Darkness before harvest

[RosettaStoned]

So I forgot to turn my light off Monday night. I was going to harvest tonight but they will only have been in the dark for 12 hours. I should probably wait I'm assuming?

[Campesino]

I would give them at least 24 hours in the dark. 36-48 if you feel like waiting or if it better fits your schedule. From what I have read (a lot) and understood, 36-60 seems ideal.

[abadtrip]

Why can some 1 please point me to the science that says this works I want to read what u guys are reading I have found nothing on this in a scientific paper that has been through pair review and please if u have done it yourself and would like pair review send me your papers and I will run the experiments i am getting close to harvest so its a good time

[Waltermelon]

My next grow with clones I'm going to try this. It won't be peer reviewed, but it will be with clones that are going to be in the center of my tent, in the same conditions, same feed schedule, with before and after shots before harvest. It won't be peer reviewed besides a few folks on a fourm. But from what I've seen from some of the folks on fourms, scientific peer reviewed papers aren't as good as regurgitated dogma.
I got into a discussion a few days ago about ppfd and even though I posted just one of many study's done by ole Miss, that still wasn't as good as the "lighting sub-fourm helpers" word.

[Campesino]

abadtrip did you see the additional comments I left for you the last time we discussed this?

https://forum.growweedeasy.com/forum/growing-community/167116-dark-period-before-harvest

I would really love to see the "scientific papers done in labs" that you mentioned. As far as I can tell, there is no publicly available peer reviewed research that specifically tests this, so if you have scientific papers done in labs, please share them.
I am happy to answer your questions about the plant science part - but experimental data is not available.

[DingusKhan]

Waltermelon I'm with you. I'm going to try it on my next harvest too, split test. I will photograph, harvest some, put her in the dark for 36hours and photograph and cut some more.

[UrbZ]

It has to do with the long darkness period creating stress on the plant. Which in return floods them with goodies. Its a last ditch effort by the plant to finish and survive. Luckily its at the end of flower and will not affect sex/pollination.

[dontknownuttin]

This is good to know! I am working on my first photo it is far more work than autos!

[9fingerleafs]

the way i see it, the only pro i can reasonable believe from doing this is based on two very basic truths of cannabis. the first is trichomes are a protection from the light and only grow during the night. the second is trichomes are degraded (oxidized) and the THC turns into CBN (amber trichome) lowering the perceived potency, this process is accelerated by light and heat. so my reasoning is when you have a plant ready to harvest it means the trichomes are in its peak maturity, so leaving them in the dark and not watering will allow the plant to use the energy stored inside the plant to create more protection from the sun (lack of water i imagine also has to promote sun protection) but without the deteriorating effects of having high light and heat levels, therefore one could deduct the overall technique does give the plant another couple of days to work with what it already has and stop the trichomes from going bad. again this is my opinion and reasoning, ive done it in the past a few times and some other i didn't do it, i personally think it doesn't make much of a difference. i imagine it like this: imagine the day you harvest, now think two day before that, the whole benefit would be how much the trichomes "grew" in those two days plus the trichomes that would have otherwise went amber in those two days. i hope i didn't just ramble randomly and made some sense (:

[9fingerleafs]

campesino that’s some good info I dunno where I heard trichomes developed at night but I believe you thanks for clearing that

[Campesino]

9fingerleafs I bet I know where that thought comes from. Cannabinoids are powered by the Calvin cycle. The Calvin cycle is often known as the "Dark cycle". This is because early in the history of plant science they were able to determine that this cycle was happening during the dark. But it doesn't just happen during the dark, it happens all the time. The fact that it is called the "dark cycle" has led to a widespread belief that Cannabis plants need darkness to do certain things. I came across this misconception repeatedly in forums discussing Darkness (both dark periods during veg and dark periods prior to harvest). The only thing Cannabis needs darkness for is flipping its cycle to flower, and that is independent of photosynthesis and the Calvin cycle. As you correctly point out, the benefit of Darkness prior to harvest is that the plant doesn't need light to produce THC, at least for a while... The plant has enough stored sugars to power the Calvin cycle for at least 60 hours of darkness, during which time Cannabinoids are being produced and are not being burned off.

[Waltermelon]

The 60 hours of darkness thing sounds interesting to me. Maybe 7, 24 hour light and 50 hour dark cycles I think would be a worthy experiment.

[abadtrip]

Well I am just going to have to do it see for my self I grow autos under 24 hrs of light so I should see a huge difference at harvest after 36 hrs of darkness.

[Campesino]

abadtrip I understand your desire for peer reviewed studies, we would all like to see that data. If you are interested in an experiment and can set up four scenarios with Autos, this is how I'd set-up the "experiment"
Group 1 (control): Run these as you normally would (24 hours of light right up until harvest?)
Group 2: 24 hours light and then 48 hours darkness before harvest
Group 3: Gradually increase darkness over final two weeks. run light 12/12 or even 10/14 (on/off) for last 4-5 days, harvest at end of 12 or 14 hour dark period
Group 4: Same as group 3 with an extended darkness of 48 hours before harvest
My hypothesis is that group 4 would test the strongest and group 1 the weakest.

[RosettaStoned]

I am going to cut tonight since the troops are called in for it. We won't finish, so I can see if there is a difference from one day to the next. They'll be about 16 hours in the dark when I get to harvesting. Tomorrow will be 40 hours.

[DrPhoton]

"The Stichting Institute of Medical marijuana (SIMM), the first company to sell marijuana through the pharmacies of Holland, has been investigating the medical possibilities of cannabis, together with TNO laboratories and the University Leiden."

There has only been a small research effort into the subject of darkness before harvest, but it produced some interesting results. They found that seperating their crops and harvesting half after 72 hours of darkness, showed upwards of 30% increased THC in "some" strains. CBN and CBD were no different.

At night plants follow a cyclic function that operates differently compared to during the day. They accurately and mathemetically calculate how much photosynthate to burn for their duration of darkness. This calculation has been observed in plants and that they can accurately utilize photosynthate so that it is almost completely exhausted before light arrives. After which so a unanticipated duration of dark would send a plant into starvation mode.

The exact relationship of THC production is not completely understood, but it has been thought that it is used to protect itself from light. As such THC degrades with light and is continously being produced. So it might be plausable that darkness before harvest increases THC levels in plants, but i would anticipate based on current research that this effect would not be well benefitted past the standard 12 hours of darkness. As it has been shown plants degrade 95% of their stored resources by the time of their calculated night cycle is nearly finished.

I would personally still use 24hrs or more of darkness before harvest, as there are other properties that are of benefit.

[DrPhoton]

Happy learning

[DingusKhan]

Guys, that was quite a read. Thank you for the incredible lesson on light and plant physiology.

[Potted]

I have found this process to be a win/win no matter the reason.

[RosettaStoned]

Another question, since I have one ready and I am putting in the dark. Are there negative effects to the other two, which go into flush tonight, being in the dark longer?

[Campesino]

I'd add that you could go to 10/14 and harvest the one at the end of the 14, and then keep the others on 10/14 through the rest of Flush. That is most similar to how I plan to handle the same situation.

[RosettaStoned]

Ok thank Campesino, I'm not doing it tonight anyway. I have the lights off but will turn them on to the 10/14. It's just a touch past right now. They are all in the same net and can't be moved. The ones not ready will have week left as of tonight, so not too far off from the one that is ready.

[Locrian99]

I can’t be 100% but one of my gg’s that I put through a dark cycle about 60 hours had what I’m about 90% certain were bananas following the dark cycle that I did not see before. It was previously stressed during flower (mites/ph issues). I have not found any seeds in it either so far which makes me also think they showed up at the end. Not sure if those would form in the dark though.

[RosettaStoned]

To avoid this in the future I'll grow the same strain.

[KingKush]

Let's all grow the same strain! Whoever grows the dankest is the winner and gets to write the next article
I mean serious, sounds like a legit experiment. Let's all do what we can do with the same genetics and report back in 4 months

[RosettaStoned]

Will take some planning to get everyone who's in setup. There are so many variables to account for. I would be interested to see who's setup works best for what strain was chosen. If we found some serious players I have quite a few pineapple Express seeds from g13 labs. Would wanna trade of course, not just gonna give these ones away.

[oldjarhead100]

I haven't grown blueberry but here good things , I think White widow is a great strain , I also like the idea of all growing Nebula CBD even if its not her strain it would be a complement to her and this way we are all growing a strain we haven't grown before . that will certainly even the fields

[Campesino]

Yes, yes, yes, yes, and yes
Smoke fest!

[Potted]

A smokefest in August are u talking outside grow or in???

[KingKush]

Campesino RosettaStoned

Oh No! This means we have to agree upon some strains yikes!
This whole thread has been about darkness at harvest so this is something we must all strive to do- Leave some plants in the dark and let some finish with the lights.

I would even use whatever nutes but I will stick to soil for now. I feel if we grow the same strain with similar nutes and training, then we can judge mediums & environments against each other and have multiple witness testimonies about this "darkness before harvest"

Okay first thing to research friends is which strain or two would you like to try. I'll start with Nirvana seeds because Nebula is a fan and she doesn't steer us wrong.

Cheers!
K.K.

[Locrian99]

I might be interested as well my only concern is I’m going rafting aug 10-12 might be a little early to leave a seedling, I’ll probably be in though.

[Campesino]

Locrian99
I'd be happy to have you on board. I would like to propose an 8/15 ish start date so that would work. I will be busy the first week of Aug too.

[Locrian99]

This might be a good strain choice as well. Affordable etc. https://www.seedsman.com/en/c99-x-bl...eminised-seeds

[D.A.A.S.69]

I don't think your gonna see, that much of a difference, between them. The ones in the dark will look like they got more trichs, but there want be a big sudden giant explosion of trichs by keep in them in the dark either. At least thats my experience from over the years, of keeping them in the dark, but I will continue to keep them in the dark ,

[Campesino]

Yeah, but it'll still be fun to grow strains out at the same time. You in D.A.A.S.69 ?

[D.A.A.S.69]

No thanks, all I'm growing from now on inside, is autoflowers, but y'all have fun.lol