How Much Does Harvesting In Morning vs Night Effect Potency?

Grow Cycle Harvesting
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I have read that it is best to harvest cannabis at sunrise (if outdoor) or right before/after the grow lights come on (if indoor). This is because they say that the light damages terpenes and trichomes and overnight the terps and potency increase again. Or something along those lines.

However, when I try to figure out exactly how much of an effect this has or try to find any studies on this, I can’t seem to find anything. I do believe it is true but I have no idea exactly how much of an effect it has (which may obviously vary depending on light exposure). Does anyone know more about this or have links to actual scientific research on the subject?

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I have always thought of it as a heat issue. Some terpenes evaporate in the mid-70…so with a light on in a tent it is warm. We also know that light is bad for terpenes and THC in storage…so kind of makes sense.

I could not find any studies for this specifically, but many book references. There are many studies on post harvest preservation of terpenes. One common step is get harvest to a cool dark area asap. Gonna check back to see if anyone can find a study

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I am pretty sure it is more of a light issue than heat although I suspect heat is a secondary factor. As you had mentioned, it is well known that light will destroy any type of psychoactive substance over time and this is why the drying room should be kept dark. Even if your dry room is 60 degrees it is advised to keep it dark.

Based on what we know about light it is a given that it will degrade terpenes. The question is how much does it effect potency between morning and evening.

Like is my plant 5 percent more potent at sunrise than it is in the evening? 20 percent? 50 percent? I have never found any real numbers, not even a ballpark estimate. In theory this should be a relatively easy thing to study and I am surprised it is still unknown considering cannabis is the number one cash crop.

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I think there is some research on this topic on YouTube. You’d think with all the bro-science it would be easy to find somebody doing a study in terpenes.
I prefer to do a wet defoliation a day before harvest and limit my cuts to old dried out and low level leaves. Then the day of harvest I cut within the first hour of sunrise.

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Thanks for the video, I love the perfect gardens show that guy has alot of great knowledge.

I just found one study that was very descriptive although it only measured THC and other cannabinoids. It didn’t measure terpenes which may degrade more quickly than cannabinoids. Also this was on harvested plant material rather than the plant itself.

Their study concluded that the bud degraded in potency by about 0.5% every hour that it was exposed to sunlight (in this case it was produced artificially which I think was foolish).

I think the experiment could have been done better but I think it sheds light on some things. If direct sunlight only has about a 0.5% effect per hour then I imagine the difference in potency between sunrise vs sunset is probably around 5% to 10%. Meaning if your bud is 20% THC at sunrise it will probably be 18% or 19% THC at sunset. Not really a huge difference.

Alot of times I panic if I get up later than sunrise on a day that I am harvesting but it probably doesn’t make a huge difference.

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Maybe it is a “zero sum gain” decrease % offset with more volume growth.

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I don’t think it is a zero sum game otherwise your cannabis wouldn’t get you high. I think it is more like 2 steps forward, 1 step back. The potency goes 2 steps forward at night and 1 step back during the day.

The volume of the buds will definitely be a factor because the exterior of the bud will naturally be most effected. So a huge bud that has most of its trichomes buried inside of the bud rather than on or near the surface would be less effected by light.

Now if you excuse me I need to go chop down my Pineapple Express. It is 6am here and the daylight is coming!

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Dr Bugbee has studied cannabis more than anyone at this point.

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I’ll check the video out later although it doesn’t really do anything to answer the original question which is difference in potency between morning vs evening.

Using 48 hours of darkness doesn’t really apply to me anyway as I am an outdoor grower. Most of my plants are too large to bring inside, even IF my landlord would allow it, and I know he wouldn’t. Half of my plants are in the ground and cannot be moved. Most of my plants in pots already have their roots growing out of the pot and deep into the ground.

So while the 48 hours of darkness may make sense for an indoor grower, it is virtually impossible for an outdoor grower like me. Most outdoor growers are the same way unless they just have a few tiny container plants and own a home. I just rent a bedroom and I’m not trying to get kicked out, it was difficult enough talking my landlord into letting me grow pot in the first place! Lol

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I just watched the video. Before watching I assumed he was arguing in favor of 48 hours of darkness since I hear it so often, but apparently he is arguing against 48 hours of darkness.

He sounds very intelligent although he misses the mark in some ways. And I’m not arguing in favor of the 48 hour thing, I would have to do experiments to form a solid opinion either way (or at least see solid research on it).

He states that the darkness would be bad because the plant uses photosynthesis to generate terpenes. This is true, but he is also not mentioning the fact that we KNOW sunlight decreases potency - roughly 0.5% per hour in direct sunlight based on that other study I found.

Overall I think keeping the same light cycle is better UNLESS you are trying to intentionally stress the plant late flower. That guy on perfect gardens talked about how many expert growers use stress to make their plants produce more resin. That guy won big competitions this way so I assume there may be something to it.

In terms of the terpenes and trichomes though, basic logic should dictate that the plant’s photosynthesis produces more trichomes and terpenes per day than it loses per day. Although I don’t think the energy is lost in the dark cycle, I think the plant is kind of like a battery that can store the energy from photosynthesis kind of like how solar panels can store energy for later use. 48 hours of darkness may or may not cause the plant to run out of energy, I honestly don’t know.

I do suspect potency is lower at sunset than sunrise and that the energy stored from photosynthesis helps the plant push the potency higher during the dark cycle, whereas it may reduce very slightly during the day. That’s just my theory though. Really not much research on the subject but I enjoy doing my own little experiments.

Had a good harvest this morning. Now my bedroom smells like freshly cut pineapples… and pot.

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We’ve seen fads come and go re: prep for harvest. Splitting stems, ice baths etc. None of them have shown a measurable improvement of the finished product.

I will also point out that after harvest and until dry, plant material will still undergo photosynthesis. Personally I don’t care about a reduction in potency because they’re already stupid strong. I’m chasing terpenes myself. I’d trade potency for stinky any day.

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He is the leading PHD studying cannabis hes been funded by NSA to study plant growth for the lest few decades and is professor Director of the Crop Physiology Lab at utah state.

I am just going to go with he knows more than me or you or any YouTube bros.
Theres lots of vids if him talking about cannabis

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That’s a valid point although light will degrade both cannabinoids and terpenes.

That is very interesting that the plant material produces photosynthesis after chopping but I question how much and for how long. Also there would be a big difference if doing wet trim vs hanging the whole plant upside down.

It is generally accepted that the drying room should be dark. And in studies where they shine light on buds, potency decreases. MAYBE this would not hold true with freshly cut buds due to photosynthesis but I am doubtful that it would.

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“Funded by the NSA”

For starters, I wouldn’t be quick to trust anyone funded by the NSA, or really any 3 letter agency, for that matter. It wasn’t very long ago that government agencies were throwing my family and friends in jail.

Making lots of youtube videos doesn’t mean much, you could say the same for plenty of idiots. Having a PhD is a big accomplishment though, I’ll give him that. But I know plenty of people with PhD’s who know very little about cannabis and some of them I got high for the first time.

As far as my own credentials - my family used to manage one of the largest cannabis distribution networks in New England, back when it was still illegal and we had to bribe friends in those alphabet agencies. I was only moving between 5 and 25 pounds of cannabis per week, but the family member that I worked for was moving 300 to 500 pounds of cannabis per week when we were in our prime. We were the ones who made Jack Herer extremely popular in New England between roughly 10 and 15 years ago.

My username Mastrosso is my mother’s maiden name, which translates to Masterbone or “Master of all the Bones”, and I am the first born son of the Mastrosso - Coscina family. According to legend, Mastrosso was one of the three men that started the 'Ndrangheta. Interpol considers the 'Ndrangheta to perhaps be the most internationally powerful organized crime network in the whole entire world. According to Interpol the 'Ndrangheta controls roughly 80 percent of the European cocaine trade and has active 'Ndrina (Italian families) in roughly 200 countries worldwide.

Roughly 8 years ago there was a RICO investigation targeting both my immediate family and extended family (and myself) involving State Police, DEA, FBI, IRS, ATF, and the Department of Homeland Security.

So I have some credentials as well and wouldn’t abandon all of my knowledge just because some guy with videos on youtube has a PhD. There are a thousand more people with PhDs stating that light will break down virtually any psychoactive compound whether it is THC, Cocaine, or LSD.

Also I wasn’t ever disagreeing with him in the first place as I don’t do the 48 hours of darkness and mentioned it is not suitable for my outdoor growing practices in the first place, for some reason you are acting like I disagree with him. The only thing I said that was even remotely in disagreement is that he missed the mark somewhat because he did not take into account some things that any cannabis scientist knows to be true - such as the fact that light breaks down psychoactive substances (and really just about anything) and you shouldn’t need a PhD to know that.

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:roll_eyes: Science bad, your amazing right got it.

Best of luck.

Responding to questions in forums is like your wife asking you if she looks fat in the dress.

Lesson learned peace out ILGM.

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I never said science is bad. My original post was specifically asking for actual research or data on the subject. Nor was I claiming to have the answers, which is why I was the one asking the questions. It is also “science” which states light breaks down most psychoactive substances and many other compounds.

Dr. Bugbee also mentions in the video that much of what he is saying is merely his own theories and that he doesn’t really have much research or data to back up what he is saying. So in his own words, what he is saying is purely conjecture and should not be accepted as a matter of fact quite yet.

The video was only indirectly related to the original post anyway, in a tangential sort of way. And again - I never explicitly disagreed with him I simply felt there might be more to the story and that he didn’t seem to be taking every single variable into account. That’s it and that’s all. There is no reason to engage in personal attacks just because I will not blindly believe someone that you choose to worship.

I am not going to engage in personal attacks against you because that would lower me down to your level and fail to result in anything productive towards the original question - how much does the potency in a cannabis plant vary between sunrise and sunset?