18-6 last 10 days of harvest?

I have heard from a well know breeder and commercial grower that he likes to flip his plants to 18-6 in the last 10 days of flower right before harvest. The reason stated is that it helps make bud swell up even more at the end. I am actually using his plants so i would believe he has stress tested these to the max as he is a very detail oriented breeder.

I have heard a few others that like the idea as well still it freaks me out. These plants look so awesome if they herm I am going to freak the fuck out. so any ideas on this.

Thanks Dono

P.S. the breeder is Irie Genetics

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Autos or photos?
What’s the pheno?
What light system are you using and what is the medium?
Also, what nutes, if any, please?
Inside or outside?

@GixxGrows sounds like Folly to me!

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inside, Orangegasm, photo, MHydro SP300, soil

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I’m struggling at the moment, so I’m trying to understand the why one would do this? I guess the only way to find out is to do it. Try a few? Take some clones to CYA?

kmac03 i found a video where Rasta Jeff was talking about this. So if interested give it a look you too cknugz. the questions begin at time stamp 14;44

He has been doing this a long time was part of the first dispensary in Pueblo Colorado, he breeds some straight fire runs 2 large commercial grows and of course the podcast. He is no beginner to say the least. But that said it still does sound like voodoo LOL

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Everything sounds like it’s full of fear until we just do it. I never believe anyone until I do it myself anyway. :rofl::v:


Seem to me they would go back in to veg

Agreed. But, what if hermed? Cut back and start over?

Try it with one plant and do the rest tried-and-true

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Someone with some sense. Thank you. The suspense truly was killing me.

@GixxGrows this works. It wouldn’t matter if your plants did begin to herm in the last few weeks before harvest because they wouldn’t have time to seed anyway and all of the nutrients would still be going to the flowers.

It takes 2 to 3 weeks for the hormones to change before any real revegging starts. That late into flower they are so full of ethylene that all the light schedule change will do is give them more light to use for photosynthesis and growth.

The most common issue with this is foxtailing because of the extra heat and high intensity light in flower. Foxtails are harmless as long as you pay close attention to the buds under the foxtails and harvest when they are mature and not the foxtail buds.

My personal issue with this is it allows the plant to store more starches which, in my opinion, is counter productive. It also increases the time needed for cure to break down the starches/chlorophyll. Another possible issue is with the increased vaporization and off gassing of terpenes because of the increased temperatures and high intensity light. This would in turn decrease perceived potency and medicinal efficacy. Of course, this can be curbed with proper ventilation and air conditioning but most home growers struggle keeping temperatures stable at the normal 12/12. If you do the 18/6 pre harvest I would personally suggest going back to 12/12 a day or two before harvest and do your dark time pre harvest to minimize potential terpene loss.


So, I’m inferring from this that starches become terpenes and if not broken down properly, instead of terpenes I get mold/mildew instead? I’m asking as I “see” some sort of chemical process visually in your words.

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@kmac03 no starches do not become terpenes. Terpenes are actually produced by C02 respiration where carbon is stripped from the C02 and then recomcombined into hydrocarbons called isoprenes.

Starch stores are there to store sugars and nutrients for the plant to use to build and repair itself during the dark time. So the less dark time there is the more starches and nutrients get stored in the leaves.

Having a high brix content in cannabis can be a good thing as the sugars are used for energy for the plant to grow and produce a hefty harvest and they can even give the cannabis a better sweeter flavor. This, of course, is only if you survive the cure.

The higher the starch/sugar content in your plants when drying and curing the faster bacteria can breed because they have more food to eat. The same goes for certain species of mold and mildew. It also effects the rate at which chloroplasts and thylakoids break down. Sugars protect the chloroplasts and thylakoids and stabilize the membrane which makes it take much longer to break down chlorophyll.

So there are benefits to it if done right, but in my personal opinion the extra cure time and increased risk of mold/mildew/bacterial issues it isn’t worth it. Especially for the average home grower that doesn’t have the clean room that would be necessary to get a good dry and cure that would pass local/state microbe and contaminant tests.


@kmac03 I forgot to mention above about terpenes that all forms of isoprenes such as terpenes, mono terpenes, sesquiterpenes, etc… are volatile hydrocarbons which means they vaporize and off gas at low temperatures. Just a mild 70f day is all it takes for them to start vaporizing. That’s why you always get the strongest smell from your garden on warm days but on colder days you don’t get much smell at all because they aren’t vaporizing or off gassing as much.


well im jumping in with both feet hoping for the best. As stated i could do a few with this technique and the rest with out. I don’t have enough rooms for this I wish i did but my other tent has auto’s in it right now waiting for this room to be cleared.

@MDBuds Thanks for your reply. I already had turned my lights down to about %70 my room stays at about 72-78 usually 75.

Next Friday is chopy chopy day. One week from today.

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Full moon is on the 24th, you might want to consider waiting the extra few days

@GixxGrows don’t forget to cut back the light hours right at the last few days so you can build some terpenes back up. I even do it with my autos. 24-48 hours dark time helps to preserve them before the chop but photosynthesis is still needed to help build them back up. Going to 12/12 or even 10/14 or 8/16 for the last few days will help burn off some of the extra sugars and build some terpenes back up. Happy growing man and good luck. Hope this works for you. :v::call_me_hand::metal:

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