Lights off 24 hours before harvest - then back on again?

0james0 · Feb 14, 2016

I've read plenty on the lights off for 24-72 hours before harvest. I've nearly always done it and I do believe it brings out the event in them.

Got a new theory, given that the THC and resin is produced in part to act as sunscreen. The darkness stresses the plant to make it more of it, but maybe after a period of darkness, a period of all light will make the plant produce even more to try and protect itself from the unexpected sun?

I'm now at the period of 24 hours darkness done and wondering if before I waste my time trying this, if anyone has before?

qwizoking · Feb 14, 2016

Resinhound · Feb 14, 2016

This ranks right up there with pushing tacs into your stem,basically bullshit.But youll always hear some anecdotal account that this and other things work.

Bottom line dude,its your plant.And you will never know if it worked anyways..so I say, if it inconveniences YOU,then dont bother.Otherwise,go for it.

qwizoking · Feb 14, 2016

0james0 said:
Got a new theory, given that the THC and resin is produced in part to act as sunscreen. The darkness stresses the plant to make it more of it,

"Stressing" the plant doesnt belong in the advanced section. And is inaccurate or ignorant.. what are these stressors and what response do they cause in the plant

The dark period can aid trichs that havent finished maturing ie are clear..while preserving cloudy or already amber trichs (light degradation) the plant is still maturing in this dark period and hormones are building
Uvb increases certain precursors through uvr8 receptor activation
Thats as far as i know about the workings. Im no plant bio expert

but maybe after a period of darkness, a period of all light will make the plant produce even more to try and protect

Seems contradictory

BobCajun · Feb 15, 2016

0james0 said:
I've read plenty on the lights off for 24-72 hours before harvest. I've nearly always done it and I do believe it brings out the event in them.

Got a new theory, given that the THC and resin is produced in part to act as sunscreen. The darkness stresses the plant to make it more of it, but maybe after a period of darkness, a period of all light will make the plant produce even more to try and protect itself from the unexpected sun?

I'm now at the period of 24 hours darkness done and wondering if before I waste my time trying this, if anyone has before?

No don't put the light back on. Plants take 24 hours to metabolize all of their stored starch, and obviously smoking starch is not a good thing. But then if you turned the light back on you'd get starched up again. No point going beyond 24 hours darkness though. I've read posts that said it made no difference even with several days. Also I've read that THC is highest just before dawn so they don't need light shining to make it.

What I do is start harvesting and trimming them at 24 hours, cutting off branches one by one as I complete the trimming. So some of them get a few hours longer in the dark. I find cleaning buds is easiest when they're still fresh.

Resinhound · Feb 15, 2016

BobCajun said:
No don't put the light back on. Plants take 24 hours to metabolize all of their stored starch, and obviously smoking starch is not a good thing. But then if you turned the light back on you'd get starched up again. No point going beyond 24 hours darkness though. I've read posts that said it made no difference even with several days. Also I've read that THC is highest just before dawn so they don't need light shining to make it.

What I do is start harvesting and trimming them at 24 hours, cutting off branches one by one as I complete the trimming. So some of them get a few hours longer in the dark. I find cleaning buds is easiest when they're still fresh.

See what I mean...lol.The whole 24hours to use all the starches bullshit,not based on facts,just anecdotal.The cannabis industry is the only place you will hear stuff like this OP.

churchhaze · Feb 19, 2016

Resinhound said:
See what I mean...lol.The whole 24hours to use all the starches bullshit,not based on facts,just anecdotal.The cannabis industry is the only place you will hear stuff like this OP.

It's true. Plants store just enough starch in their leaves' chloroplasts to make it through the night period. At the end of the night, nearly all of this leaf starch is used up, and if the darkness continues, the plant will go dormant and stop respiration all together.

Chopping before the lights come on does make a small difference. 12 hours of darkness will do the same thing as 24 hours of darkness.

Resinhound · Feb 19, 2016

churchhaze said:
It's true. Plants store just enough starch in their leaves' chloroplasts to make it through the night period. At the end of the night, nearly all of this leaf starch is used up, and if the darkness continues, the plant will go dormant and stop respiration all together.

Chopping before the lights come on does make a small difference. 12 hours of darkness will do the same thing as 24 hours of darkness.

Plants seem to utilize starches from the leaves under 24 hour light just fine.I can see that dark periods would increase the use of stored starches as there is no Photosynthesis going on.Wether that raises thc levels etc is pure conjecture.

BobCajun · Feb 19, 2016

Here's something that has negative effects on potency; going back to a long day cycle at the end of flowering. I only gave it 3 days of that and it came out low potency. Could have been something else but could have been that too. I think it might help to go to even shorter days at the end to force ripening. Maybe you only get max potency when days get shorter at the end. They don't really seem to ripen completely under 12/12. I can still see new flowers coming out. Probably need to go down to 10 hours, maybe even 9 for the last few days.

churchhaze · Feb 19, 2016

Resinhound said:
Plants seem to utilize starches from the leaves under 24 hour light just fine.I can see that dark periods would increase the use of stored starches as there is no Photosynthesis going on.Wether that raises thc levels etc is pure conjecture.

That's also not true. Under 24hour light, leaves will always be saturated with starch. If you don't believe this, you can easily test for yourself by doing an iodine test.

Resinhound · Feb 19, 2016

Thats interesting about the iodine test,didnt know about that.However I can tell you that plants seem to utilize whats in the leaves under 24hour light.I see it all the time or what looks like it anyway.Yellowing fans in late flower irrespective of nitrogen.I will try the iodine test this run to verify.

Pretty sure cannabis is a c3 plant,every study ive looked at says these plants dont require a dark period,If you have an actual study that says otherwise id like to see it.

Perhaps you should try growing an auto under 24 hour light,then youll see exactly what I mean.

churchhaze · Feb 19, 2016

Resinhound said:
Thats interesting about the iodine test,didnt know about that.However I can tell you that plants seem to utilize whats in the leaves under 24hour light.I see it all the time or what looks like it anyway.Yellowing fans in late flower irrespective of nitrogen.I will try the iodine test this run to verify.

Pretty sure cannabis is a c3 plant,every study ive looked at says these plants dont require a dark period,If you have an actual study that says otherwise id like to see it.

You're thinking of respiration of sugars, not starch. I do 24 hour days in veg too so I know they don't need a dark period. Starch is used to store sugars for long term so they can be broken down into sugars later. The point of leaf starch in particular is so the plants have something to break down into sugars at night.

Resinhound · Feb 19, 2016

churchhaze said:
You're thinking of respiration of sugars, not starch. I do 24 hour days in veg too so I know they don't need a dark period. Starch is used to store sugars for long term so they can be broken down into sugars. The point of leaf starch in particular is so the plants have something to break down into sugars at night.

Starches are complex carbohydrates (sugars) I was under the impression they are one and the same.

churchhaze · Feb 19, 2016

Resinhound said:
Starches are complex carbohydrates (sugars) I was under the impression they are one and the same.

They are both carbohydrates, but starches need to be broken down before they can be used in respiration. Starches in other places (like fruits) are used for other reasons than leaf starch. Apples, for example, have the majority of their carbs partitioned as starch until they're ripe. A lot of fruits and flowers do something like this, storing a lot of carbs as starch until a climax period where it breaks it all down at once into sugars or nectar (tobacco floral nectaries do this http://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=16978&context=rtd).

Resinhound · Feb 19, 2016

Ok cool I got ya.Thanks church.Still wondering how this affects potency.Its going to take me a while to read through this dissertation

BobCajun · Feb 19, 2016

The 24 hours dark probably won't improve potency much, but I just think starch would cause harshness so why not let the plant break it down and use it up? It doesn't take long anyway. It's just an extra touch that may be helpful. It may reduce weight some, idk. Probably not much.

wyomingbarber · Mar 1, 2016

Why do this at all? Your plants are still alive for quite awhile after chopped and your hanging them upside down in the dark anyways. Does the plant stop processing starches as soon as it's removed from root structures?

saiyaneye · Mar 1, 2016

My question is what if all your plants dont end at the same time? What do you guys do? Smell cannot be an issue with me, my carbon scrubber is working great. A box with flex duct to the tent. Passive air through the box to the tent and out of the carbon filter?

BobCajun · Mar 2, 2016

saiyaneye said:
My question is what if all your plants dont end at the same time? What do you guys do? Smell cannot be an issue with me, my carbon scrubber is working great. A box with flex duct to the tent. Passive air through the box to the tent and out of the carbon filter?

Just harvest right before the lights come on. They will have had 12 hours of dark and will have burned most of the starch. 24 is just a figure I got when I read about how they tested leaves for starch using iodine and they said that 24 hours dark was needed to get rid of all the starch.

ky man · Mar 5, 2016

I don't know shit about growing indoors,but have friends that do and they always told me that it did not mader how long the plant was left in the dark or light.that it came out the same,,but it could be that they just wount to chop couse its not a legal state and that's why I would chop asap.And I also can not spell for shit eather..LOL

Lights off 24 hours before harvest - then back on again?

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