24-48 Hour Dark Period Before Harvesting

[tronN00dles]

Hey folks,

I see a lot of people throw this "24-48 hour dark period before chopping" concept around, although I haven't seen any proper science behind it. Has anyone done any controlled experiments with and without a prolonged dark period pre-harvest, and if so, did you notice a difference?

-tronN00dles

 

[nizmoKush]

I've done it and see no difference so I dont do it.

 

[Steviestash]

 

[Mañ'O'Green]

 

[armanidog]

It seems to me, if you shut off the lights, the plants basically slow way down and not much changes.

 

[CannabisMingus]

I've done it and see no difference so I dont do it.

 

[Bruce Campbell]

The basic science is that during darkness, photosynthesis and transpiration decrease but respiration continues/increases (basic description of plant respiration here). That is, plants switch to using the glucose produced during photosynthesis and O2 to provide energy. If you watch Bugbee's videos (youtube channel here), this is what he's referring to when he says photosynthesis efficiency goes negative at zero PPFD.

I would be careful with drawing any conclusions from Lost Leaf's lab results above since he wasn't able to do multiple samples to account for plant-to-plant variability, but the general experience from those who have done lab testing seems to be "no significant effect on cannabinoids, maybe a slight impact on terpenes."

The other theories are that lower carbs can give you a head start on the curing process, and that a darkness period can improve the appearance of buds and trichomes. But, those aren't things that would be measured by labs in typical cannabinoid and terpene profile tests - so, most of the reports are just anecdotal, and plenty have success with no dark periods.

Overall, I would probably say "harvest when the buds are finished and you have the time." If the buds are finished mid-week, but you don't have time until the weekend, then keep them in the dark for a few days so they don't over-develop.

 

[MR magoo]

Done before and after tests twice in years past. even took before and after shots. NO difference.

 

[pop22]

Another myth that deserves to die!