Live Stoner Chat The science of leaf pruning/defoliation?

[DTOM420]

I want to learn about the science behind leaf pruning - a.k.a. defoliation - so that I can make better decisions on which leaves to remove. I’m hoping that someone can give some science-based information on what particular leaves do and how to look at the structure of a branch and determine which leaves will be the most beneficial to leave and which ones are best to go.

I have a couple plants that are very dense but they’re 36 days into flower and I’d like to make good choices as I remove fan leaves. I don’t JUST want to use the shade they produce as the sole determining factor when choosing them for removal. So......

Question 1: Is a fan leaf exiting below a bud site crucial to the formation of that bud; or are the smaller leaves and sugar leaves that grow from the bud site sufficient for the collection of light once the bud is fairly well established? I do know that fan leaves are crucial in the formation of bud sites as the plant begins the flowering cycle but I don’t know if that importance remains throughout flower or lessens as the bud is established and creates additional leaves.

Here’s a picture of a bud site in early flower. I think around 7-10 days into flower. The fan leaf indicated by the red arrows was shading another branch. However, it’s connected to a forming bud (circled in yellow in 2nd picture) and I wasn’t sure of the ramifications to the bud if I snipped the fan leaf. So, I’m trying to get a handle on how to make this choice an informed one.

Here’s a flower much further along. If the leaves indicated by the red arrows are removed, will the bud still grow well just using those smaller leaves and sugar leaves for light gathering?

Question 2: In the vegetative growth stage, will the removal of 1 fan leaf at an internode disrupt future formation of a bud site, since there’s still (usually) another fan leaf remaining at that internode/potential bud site? I have read some articles saying that a good technique to defoliation is to remove one fan leaf at each internode and working up or down the branch in a sort of spiral staircase pattern, removing one leaf at a time.

My biggest interest in this is during the flower stage, of course. I know there are many theories on defoliation during flower; stretching from those that say don’t remove ANY leaves to those that strip off all the fan leaves. So, I’m sure there’ll be differing opinions on all this. That’s ok. But what I’m most interested in is the science behind how/when/if those fan leaves play really vital roles in flower development in mid and late flower.

 

[Paradiso]

I have no idea but it's a great question. I've been wondering about the same sort of questions myself.
I tend to go easy on defoliation and use shading as the main criteria but wtf do I know?

 

[DTOM420]

I have no idea but it's a great question. I've been wondering about the same sort of questions myself.
I tend to go easy on defoliation and use shading as the main criteria but wtf do I know?

That’s essentially what I’ve been doing also. Just thought to myself, “This seems kinda ham-fisted and there’s GOT to be a better way.” I’ve been spending too much time listening to the KIS Organics podcasts and getting wrapped up in the science behind all this. Glad I’m not the only one wondering about it!

 

[BII]

Some related questions that might be resolved along the way:
1) What is exposure of more buds to more light, presumably the main goal of defoliation, actually expected to do (and what has it been proven to do)? Do bud sites getting increased direct light exposure result in more buds, bigger buds, more cannabinoids production, higher quality product, quicker or longer harvests, etc.?
2) How important is biomass, having lots of leaves and biomass? Is removing functional leaves simply counter-productive, decreasing the plant's available and stored energy (sugars)?

 

[Simplicio]

An opinion from https://www.rollitup.org/t/is-lollipopping-really-worth-it-does-it-increase-yield.946868/page-3
that I agree with:

"Cutting off green healthy leaves is the biggest stoner myths that exists.

Nitrogen and many other nutrients are translocatable, i.e light hitting any green and growing leaf will translocate carbs and some other nutrients wherever the plant needs it. If it is a green and growing leaf it is there for a reason. There comes a time in any plants life (be it a flower, weed, or redwood tree) where the requirements of that leaf nutrient-wise, are more than that leaf can produce. i.e. the plant says "ok, leaf, you worked well for a while but now you are a bit shaded and not contributing to the overall good of this plant system. You are taking more energy to sustain than you produce for the good of the plant, no slackers, so you are outta here". And that leaf then yellows out and falls off all on it's own, after the plant has extracted whatever assimilated goodies the leaf has on board.

There is an energy cost to the plant (any plant) in photosynthesizing, converting and assimilating all the nutrients, and over millions of years I think plants have gotten pretty good at knowing what they need. MJ is just another plant.

Continue to strip off nice big green leaves, you will not increase your bottom line in any way. Sure less popcorn, but overall you will max out at less final product.

No other plant in commercial production is vandalized in this way, because it is Bullshit stoner reasoning that "light has to hit the budsites".

And that's just Bullshit, backed in no way by science.

Got an airflow / mildew issue.... then deleafing can certainly help in that situation. But it is a reactive response, one that should have been avoided in the first place. Need to tweek environment, maybe grow plants that are not dense cabbages, etc.

Anyway to me stripping leaves is like medieval bloodletting where "doctors" (actually called barbers) would drain blood from sick people trying to get rid of the poisoned blood. Sick people need all the blood they have, just as our plants need leaves.

41 years (now in 60's) of working in botany, soil science, and gardening gives me a pretty objective point of reference. And all I can say is MJ is about the easiest plant on the face of the earth to grow. For any aspiring growers, it's easy, but forget the VooDoo science, it will derail you."

 

[Paradiso]

An opposing point of view: https://www.growweedeasy.com/marijuana-defoliation-tutorial

... "Opponents often have arguments like, "PLANTS NEED THOSE LEAVES! If they didn't, they wouldn't be there.

Or my all-time favorite, "I have a friend who used to grow, and he insists that will hurt the plant."

Yet the saddest part of all is how so few people are willing to look at the evidence.

In some ways, I almost would prefer the rest of the growing world keep up their ill-advised lollipopping, removing growing tips, and other low-yield techniques. The defoliation technique has been loudly condemned by "experienced" growers for decades. Nevertheless, I am determined to educate other growers about defoliating and let them see the results for themselves."...

I sure as hell don't know but I haven't come across anything but good info on GrowWeedEasy

 

[DTOM420]

An opinion from https://www.rollitup.org/t/is-lollipopping-really-worth-it-does-it-increase-yield.946868/page-3
that I agree with:

"Cutting off green healthy leaves is the biggest stoner myths that exists.

Nitrogen and many other nutrients are translocatable, i.e light hitting any green and growing leaf will translocate carbs and some other nutrients wherever the plant needs it. If it is a green and growing leaf it is there for a reason. There comes a time in any plants life (be it a flower, weed, or redwood tree) where the requirements of that leaf nutrient-wise, are more than that leaf can produce. i.e. the plant says "ok, leaf, you worked well for a while but now you are a bit shaded and not contributing to the overall good of this plant system. You are taking more energy to sustain than you produce for the good of the plant, no slackers, so you are outta here". And that leaf then yellows out and falls off all on it's own, after the plant has extracted whatever assimilated goodies the leaf has on board.

There is an energy cost to the plant (any plant) in photosynthesizing, converting and assimilating all the nutrients, and over millions of years I think plants have gotten pretty good at knowing what they need. MJ is just another plant.

Continue to strip off nice big green leaves, you will not increase your bottom line in any way. Sure less popcorn, but overall you will max out at less final product.

No other plant in commercial production is vandalized in this way, because it is Bullshit stoner reasoning that "light has to hit the budsites".

And that's just Bullshit, backed in no way by science.

Got an airflow / mildew issue.... then deleafing can certainly help in that situation. But it is a reactive response, one that should have been avoided in the first place. Need to tweek environment, maybe grow plants that are not dense cabbages, etc.

Anyway to me stripping leaves is like medieval bloodletting where "doctors" (actually called barbers) would drain blood from sick people trying to get rid of the poisoned blood. Sick people need all the blood they have, just as our plants need leaves.

41 years (now in 60's) of working in botany, soil science, and gardening gives me a pretty objective point of reference. And all I can say is MJ is about the easiest plant on the face of the earth to grow. For any aspiring growers, it's easy, but forget the VooDoo science, it will derail you."

So, I obviously don’t know or I wouldn’t have started this thread and I mean this with tons of respect but that argument doesn’t make much sense to me either. Maybe you can explain it better to me. I want to make it clear that I’m not arguing here - I’m trying to understand and discuss. But the statement you quoted doesn’t make sense, to me, when I read it and look at the logic behind the statements. So, I’m going to lay out the problems I have with what he/she wrote below. This is NOT directed at you (@Simplicio) and I hope you don’t take offense as I certainly don’t mean any. Please feel free to let me know if I’m missing something or misunderstood something he wrote; or if there’s something wrong with MY logic in rebutting his statement.

The quote talks a lot about the plant’s natural cycle (“....plant’s have gotten pretty good at knowing what they need.”) but there’s a HUGE difference between what a cannabis plant’s natural desire and goals are and what we as growers are trying to achieve. A modern cannabis grower is trying to manipulate the plant and either force or coax it to do what THEY want it to do in order to produce the most flower it possibly can with the most trichomes it possibly can. In nature, the plant doesn’t have the same goals necessarily, imo. I think it’s goal is to survive and achieve reproduction. If it achieves that goal, it’s a success; from the plant’s perspective. In that case, a plant would naturally produce more leaves than it actually needs because it will lose some to external forces like the elements, insects and animals and even disease. Seems like an abundance of leaves is a good evolutionary defense. The premise of the guy’s whole argument is that the plant has a perfect system; which it does if our goal was simply to produce at least one seed to start another generation, like the plant’s goal. But since our goal is very different, I don’t see how his argument absolutely applies here.

Also, cannabis certainly didn’t evolve to grow in the highly optimized media and environments that we provide our plants. Again, they evolved to survive in crappy soil and harsh environments. So, it’s certainly not unreasonable (as the author implies) that some of the rules might change or that some of the plant’s natural characteristics are counterproductive to achieving our goals. Especially when we are providing them with every conceivable thing they could ever need or want - a situation that would never occur in nature

Then, the author claims that defoliation, “won’t increase your bottom line” as if there was irrefutable proof of this. If that was such a ‘fact’ and based solely on stoner science, why is it that so many commercial grows DO employ some sort of defoliation? There’s certainly plenty of anecdotal evidence that proper defoliation DOES improve yield or it wouldn’t be so commonly used. Now, that’s not to say there’s scientific proof which I would prefer; but until I can find some one way or another it seems like the anecdotal evidence in favor of at least some sort of defoliation being beneficial outweighs the evidence to the contrary. No? I don’t mean you or anyone has to buy into it but there sure do seem to be more growers doing some sort of defoliation than those who don’t.

“No other plant in commercial production gets vandalized in this way.” So? Lmao! What does that prove? Talk about stoner science! Lol! In fact, that the statement is not true and only serves to prove the author’s ignorance. Cowpeas produce a 50% larger yield when defoliate in flower, to name one. But even if it was, who cares and what does it have to do with anything? Plants are grown based on their unique characteristics not on how we grow OTHER plants. Lol! We do whatever we need to do with plants to get the outcome we want, from breeding, crossing species, grafting plants together, etc, etc. Cannabis is a pretty unique plant from a growing/harvesting perspective so we would naturally do things differently than many/most other commercial crops. This is where the guy (original author) really started to lose my respect and got me questioning/re-examining the whole statement. THEN, he claims that people are saying, “light has to hit the budsites” but that’s NOT what people say. What I’m pretty sure they’re saying is that the buds are BETTER when they get direct light exposure. <—That’s a VERY different thing and it certainly seems to make sense. Where do we find the biggest fattest buds? In the most light exposed areas. Where do we find the smallest and most undeveloped buds? In the most shaded areas. Is this scientific proof? Nope. But it’s sure some pretty strong anecdotal evidence. Again, from the plant’s perspective, a tiny bud (that’s useless to us) is just as viable to create its ultimate goal of a seed as a cluster of calyxes on an upper branch. That’s not OUR goal, though.

Certainly nothing wrong with being anti-defoliation and choosing to let them grow out naturally; but THIS author’s reasoning is laughable and the way he lays out his case has zero basis in real science and deductive reasoning and is, itself, the very definition of stoner science. Simply saying (essentially) ‘nature knows best so you’re stupid to do it differently’ is ridiculous. If that were the case we’d be utilizing nothing but landrace strains with larfy buds that require a Cheech & Chong sized joint to get medicated. If nature held ALL the answers herself, we wouldn’t enjoy all the flavors and varied medicinal benefits that breeders have and are giving us today. Manipulation of plants to achieve desired outcomes are an agricultural practice as old as farming itself. Manipulation is the key that unlocks mother nature’s treasure chest. As an old hippie myself I can say that the author of this original statement is spouting nothing but hippie nonsense. Lol!

 

[DTOM420]

Some related questions that might be resolved along the way:
1) What is exposure of more buds to more light, presumably the main goal of defoliation, actually expected to do (and what has it been proven to do)? Do bud sites getting increased direct light exposure result in more buds, bigger buds, more cannabinoids production, higher quality product, quicker or longer harvests, etc.?
2) How important is biomass, having lots of leaves and biomass? Is removing functional leaves simply counter-productive, decreasing the plant's available and stored energy (sugars)?

Interesting questions! Question 1 is essentially what I’m wondering - maybe more eloquently phrased than my own question. Lol! Hope we eventually get some answers. I suggested the topic to Tad Hussey for his podcast and he replied that he has an upcoming interview that will be touching on it. So, when it comes out, I’ll post it here. Thanks @BII !!

 

[Mikis]

This is a little off topic, but also a little on lol!!
Instead of removing the bigger leaves, pinch the stem and turn the leaf down 90 degrees! The lower areas that were shaded will now recieve more light and the fan leaf that was turned will also still receive light and turn it into usable energy for the plant! ✌✌

 

[BII]

This is a little off topic, but also a little on lol!!
Instead of removing the bigger leaves, pinch the stem and turn the leaf down 90 degrees! The lower areas that were shaded will now recieve more light and the fan leaf that was turned will also still receive light and turn it into usable energy for the plant! ✌✌

Other than pinching (stressing/damaging) the stem, this seems to be regular leaf tucking?