To defoliate or not?

[Billyn]

I usually defoliate just for better air circulation and to remove old leaves. I have always considered defoliation to be weakening the plant and force it to shift energy from buds to new leaves.
But maybe there will be some effect of hormones, reaction to stress. It is interesting that some strains themselves get rid of the lower leaves more than others after entering the flowering phase, some really significantly.

 

[944s2]

Up to week8 of bloom,
I remove fans that are blocking buds and leaves that are used up,,,
After week 8 then I don’t touch them ,,,,

 

[indagroove]

Defoliation is standard practice in the cotton industry, as there are studies which show conclusively that higher quality cotton flowers are a direct result of defoliation.

 

[imiubu]

Having low head way in my flower space, I begin training for low/ bushy gals at 4-5 nodes/ laterals (topped).
Early training of bonzai style plants lends to the defoliation of some fan leaves.
While plants are young, a carefully chosen leaf is plucked here and there most generally at the upper height.
Defoliating only those covering new growth as to encourage an even canopy at flowering time.

Typically there are 3 stages of defoliation here. #1 ^^ being the gentle and carefully chosen plucking stage while very young.
After a few days, the light is lifted, additional lamps are added and they get to reach for the sky for a few weeks.

#2 is when they have put on some foliage. These are pruned and defoliated heavily as I force them into their desired girlie figures.
This is where they get tied up too
Typically leaves are taken down the center and again, from the top.
A 'lolly popping' of sorts is performed.
The lighting unit is again lowered to encourage tighter lats.
At 22" and 24" respectively, these gals have their own screens per pot and today is their first day 12/12.
For time line reference: clones to solo cups on 8/31 and are currently in 7gal. for the finish.

In approx. 2-3 weeks a med. to heavy defol will occur again then; I will stop meddling and they will finish out w/ out intervention.
At this point, the leaves are cleared to shed light on the bud points . Remaining lowers that will not receive light are removed now also.
This helps with hand watering too

Without early defoliation; I end up with lopsided plants. This is not an optimum use of my tiny tent space (IME).
I have stripped them nearly nekkid and I've left them go natural.
I now 'leave' as many solar panels (sun leaves) as possible and still achieve my main goal.
This is just an example defoliation style and how it evolved over time for my personal grow space. YMMV

Heavy defoliation (again; IME) does require recovery time, so the gals get extra spa time and pampering afterwards.

 

[Chi13]

Defoliation is standard practice in the cotton industry, as there are studies which show conclusively that higher quality cotton flowers are a direct result of defoliation.

Well, cannabis isn't cotton. Some crops respond to defoliation whereas others do not.
Tomatoes for example ( I got this from the cannabis science consulting site):
Artificial defoliation of tomato plants by removing more than half of each leaflet, detachment of whole leaves from the lower three-quarters of the plant or of two leaves between each truss, caused up to 40% yield loss,
https://www.tandfonline.com/doi/abs/....1983.11515098

If cannabis holds true to the pattern demonstrated by the studies above, then YES you can safely prune or defoliate in small percentages (under 25%) to cut down on mold issues, without much damage to production.
If you remove much more than that you will reach a point at which crop producing ability is severely compromised.
https://cannabis-science-consulting....ation-studies/

 

[f-e]

Amazing they lost nothing at 25% yet 40% was lost with over half the leaves removed. I like the explanation, that the 25% was there for the bugs anyway. It's the remaining 75% the plant wants, and so removing over 33% of them would bring a loss around 40%. It's fairly linear seen in that light.
There is a difference. Both plants have leaves, yes. One has flowers that contain green parts likely to be of similar use to a leaf, while one has red fruit. I'm not sure how much a red fruit can contribute to photosynthesis. This 25-35% has been spoke about over the ages though. Any more said to be a bit of a shock.

 

[...CR500AF...]

After what i have read and seen i am going to say i do not defoliate, only a few here and there.
Do what works for ya i guess...

 

[@hempy]

Trying to discredit something you have little to no experience on is ignorant.

No ones forcing any one to Defoliate their plants but for us that do and have for many decades we do it because it works.

The science is clear.

It is backed by scientific research that shows that older plant leaves do not contribute as much to plant growth as new, smaller leaves, but instead, they become detrimental.

According to research, as plants grow, so does the size of their leaves. Older leaves become larger, thereby taking up even more water, sunlight and other nutrients even though their ability to support photosynthesis and other necessary processes is more limited. Defoliation aims to eliminate these older leaves and rejuvenate the cannabis plant.

Defoliation has been proven to boost the yields you can get from your cannabis garden. There are two angles to this: the first revolves around the plant hormone ethylene, which is known to lower yields because of its ability to trigger aging processes within plant cells.

Per nature’s design, ethylene is found in higher concentrations in older leaves and flowers, such as those at the lower ends of the cannabis plant. Defoliation effectively nips these leaves and flowers, triggering higher yields for the plant.

The second angle revolves around defoliation’s ability to increase the exposure of leaves to sunlight and air, which directly stimulates more photosynthesis, better growth and larger yields by harvest time.

 

[Chi13]

Trying to discredit something you have little to no experience on is ignorant.

No ones forcing any one to Defoliate their plants but for us that do and have for many decades we do it because it works.

The science is clear.

No, the science is not clear. I only wish it was.
Just because you have been practicing this for years does not mean it works as you describe. Unless you do a side by side experiment and compare clones of defoliated to undefoliated then you don't know it works.Your plants look great. My bet is that they'd be even better if you left the leaves on. I don't care whether you defoliate or not, but there is no evidence it works. I am happy to defoliate if someone can show me evidence, and by that I mean a proper controlled experiment where identical clones are used.
Some sites do advocate defoliation but they do not present any evidence that it works. I can understand doing it to reduce humidity and mould to an extent, but to say it increases yield makes no sense, even less when you are talking about a pure sativa.

The link you keep using is not a scientific link. It is a cannabis packaging material website, and it doesn't refer to any studies, just makes claims, "science shows", without backing them up. Other sites refute this claim.
Here's a few links.
https://cannabis-science-consulting....ation-studies/
https://www.cocoforcannabis.com/comm...-to-defoliate/
https://cannabiscultivation.institute/cannabis-defoliation-studies/

 

[@hempy]

The science is clear mate and so is your motivation.

How about you show us your best sat yielding indoor plant/. I have posted more than enough to prove my point.

Your arguing about something you clearly have not tried and yet we even see industry now is Defoliating plants to increase yield.

Read what i posted above again its based on science not hysteria or opinions.

 

[Chi13]

The science is clear mate and so is your motivation.

How about you show us your best sat yielding indoor plant/. I have posted more than enough to prove my point.

Your arguing about something you clearly have not tried and yet we even see industry now is Defoliating plants to increase yield.

Read what i posted above again its based on science not hysteria or opinions.

My motivation is to understand the plant we all grow, for my own benefit and for the cannabis community. I like science so when someone tells me something that does not make logical sense I look into it, as I have done with what you said about defoliation.

You haven't posted anything that has proved your point. You didn't even reference your last post, but I guess you got it from the cannabis packaging site? As to the studies you posted, one was about removing the centre bud to increase side branches (zero to do with defoliation)' the second one did not show either increase or decrease in seed productions (again not even about improving flower yield) and found no improvements anyway, and the third was from a site about cannabis packaging that quoted no scientific studies. I have taken the trouble to read what you have posted but you clearly haven't read the links I posted.

Lastly, please post some science around this topic if you have it. You haven't so far. You just keep repeating the science is there but not posting any actual science?

 

[Chi13]

This sums it up best for me (since no one is reading the links;
Defoliation: Myth vs Science

Glen Johnson

12 yrs in Commercial Cultivation / Industry Consultant / Founder - Cannabis Cultivation Institute

Published Jan 16, 2020
It may surprise you to hear, that there is a small but very dedicated group of cannabis farmers who are convinced they can increasing their crops by removing ALL the big leaves in the flower cycle. Believers in this myth call the technique Schwazzing.

If you're a Scientist, the same thing is called "Abscission Stress" and the data produced by this group generally shows that any stress in the flower cycle results in lost profits.

You might think that any technique claimed to make a significant difference in the production of Cannabis flowers would be important enough that it would be tested and proven with some real data. Hopefully this would be a University study with no financial gain from the data, but even a private study could be fine if it were done well and not just to promote some product.
So far.... NOTHING!

Real data on this issue - with cannabis - simply does not exist.

Both sides are absolutely adamant in their conviction about how correct they are, but no matter what either side "thinks" they know... neither one can prove it.

To a scientist, the first law of thermodynamics states, "you can't get something from nothing" and this is one of the single most foundational observations of the universe. According to this concept, the leaves capture light and convert it into sugar which is used as the chemical power source to build the body of the plant, so removing the leaves will remove the power to grow, and thus have a negative effect on plant growth.

Believers in the myth say this treatment will somehow magically make the plant bounce back and produce even larger flowers than it would have if left alone under the same conditions.

Call me crazy but this just seems to defy physics.

However, I've been wrong before, and physics has been wrong before.... so I'm willing to hear this out.

Believers typically say things like,

Removing the leaves gets more light on the buds and that makes them grow bigger.​

As a non-believer with a little science training and a lot of skepticism, I ask, "Why do you believe that?" To which they reply, "Because I've done it and it works!"

If you're a non-scientist, you might hear another grower say something like that and you simply take that word as gospel, without any supporting evidence, and that's all you need to create a FACT in your mind. This is a huge problem for our industry. The willingness of to believe something a friend says without any proof, is the very reason for the existence of the scientific method in the first place.

When I asked one grower to show me why he believes in this, here's what he said,

It's not bro-science, it's generations of growers passing down their knowledge of the plant. If you really are a cultivator you would know that pruning makes bigger final flowers​

That statement is the "poster child" for the scientific method.

Right here is the point where non-science and real science split off on two different paths. Non-scientist types are accustomed to simply taking the word of a good friend, or an obviously successful grower. Especially when the information "seems" like it might be plausible. But they have not yet learned the value of the need to see some supporting evidence. A person with a little scientific training knows to be skeptical and ask some basic questions.

Oh, you've done tests.... so tell me...

• How many plants were in each test group?
• How many plants were in the control group?
• What variables did you limit?
• How many strains did you test?
• How many times did you repeat the test and get the same results?
• What steps did you take to equalize the environment among the groups?
• Did you perform the test at different weeks in the flower cycle?
• How did you standardize the harvest time between the control and the test groups?
• How did you define the difference between "A" bud, larfy bud and trim?
• Did you define defoliation so all plants got exactly the same treatment?

All that questioning typically results in either; an angry tongue lashing (how dare you not believe me), or a stunned silent pause because a non-scientist will not have done any of those things.

Occasionally I talk with someone that swears they did all that, so I drop the bomb...

That's awesome... can you show me your data?​

NOT ONE PERSON, has ever produced a single scrap of actual data showing that they (or anyone) performed any kind of even moderately scientific trial - on Cannabis - that produced data that actually supports this weird Bro-Science myth. I've seen a little data on studies of defoliating other plants, but Cannabis is different, because once you enter the flower cycle, Cannabis is on a countdown that can't be stopped. Sure your plants would recover if you had a month to wait, but with Cannabis, you can't just pause the timer.
But guess what!

I can't show them my data either because this study has never been done!
Here's what I think I know because it "seems" plausible to me... When you flip the lights to 12/12, the race is on! Creating a stress event in the flower cycle is the equivalent of tripping a runner in the middle of a race. That runner can still get up and continue on to the finish, but it will either be later, or your flowers will be smaller. Longer time, or smaller flowers both equal money lost to a commercial farmer.

Yes, I realize that what "seems" to be right to me, is the same as what "seems" to be wrong to them - which perfectly illustrates the need for some data. Somebody has to do this test!

The simplest fact that I think we can all agree on, is that leaves are the solar panels that gather energy from light and convert that energy into food, which is then used to grow the body of the plant.

If you take the leaves off, you reduce the energy gathering capacity of the plant, and since you are on a limited time schedule, you don't have time to pause to recover, so you've limited the final size of the end product.

This defoliation myth requires us to believe that a SEVERELY defoliated, super stressed plant, can not only recover, but then come back and EXCEED what it would have done naturally without that stress. This is the part that defies physics.

You simply can't get something from nothing. If you manage to prove you've done it, I'll happily attend the awards ceremony where you get your Nobel Peace prize for disproving one of the most fundamental laws of the universe.

This issue perfectly represents the quandary of the current state of the Cannabis industry where the people that know the most about growing Cannabis and truly have the passion to stick with it, generally don't come from scientific backgrounds. They're great people, and many are brilliant at growing cannabis, but they never got that background education that makes a scientist agnostic about everything.
A scientist learns that you never believe - or disbelieve - until some logical information presents itself and provides a clear reason for leaning one way or the other.

Most cannabis farmers will certainly have spent some time studying their favorite plant, but how many actually sit down and truly study basic Biology, Chemistry or Physics textbooks? Missing out on that foundation creates big holes in the picture when you're trying to be a horticultural scientist - which you are if you're serious about grow pot.

Claiming the title "Master Grower" perfectly illustrates this issue. In the rest of the agricultural world, you can't just randomly bestow upon yourself the title "Master." Agronomy and Horticulture students spend years of dedicated study before a Masters Degree is bestowed upon them - by others. You can't just walk out from your first garage grow and claim that title for yourself. To be a Master actually means something. You get trained in Chemistry and Physics and Biology, and along the way you learn critical thinking, and the scientific method, and you understand the importance of performing studies that can be repeated and are published openly in Scientific Journals. In the cannabis world, that broad range of training is often missing.

We have a generation of highly skilled Cultivators with a lot of very real knowledge and experience, but without the science training they need to help them see through the mythology we get from other growers, and the outright deception we frequently get from product manufacturers.

We have to acknowledge where we come from. In the not-so-distant past, writing an article about growing was like printing your own ticket to prison, so it was hard to find information about growing cannabis. Someday those times may come to be called, "the dark ages of pot." If we want to really learn about our girls, we have to let go of those ways and rely on the scientific process enough to begin questioning all these myths that began in those times and are still being taught today as if they are fact. We have to learn to apply that scientific agnosticism and question everything that we think we know. Otherwise we'll just be stuck there in the dark.
Now that we can actually talk, and write openly... We have to learn to think like a scientist to get some real answers to the questions we've only guessed about in the past.

This issue of Defoliation, or Abscission Stress when it's done in flower, is only one of the many questions we have to answer. But as scientific experiments go, this is a super easy test to perform. It doesn't require a big budget or any technical tools to answer the question. All it takes is a little careful preparation to design a test.
Let's Do It!

I'm proposing that we (commercial growers), devise and perform, a real scientific test that can put this baby to bed once and for all, and make the results openly available to all growers.

I'm hoping that by openly designing and performing this test as a group, maybe a few Bro-Scientists will join in and begin to see the beauty of working and thinking about farming in a more scientific manner.
CAN YOU DO THIS TEST - AT YOUR FARM?

HERE'S THE QUESTION:

Does removing the leaves from a Cannabis plant, at different times in the flower cycle, have any impact on:

1. Dry usable "A" grade bud weight
2. The ratio of "A Bud" to "larfy bud"
3. THC, CBD and Terpene levels

TEST METHODS:


Using a single strain of plants at a time, in good health, started from evenly sized clones, grown under uniform feed/water/temp/humidity conditions, and NOT using the outside rows of the garden where light will be uneven.

• All plants undergo the same topping schedule to create an even and flat canopy.
• All groups undergo the same preventive IPM spray schedule.
• Plant clones into final pots or beds and begin defoliating 3 weeks later.
• Do NOT remove any leaf or bud due to discoloration, aging, Powdery mildew, Budrot, or other issues. (These conditions may be caused by defoliation)
• During each week of the entire veg and flower cycle, take one test group of plants and remove ALL leaves that measure greater than 2" across.
• Keep one bed untouched to act as the Control group.
• The total number of defoliated beds will depend on the ripening schedule of that particular strain, so if it is an 8 week strain you will have 7 test beds. A 12 week strain will have 11 test beds.
• ONLY the Control Bed will be used to determine maturity, measured as roughly 25% amber Trichomes. The actual harvest date is not critical as long as all beds are harvested on the same day, and ONLY the maturity of the control bed is used to determine harvest date.
• In order to properly account for the possibility of delayed onset of maturity caused by early defoliation, all beds must be harvested at the same time as the control bed - even if they are not fully matured at the same time.
• Test each group, for THC, CBD and Terpene content.
• After trimming all buds, the finished material is passed over a screen with openings of roughly 5/8" to 3/4" to searate the Top grade buds from the B grade and trim.
• Dry buds with visible Powdery Mildew or Budrot are weighed and separated. This group is listed as "discarded" to account for the possibility of defoliation causing an increase in the occurrence of fungal pathogens.
• This list is just a start. There are FAR more variables that need to be defined and controlled before you actually run the test - let's talk.

If you are the lead cultivator in a large farm with tightly controlled environmental conditions, perhaps you can volunteer to perform the test???

We need multiple farms to run the test with different strains each time.

We need to get results from at least two strains in each group of Sativa, Indica and Autoflower.

Any thoughts on how to design the test? I would be happy to work with you to create an outline for how the test is to be performed.

After a couple test runs are complete, I will put the results in a spreadsheet and make it available for everyone.

______________________________ ______________________________ ___________
My own predictions...

I'm not trying to promote more myth here but I do have a side prediction that I'll throw out because I think it might entice some of the more serious farmers into helping with this project. In a different study I found recently, cannabis plants were severely wilted (drought stressed) but only in week 7 and the results were STUNNING!

This study performed by Deron Caplan at the University of Guelph...

Upon harvest, drought-stressed plants had increased concentrations of major cannabinoids by 12% compared with the control.

Further, yield per unit growing area of THCA was 43% higher than the control, CBDA yield was 47% higher, THC yield was 50% higher, and CBD yield was 67% higher.

What would happen if you combined drought stress, with abscission stress in week 7?
We have Soooo many exciting questions to answer...

https://www.linkedin.com/pulse/defoliation-bro-science-myth-just-wont-die-glen-johnson/

 

[@hempy]

Give me a brake i have run so many grow threads from seed to finish threw the last decades i lost count.

In every grow thread i did i had up to dates information with pictures weekly if not twice a week and that included Defoliation of my plants.

Your arguing about a topic you clearly know very little about. Your reason is more about harassing me.

You posted this after a person who works in the cannabis industry posted with pictures showing how they defoliate massive Greenhouses full of plants to increase yield..

Originally posted by Chi13 View Post

Great post and I love your set up, and apologies for only quoting a bit of it, but didn't want to clog up the thread anymore. Very nice stepping in to help Hempy, but I think you misunderstand. Hempy makes claims from time to time that people disagree with. No one is crucifying him, just questioning some of his statements.

You then claim Science has no clue lol

Well, the science hasn't caught up. In fact defoliating may be a myth. Don't take my word for it, please look at the links I posted. I only brought it up because you advocated removing all fan leaves.

You are here to simply try and prove i am wrong because you have a hard on for me.

This clearly says older leaves Shade leaf dont contribute much to plant growth.

It is backed by scientific research that shows that older plant leaves do not contribute as much to plant growth as new, smaller leaves, but instead, they become detrimental.

This clearly says ethylene is found in higher concentrations in older leaves and ethylene is known to lower yields because of its ability to trigger the aging processes within plant cells.

Defoliation has been proven to boost the yields you can get from your cannabis garden. There are two angles to this: the first revolves around the plant hormone ethylene, which is known to lower yields because of its ability to trigger aging processes within plant cells.

Per nature’s design, ethylene is found in higher concentrations in older leaves and flowers, such as those at the lower ends of the cannabis plant. Defoliation effectively nips these leaves and flowers, triggering higher yields for the plant.

They defoliate Cotton and a lot more this is nothing new to Agriculture.

 

[Switcher56]

Can we agree to disagree... do whatever floats your boat (addressed in "general")

... in closing... my daddy is stronger than your daddy!

 

[TheDarkStorm]

Some of you might want to check out info on the jungle boys commercial grows......and I think they work with their method now because of doing large side by sides with clones....I think with their method the aim is to get the biggest largest flowering tops indoors rather than a nice looking plant with flowers and leaves.....I believe with their method the plants are completely stripped of everything but the very top tips before being put into bloom....so basically top one node is left and then flip..im sure there are pleanty of pictures of the results.

 

[@hempy]

Some of you might want to check out info on the jungle boys commercial grows......and I think they work with their method now because of doing large side by sides with clones....I think with their method the aim is to get the biggest largest flowering tops indoors rather than a nice looking plant with flowers and leaves.....I believe with their method the plants are completely stripped of everything but the very top tips before being put into bloom....so basically top one node is left and then flip..im sure there are pleanty of pictures of the results.

If you strip a plant of all its leaf and you only leave the nods the plant will stop growing and re focus all its energy back to growing leaf.

I know as i experimented long ago and took x number of plants to different stages of deflation to see what would happen.

 

[Hammerhead]

No one will change Hempys mind.

 

[Chi13]

Give me a brake i have run so many grow threads from seed to finish threw the last decades i lost count.

In every grow thread i did i had up to dates information with pictures weekly if not twice a week and that included Defoliation of my plants.

Your arguing about a topic you clearly know very little about. Your reason is more about harassing me.

You posted this after a person who works in the cannabis industry posted with pictures showing how they defoliate massive Greenhouses full of plants to increase yield..


You then claim Science has no clue lol



You are here to simply try and prove i am wrong because you have a hard on for me.

This clearly says older leaves Shade leaf dont contribute much to plant growth.


This clearly says ethylene is found in higher concentrations in older leaves and ethylene is known to lower yields because of its ability to trigger the aging processes within plant cells.



They defoliate Cotton and a lot more this is nothing new to Agriculture.

Lol, get over yourself. I am not here to try and prove you wrong. I don't give a fuck about you. You are obviously paranoid. I am only interested in the science around growing, not about propping up your delicate ego.

If you actually bothered to read my posts you would see that a few posts above is also by a commercial grower. Commercial growers all differ from each other in how they grow. I used to be a horticulturist and grew up in a family horticulture business (not cannabis related). If you read the links you would see that some crops respond to defoliation (like cotton), others do not.

Anyway it is pointless debating with you as you don't bother to give others the respect of even reading their links. Ironic as you always complain about others not respecting you. You also take disagreement as a personal insult where none was intended. Won't reply to any more of your posts.

 

[@hempy]

This is not a competition this is about science and facts.

I really dont care if you and hammer feel but hurt.

Trolling me and flaming threads to get at me dose not bring positivity to the forum or dose it help any one.

believe it or not people do defoliate their cannabis plants and that includes the Cannabis industry not just home growers and they do it because it works.

No ones telling any one to do it to their plants but dont tell me i am wrong when the yields i get alone shows it works.

This

Grows into this

If you think you can improve on this i am all ears but until then let it rest.

 

[Hammerhead]

Any topic that comes up and any disagrees with you, you take it as an attack. All I said was none can change your mind and your response is I'm butt hurt. In what reality does that make sense. As all can see its more than a few that think what you do is not the best method to grow cannabis. As you know I don't care how you grow. When others don't accept your nonsense you turn 10. Why do you care so much when any disagrees. Move on. Stop worrying about who is and isn't agreeing with you. You like to strip your plants of their leaves so do that .