48 hours of darkness before harvest

Discussion in 'Subcool's Old School Organics' started by Daemonn789, Sep 10, 2012.


    Daemonn789 Active Member

    I've read things and talked to growers over the years and seen that many people move their plants into darkness for anywhere from 12-72 hours depending on who you ask. So, now I ask the weed nerds -

    Do any of you fine folks put your plants into a period of darkness before harvesting?

    And if so...

    What have been your results and own thoughts?


    Everyone else - does this method seem useful enough to use?

    dababydroman Well-Known Member

    they will continue to grow basically. and possibly ripen more. cant hurt. do it.

    thehole New Member

    No. No and no.

    You are better off giving your plants the full 12 hours of light those last days. The myth that darkness tricks the finished plant into producing more resin is just that, myth. A plant needs that 12 hours of light during the day in order to produce that resin at night.

    There IS NOT scientific proof this works, there is scientific proof it probably doesn't work.

    If you chose this route at least crank up the de-humidifier to keep the humidity down to 30% or so where it's suppose to be the last week.

    Daemonn789 Active Member

    People have tried it with mixed results - but yea make sure the humidity stays in check.
    Farmer.J likes this.

    dababydroman Well-Known Member

    the plant will grow or be alive for a couple of days if you leave it in the dark.. so i think its just like letting the plant use all its stored energy before chopping it
    GreenThumbsMcgee likes this.

    PeyoteReligion Well-Known Member

    "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 of Leiden.

    One of their discoveries has been that to keep the ripe plants in the dark before harvesting could increase their potency.SIMM’s growers separated a crop of mature plants, harvested half of them and kept the other half in absolute darkness for 72 hours before cutting and drying. Analysis of the resulting dried buds showed that some varieties had seen an increase of THC of up to 30%, while CBD and CBN remained the same."

    Thc degrades in light. Thc is used by the plant as a sunscreen, primarily to deflect UV-b which damages the molecule. The thrichomes are refracting sunlight away from the plant protecting it from the damaging uv-b. The plant produces these trichomes in the twilight hours before sunrise in order to protect itself from the sun. Extending this twilight dark period allows for the plant to continue producing thc without it being damaged by light.

    PeyoteReligion Well-Known Member

    You are wrong. Do research past page one on google.
    GreenThumbsMcgee likes this.

    Daemonn789 Active Member

    So the plot thickens... I recently harvested a few plushberry. Kept one in total darkness for 72 hrs. Harvested the rest the same day as the one in dark finished. The one in darkness definitely had a more wet and sticky feel to it. Can't say anything on the smoke and wont be getting these lab tested so its all anecdotal for me. I think I'll keep experimenthing though.
    Bestg4202 and GreenThumbsMcgee like this.

    Daemonn789 Active Member

    30% gains in any statistic is worth giving second looks at, thanks for the post!
    GreenThumbsMcgee likes this.

    CreedTaylor Member

    Remember study shows 30% increase in THC which is 10-25%. Not increasing total FLOWER THC by 30%. Not enough to make a difference.

    Oriah Well-Known Member

    Its takes a 15% thc bud to 18%... Fuck ill take it! lol:bigjoint:
    budman111, estee and GreenThumbsMcgee like this.

    Daemonn789 Active Member

    Also, if you run a perpetual where you're only pulling a few plants at a time for harvest, its easy to just throw em in a dark tent for 72 hours and rotate plants into the dark as you harvest. Just time appropriately so you aren't going weeks extra on strains that don't need it while they wait for their turn in the dark room. If it's 15% to 18% after just waiting an extra few days - why the fuck not?! You may not "feel" 3% or anything, but just knowing you are giving them an extra boost is a good feeling. If we are going to pull out all the stops to increase quality, looks like we might have to consider this technique.
    estee likes this.

    SpicySativa Well-Known Member

    Here's my theory:

    Terpenes are volatile. They evaporate into the air, and that's what we smell. Volatile compounds evaporate faster in higher temps. So the amount of terpenes is highest right before lights come on, because they are building up at a higher rate than they are evaporating. I harvest at the end of a dark cycle. I suppose an extra long dark cycle might push my theory to its max.
    budman111, estee and GreenThumbsMcgee like this.

    montanachadly Active Member

    I do the dark thing everytime but mostly cause im too lazy to chop it up the day it comes down i usually pull a few plants down at a time. My thought on this is the only way to get a real good scientific answer to this question would take alot of work. First off im sure that each genetic strain is different and reacts different to total darkness for extended time. It would be i think the best possible way to determine this take a few difft strains with 2 clones of each so there dna is identical grow them under the same conditions so theres no genetic drift or anything stress related harvest one and the other leave in the dark for a few days. Then take both to the lab get all the thc, cbd, cbn etc tested. But i have noticed that when i did this with clones the same the one left in the darker had bigger resin heads than the fresh harvested one. Beyond that i dont know which was more potent cause ive never sent the stuff to the lab. These next few rounds of TGA looking for keepers i will send to the lab to get tested. Maybe if i have the money i will do it with a couple of my chernobyl clones.

    IlovePlants Well-Known Member

    In the last week of flowering I move my plants to the "early flowering" side of the room. They are given less light, and are only left in darkness 18 hours before chopdown. I have never noticed an increase in yield any other way, in fact the yield is exactly the same, it just allows me to move plants into the more intense light earlier.

    If your plants are fading properly, they should be faded out by the time you get them down. What would be the point letting them spend extra time retrieving stored energy from spent photocells that contain no stored sugars? They like the rest at the end, because it more closely reflects the lack of fulltime sun. It tells the plant that now is the time to put everything and anything into flowering.

    I've harvested with 12, 16, 18, 20, 24, and 48 hours of darkness. The only difference I have every witnessed for myself was between 12 and 16 hours. The 16 hour buds were stickier and wetter over all. I harvest at 18 because I would assume that any additional sugar absorption to create thc would follow a bell curve of efficiency. It takes a while to make thc, besides the resting, the plant needs light to tell it to resist something.

    All I'm saying is this. How much energy does a plant keep stored when it thinks it's days are numbered? My experience says not that much, but then again my plants are fading by finish. I depend on fading to provide the best flavor possible, because, at this point, I'm very picky.

    TLDR; I fade my plants at finish and haven't noticed any difference. Maybe it works with green plants? The only real experience is first hand experience, try it for yourself and see what works for you and your set up.
    norcal mmj likes this.

    Daemonn789 Active Member

    I think from the SIMM study, 72 hrs is minimum to have actual affect. And then the idea is not to increase yield but to allow the chemical profile of the resin to change. It is known that light degrades THC and other chemicals/terpenes, so the theory is that 72 hours of darkness allows the resin heads to "ripen" to a point they otherwise would not get to with lights coming on. Do it at the end of harvest and only for the required 72 hrs to avoid mold from starting.
    estee likes this.

    GreenThumbsMcgee Well-Known Member

    You know, givin the scientific world we live in, i am quite suprised there hasn't been more conrolled and accurate testing done on these highly debated topics. It wouldn't take more then growing identical strains, one in 72hrs dark, one not, and have them tested. Do that test multiple times and average your numbers. At least if someone did this we wouldn't have to wade through 3feet of bullshit to get a reasonable answer to questions like this. Hell, as they say, "if you want something done right, do it yourself..." now, if only i could find the time!!!
    RockinDaGanja likes this.

    ukmrgreen Active Member

    hi i seen in a post on some site that reducing to 8 hours in the last few days then total darkness for the last day pri to harvest dont know if its true or what never triedit when i did a grow

    RockinDaGanja Well-Known Member

    Really. I agree. If you keep the same strains in the same medium, in the same growing environment. Same feeding schedule using clones. That would knock out most of the variables. The only thing is the temps and humidity at night but like you said run multiple test and average out the numbers.according too night time humidity and temps.
    Only if i had more time and space.
    GreenThumbsMcgee likes this.

    Shawns420 Active Member

    Think about it this way, Light and heat degrade the Trichomes witch will lower the THC and your Terpenes. I know this for sure when I pick my outdoor weed just before sun up, its way more sticky and Terpy cause the Trichomes have had all night to build its Terpenes, oils and such back up soon as the sun or light comes up/on they start to burn off,
    12-24 hours should be plenty longbow can go longer but I can't see more then 48 hours
    GreenThumbsMcgee likes this.

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