant thinks about flowering.

You can take a clone from an outdoor plant up until around Mid July, or August at the latest. That is when the plant should still be in the vegetative state. You can still take clones through August, but then they reveg and take forever.

balsamfirgreen said:
Any opinions on how this will affect yield?

Maybe it will make for easy trimming.

It will effect yield to the point of a total loss. You will get thousands of popcorn nugs at best, that yeild zero unless made into concentrates. Some people say they pull out of it, but IME, once they throw single leaves, they never come back. If you do flower her out, trimming will be a nightmare. If you have a back up plant, replace her as soon as possible. Sorry, good luck. :tiphat:

Tynehead Tom · Jul 2, 2016

so if 30% indicas start flowering in that 14.25 hrs zone..... what about mostly sativas?
I'm at 52N and looks like august 17 is when I hit 14.5hrs. will probably have to light dep those starting july 15 to 21 until sept 25 when I hit 12/12 outside. they could finish naturally after that. Too cold here in October to grow weed without using energy to heat things at night.
this is a cool discussion, thanx for the info that's been posted, very handy indeed

chronosync · Jul 10, 2016

Wish I could help you guys more I'm just checking in to say, plants still outside no signs of flowering. I can't tell if they are stretching or just loving the weather, they look pretty good and are going into some big holes with some local super soil mixed with spent coco I'm gonna try!

stinky · Jul 11, 2016

moondawg said:
Youve asked a question that rarely if ever gets much attention in our communty Penquin but its a very important question. In fact, its important enough to me that i spent several years researching and experimenting on the matter and now i know the answers. Let me give them to you now.

Many, most hybrid cannabis and specifically those strains with 30% indica or more, will begin to flower between 14.25 and 14.5 hrs of daylength. This fact is easily confirmed and i will give you the method. ITIS CRITICAL PENGUIN, to keep in mind that it takes 2 weeks from the time daylength triggers flower onset until you actually see pairs of white hairs begininng to form. IN the outdoors this means that when you first walk up and see flowers beginning to form on the plant, the daylength that actually triggered that flowering was 2 weeks ago. Use the tool ive provided below to determine what that daylength was at your lattitude.

http://astro.unl.edu/classaction/animations/coordsmotion/daylighthoursexplorer.html

The facts i present to you Penquin are easily confirmable with 2 differnt test:

Test 1: Place your indoor plants under 15hrs of lighting. Leave them for 2 weeks. You will observe that the plants DO NOT attempt to flower at that daylength. After 2 weeks, reduce the lighting to 14.25. EVERYTIME, the plants will begin to display flowering within 2 weeks. You can confirm your observations in reverse once you have seen the onset of flowering by once again, returning to the 15 hr lighting. The plants will over a few weeks return to veg cycle, or at the very least get stuck seemingly between flower and veg.

Since you are an outdoor grower, there is a second test for confirmation of the hrs that preciptate the onset of flowering. EX: At 38 N, the first flowers on hybrid strains are witnessed around August 1. This means that the daylength that actually triggered the flowering began 2 weeks sooner. If you use the tool i linked, you will see that the daylength at 38N on July 15 is just under 14.5.

The same holds true for your area. Consider your crops and plants over time: When do you generally start to see flowering? Make that determination and then check the link tool for you lattitude to determine what the daylength was 2 weeks before you normally see the flowering. I know for a fact that what you will find is that the daylength that was present when flowering was triggerd will be just shy of 14.5.

This flower trigger of 14.5 or so is why clones have to be planted after daylength reaches these levels to prevent spring flowering of clones.

Good luck to you buddy. Youre asking some good questions

Hey there Moondawg,

This confirms what I have thought for years for my area but would like confirmation just the same. At a latitude of 32* daylight length today for July 11 is just about 14 hours. Actually it is 14 hours 9 min with each day getting a min shorter. The longest day summer solstice was June 20th with just 14 hours 18 min of daylight.

Now, does this mean that no matter when I put my plants outside they will start to flower soon after? Never having more than 14 hours 18 min of sunshine? If my memory serves me correctly every year I have tried to place plants out either too early or too late.

The table here:

http://astro.unl.edu/classaction/animations/coordsmotion/daylighthoursexplorer.html

would suggest San Diego just isn't sunny enough for any kind of outdoor massive vegetative growth without extra lighting. Haha never thought I would say that in all my years here. In my garden this year I grew my starts outside early on with just a back porch light keeping them from flowering. Seemed to work pretty well. I placed them out into the greenhouse without the back porch light the last week in May, First of June I believe.

According to the information in this thread my plants are starting to flower now... or the ones with more Indica in them at least right?

I always thought I was doing something wrong.... who know's I probably am. :biggrin:

Anyway if there are any other sunny San Diego growers that feel like commenting on when flowering commences in our beautiful city I would feel better about all the pistols I see in that there greenhouse.

Stinky

ExoticsRus · Jul 12, 2016

Right now I have 24 different strains growing this year in 100 gallon smart-pots
* I've topped them four times and was wondering if it's a horrible option to top the main part just one more time right before they go into flower ( if they haven't flowered, looks like they haven't). I don't want to fuck myself and I would prefer bushes obviously

* Would do you guys think?? , I looked around on a few boards for this question with a lot of non related and Bullshit related questioned.

redlaser · Jul 12, 2016

balsamfirgreen said:
I've heard of indoor operations (dispensary-size grows) going 18/6 to 12/12 to 18/6 to 12/12 to finish. Any truth/logic to this? Why they would do this i have no idea but its essentially what has happened here on its own. Strange I say.

That lighting change for flowering doesn't sound like it would help anything except delay flowering. But I've also never tried it.

I have heard of vegetative grows that were grown on 12/12 lighting, possibly even 10/14, with one or two extra hours of light interrupting the dark cycle. Reason for doing so is less electric bill. I would have to go look up who it is to be sure, but if I remember right it's guys from the Los Angeles area. Really clean setups, 3-500 lights a room it seems, up to ten foot plants in coco on tables. They have a name for it, green lighting or black or red lighting something like that. Saw it on ig.

I would agree that third week of July- first week of August is the start of flower generally. A couple years ago I took advantage of that by covering the plants until 9:30 p.m starting June 15 and they basically finished a month early. Had to keep them below a fence line

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