To defoliate or not?

[Agronomist]

Current research shows the defoliation in Cannabis is a pretty bad idea.
You will get less inflorescence and a smaller amount of total THC per plant.

https://www.sciencedirect.com/science/article/abs/pii/S0926669021002922

 

[exploziv]

Current research shows the defoliation in Cannabis is a pretty bad idea.
You will get less inflorescence and a smaller amount of total THC per plant.

https://www.sciencedirect.com/scienc...26669021002922

Good find! Just looking at the pics and graphs tells me its a gem.
I just downloaded to have a read! If anyone needs it for free..
D.O.I. is:
https://doi.org/10.1016/j.indcrop.2021.113528
(copy the above, paste it into scihub to download)
scihub.se that is.

Later.edit:
Btw, conclusion is defoliation as a means to increase yeld is strain dependant.
In this study, Himalaya is sativa dominant, while Fuji is indica dominant. 85% of leaves were defoliated, leaving just the top ones.
The graphs that matter:

 

[@hempy]

I need a refresher on nutrient sinks in older leaves. (I'm in the non-defol. camp.) The only reason I take leaves off is dying/yellowing, or to prevent some moisture from overlap. I've heard it suggested though, that at a certain stage of development, older leaves just become a sink and nutrition goes in but doesn't really come out. Is there any reason to think that a removal of older leaves to alleviate that possibility is worth anything?

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]

Air & Light On Leaf Photosynthesis:

As a leaf ages, its ability to photosynthesize follows almost like a bell curve, with a peak around 20-60 days. Here it can be seen how leaf age is very impacting on its photosynthetic capacity. As the leaf gets older, aging or senescence brings about deactivation of enzymes and degeneration of chlorophyll. This is why older leaves start dying and fall off on the lower end of the plant.

It has been suggested that older leaves may act like sinks when they can no longer continue to efficiently convert light into food. But this is not what happens. In the early stages of leaf development, leaves act like sinks. In just a few days, leaves begin the Sink To Source transition where they start supporting themselves and begin exporting photosynthetic resources, as a source. Its at this point and for the remainder of its life until cessation that it stays as a source. Removing leaves does not provide more photosynthate for flowers, as leaves are providing energy, not requiring it. They are sources. The plant also utilizes the nutrients and energy leftover from the leaf, prior to abscission during senescence. This is what happens during the late stages of flowering when the plant is searching for nutrients.
https://www.cocoforcannabis.com/community/photons_corner/to-defoliate-or-not-to-defoliate/

 

[Chi13]

To Defoliate Or Not To Defoliate (full article)

Dr. Photon’s Corner



The issue of leaf removal for cannabis through the process of defoliation has troubled growers for a long time and will probably continue to do so regardless of any evidence. Here i will be discussing what defoliating is, the most popular theories and the science of each.

Every method that removes material from a plant is a form of pruning, which is to control the shape, structure and function of a plant and improve its overall health, performance or appearance.

Defoliation describes the process of removal or loss of leaves. It does not detail the methods or purposes it may be used for. That requires extended terminology whether that is current or new. The method of defoliating in agriculture is not a practice used for improving product yield, but for other practical purposes such as harvesting efficiency, forced dormancy, disease control etc. Cannabis horticulture is the only field where defoliating is used to try improve yield. Its probably not known where it started but cannabis growers are always trying to find ways of improving their grow and as such will inevitably be a target for unproven practices. There are various methods on how defoliation is recommended to be performed, but typically it will involve the selective or non selective removal of leaves, of a varying amount at varying times during a plants grow. This is dependent on the method provided by the grower and their reasons or beleifs which define the process.

Air & Light On Leaf Photosynthesis:

As a leaf ages, its ability to photosynthesize follows almost like a bell curve, with a peak around 20-60 days. Here it can be seen how leaf age is very impacting on its photosynthetic capacity. As the leaf gets older, aging or senescence brings about deactivation of enzymes and degeneration of chlorophyll. This is why older leaves start dying and fall off on the lower end of the plant.

It has been suggested that older leaves may act like sinks when they can no longer continue to efficiently convert light into food. But this is not what happens. In the early stages of leaf development, leaves act like sinks. In just a few days, leaves begin the Sink To Source transition where they start supporting themselves and begin exporting photosynthetic resources, as a source. Its at this point and for the remainder of its life until cessation that it stays as a source. Removing leaves does not provide more photosynthate for flowers, as leaves are providing energy, not requiring it. They are sources. The plant also utilizes the nutrients and energy leftover from the leaf, prior to abscission during senescence. This is what happens during the late stages of flowering when the plant is searching for nutrients.

One could argue that reducing foliage will help prevent leaves from the top, from blocking light and reaching lower into the canopy, however this is only going to end up with the same 'total' photosynthetic yield. All that is changed is where the photons will land. Any light which is not absorbed from higher leaves will pass through to lower leaves. This is called the transmittance effect. The idea that top leaves block lower leaves and waste usable energy, is incorrect for this very reason. As light is captured efficiently. Infact exposing shade leaves could be harmful because of the shade vs sun leaves problem. Shade leaves have a different anatomical structure compared to sun leaves, as such its capacity to process light is limited and is negatively affected through factors such as photoprotection and photoinhibition. It takes time for leaves to adapt to new lighting environments. Removing sun leaves and exposing shade leaves, could slow growth and add time to the overall schedule. This is the reason why plants have problems when being introduced into new lighting environments.

With airflow and transpiration, the process is completely passive. But we can prevent problems such as water vapor barriers from static air, sufficiently with active air movement. By removing leaves, you ultimately limit the plants ability to move water and nutrients through transpiration, as the leaves that are removed contribute to this through stomatal movement. By removing leaves you prevent the plant from breathing so to speak, as such the plant tries to recover and attempts to generate more leaves as a result.

Floral Morphogenesis:

It has been suggested that a flowers interaction with light and wind could cause such reactions that enables the flower of cannabis to develop, bulk or swell more as a result.

Morphogenesis is the biological process that causes an organism to develop its shape. A plants morphological response to environmental factors has been studied for several decades. Examples of environmental stimulus are light, air, wind, temperature, touch, damage etc. Although we may not fully understand the physiology or biochemistry of plant sensory chemicals. We do however understand the fundamentals of their functions, which have been wonderfully displayed through many experiments over the decades. Its through the hard work of plant science that we can understand these processes and use them to our advantage.

Plants not only use light for photosynthesis, but also for mediated responses where light is used as signals or information to generate growth patterns determined by specific wavelengths of light. These are mediated by photoreceptor proteins such as phytochromes, cryprochromes, phototropins. I like to think of it as photosynthesis manufactures energy, where as morphogenesis says what is done with some of that energy. Examples of photomorphogenesis are photoperiodism, phototropism, shade leaf avoidance, stem elongation, chloroplast movement, stomatal opening.

Plant science has not observed any photoreceptor proteins in flowers, or that there are any properties of flower morphology to light. Phototropism for example has been shown to only be found or function in the apical meristem of plants. Photoreceptors responsible for photoperiodism are only found in leaves, as such exposing light to other parts of plants has no effect on flowering.

Its also been showed that light itself has very little impact on the characteristics of flower development, suggesting that during flowering. Light factors such as different wavelengths, has very little to no impact on floral morphology.

Hans Mohr 2012 · Science of photomorphogensis:

"The characteristics of the flowers (including stamens, pistils, corolla and calyx) are hardly modified by light. A potato plant will form very similar flowers under all circumstances which allow flower formation at all."

Thigmomorphogenesis is the morphological response by plants to mechanical sensation. Examples of this are plants response to wind. Outdoors where wind sways branches, this creates chemical messages that tells the plant to strengthen stems and leaves. This is observed well with greenhouse plants where air movement is minimal. Branches are spindley and weak with leaves having very thin cuticle layers.

There has been no evidence or indication of floral morphology from mechanical stimulation such as wind or airflow. As such it is hard to conceive the idea that defoliating improves growth through thigmomorphogensis.

Stress & Phloem Translocation:

Studies on defoliation have showed that a majority of species of plants, show an ability or buffer to compensate for some type of structural damage during its life. Its almost expected by plants that some event will happen and that it be prepared. What defoliation studies have in common, is that plants are not negatively impacted by the loss of leaves up to a certain point (around 25%). It seems that a plant will typically have more leaves than it requires, almost as if history has taught it to anticipate the loss of leaves through enviromental factors. This was some of the conclusions by people conducting these studies.

Now a plant holds the ability to store nutrients (photosynthate) in its roots, branches, leaves and fruit. This is its major storage sink during growth and vegetation. However in the event of stress, injury or sickness, a plant may be able to redirect this stored energy through a process called phloem translocation. Some plants have enough stored resources that they can revegetate, if all their top growth is removed. Cannabis does not hold this ability but it may be possible that all plants have some degree of stored energy to respond to stressful events. In the partial defoliation studies, some report the event where the variables grew taller than the controls. Suggesting that the plants response to reduced leaf numbers, caused them to branch out to create new leaves to sustain its level of photosynthetic capacity. This response could be aided by stored resources through phloem translocation. This also brings up the interesting reason of why supercropping (i like to call it scropping) may appear to increase growth and vigor.

However, to all extent there has been no evidence to support this. The problem here is that any resources that is moved because of a stress response, is prioritizing it for the repair of damage or the development of new leaves. This has been observed by many, as a delay in flowering due to the stress induced by defoliation.

Evidence And Conclusion:

I looked all over for any and all controlled grows, comparing defoliated plants to controls. Unfortunately i found very few. The ones i did find showed clear indications of no improvement but infact a decline in yeild. You would think that of all the people who have grown, they would have done such a simple experiment. However it seems people keep insisting on doing the method without controls and make subjective opinions on the matter. The most surprising one is where people defoliate and somehow are surprised that a few days later there is more growth. Then conclude the success of their experiment. I cannot enough make it clear how important, controlled side by side comparisons are. This is to remove any and all variables that you 'may' or 'may not' expect, regardless of what you have experienced in the past. Visial bias alone is enough to convince somone of something that is not true. Not everything is as it appears.

I have been through many forums and threads where people claim once and for all to answer this issue and would conduct a controlled grow. Only to almost always fall through and never return, countless threads encouraging people to post their results. Nothing!, ever at all comes to light. Only the select few that seriously go through with it, end up showing the failure of defoliation. Most who are educated in botany or horticulture almost always seem to disagree with the method. Field experts in commercial grows do not employ techniques even though there are ways of doing it efficiently. Studies find no connection, no evidence of any kind.

Although i support the idea of providing more light to the lower canopy, this is just for quality rather than quantitiy reasons. Whether this is by removing a select few fan leaves, or by training or pruning the plant to allow more light to get through.

If anyone has any other possible theorys or further information on the subject that may be interesting, please let me know. If there is anything that may show otherwise i am happy to know, however as it stands i am unconvinced. I would love the idea, of the practice of defoliation to increase yields. Another technique for improved yields is always wanted. However i need more than empiricle data. Even if there is no sound science of the reason how it could possibly work, i would need at least some evidence of a control compared to a variable.

The following are testemonies from several published and qualified cannabis botanists and horticulturists. If you trust some of the best botanists/horticulturists in cannabis, follow their work, read their books. Then at least trust them when they also say that traditional defoliation has no bearing on improved plant performance. What does help and is commonly accepted is the traditional work of pruning in horticulture. Controlling the shape, structure and function of a plant and improve its overall health, performance or appearance.

#LEAVE THE LEAVES

Leafing By Cannabis Botanist, R.C. Clark:
Leafing is one of the most misunderstood techniques of drug Cannabis cultivation. In the mind of the cultivator, several reasons exist for removing leaves. Many feel that large shade leaves draw energy from the flowering plant, and therefore the flowering clusters will be smaller. It is felt that by removing the leaves, surplus energy will be available, and large floral clusters will be formed. Also, some feel that inhibitors of flowering, synthesized in the leaves during the long non inductive days of summer, may be stored in the older leaves that were formed during the non inductive photoperiod. Possibly, if these inhibitor-laden leaves are removed, the plant will proceed to flower, and maturation will be accelerated. Large leaves shade the inner portions of the plant, and small atrophied floral clusters may begin to develop if they receive more light. In actuality, few if any of the theories behind leafing give any indication of validity. Indeed, leafing possibly serves to defeat its original purpose. Large leaves have a definite function in the growth and development of Cannabis. Large leaves serve as photosynthetic factories for the production of sugars and other necessary growth sub stances. They also create shade, but at the same time they are collecting valuable solar energy and producing foods that will be used during the floral development of the plant. Premature removal of leaves may cause stunting, because the potential for photosynthesis is reduced. As these leaves age and lose their ability to carry on photo synthesis they turn chlorotie (yellow) and fall to the ground. In humid areas care is taken to remove the yellow or brown leaves, because they might invite attack by fungus. During chlorosis the plant breaks down substances, such as chlorophylls, and translocates the molecular components to a new growing part of the plant, such as the flowers. Most Cannabis plants begin to lose their larger leaves when they enter the flowering stage, and this trend continues until senescence. It is more efficient for the plant to reuse the energy and various molecular components of existing chlorophyll than to synthesize new chlorophyll at the time of flowering. During flowering this energy is needed to form floral clusters and ripen seeds. Removing large amounts of leaves may interfere with the metabolic balance of the plant. If this metabolic change occurs too late in the season it could interfere with floral development and delay maturation. If any floral inhibitors are removed, the intended effect of accelerating flowering will probably be counteracted by metabolic upset in the plant. Removal of shade leaves does facilitate more light reaching the center of the plant, but if there is not enough food energy produced in the leaves, the small internal floral clusters will probably not grow any larger. Leaf removal may also cause sex reversal resulting from a metabolic change. If leaves must be removed, the petiole is cut so that at least an inch remains attached to the stalk. Weaknesses in the limb axis at the node result if the leaves are pulled off at the abscission layer while they are still green. Care is taken to see that the shriveling petiole does not invite fungus attack. It should be remembered that, regardless of strain or environmental conditions, the plant strives to reproduce, and reproduction is favored by early maturation. This produces a situation where plants are trying to mature and reproduce as fast as possible. Although the purpose of leafing is to speed maturation, disturbing the natural progressive growth of a plant probably interferes with its rapid development. Cannabis grows largest when provided with plentiful nutrients, sunlight, and water and left alone to grow and mature naturally. It must be remembered that any alteration of the natural life cycle of Cannabis will affect productivity. Imaginative combinations and adaptations of propagation techniques exist, based on specific situations of cultivation. Logical choices are made to direct the natural growth cycle of Cannabis to favor the timely maturation of those products sought by the cultivator, without sacrificing seed or clone production.

Pruning By Ed Rosenthal:
Indoors, the canopy absorbs virtually all the light, leaving little in the shadows below. For this reason, the understory below the canopy contributes little energy to the plant. Instead, it costs the plant nutrients, increases humidity, and stops air-flow.

Pruning the lower limbs creates more air-flow under the plants and creates cuttings for cloning. It also forces the plants growth to the top limbs that get the most light, maximizing yield. These lower leaves and branches should be removed to create and open airspace.



Pruning By Mel Frank:
Under sunlight, you can expect to harvest a plant with strong colas on every branch, rather than one large top cola and much smaller branch, if you clip the top growing shoot about two weeks before flowering. Under weaker electric light, removing the top shoot may result in smaller buds and possibly a smaller harvest. Don't use late pruning as a general procedure under artificial lights, except as a last resort when one or two plants are outgrowing the rest of the crop. These fast-growing plants prevent the light from being positioned closer to all the plant tops. Bending and training these tallest plants is the best procedure. When the plants first start to flower, clip off the lowest, under-developed branches. These branches won't be worthwhile buds anyway, and by removing them, the stem and root system feed only the strong branches, which consequently yield larger buds. Removing lower branches also allows reflected light to better illuminate the whole plant and promotes better air circulation.
Once the buds begin to form, remove some of the large fan leaves along the main stem. This allows the light to reach the lower buds and they'll develop more 'fully'. Don't over do it; once a leaf forms it produces more "growth energy" for the rest of the plant. If you strip a plant of its leaves, your lessening its capacity for growth. Removing most of the health leaves also can delay flowering. In an outdoor plot, plants stripped of leaves flowered two weeks later than their sisters that were left intact. Under lights, remove only some upper main stem fan leaves that shade lower branches.

Jorge Cervantes On Leaf Removal:

I am not a huge fan of jorge but i do like his character and so added a video of his thoughts on defoliation.

As always please comment your thoughts or any questions on the subject.
https://www.cocoforcannabis.com/community/photons_corner/to-defoliate-or-not-to-defoliate/

 

[Chi13]

An actual small defoliation experiment showing decreased yield from defoliatin;

Why Not To Defoliate Removing Fan Leaves. Comparison.

ok quite simple really do not remove fan leaves because you read somewhere that it makes buds bigger, its a load of bollocks because I tried it and below is the proof.

both plants grow side by side fed exactly the same with same environment etc, not one single difference except I removed ones leaves and left the other on.

Top plant (defoliated) in pic is has much smaller less compact buds that the bottom one.

Just thought I owuld put this up after a suggestion from jimmi420 ( thanks Jimmi) for new growers so they do not make the same mistake as me.

I am glad I done it because I was able to see for myself but I am a bit pissed I have lost a considerable amount of weight due to not taking more experienced growers advice.

DO NOT TAKE OFF YOUR FAN LEAVES OFF YOU WILL STUNT THE SHIT OUT OF YOUR BUDS.
https://www.thctalk.com/cannabis-fo...t-To-Defoliate-Removing-Fan-Leaves-Comparison​

 

[@hempy]

Why do they prunes fruit trees ?

 

[Donald Mallard]

Why do they prunes fruit trees ?

firstly ,
fruit trees are perennials , and not in the same group of plants as cannabis ,
they are perennials vs annuals

secondly , they are pruned , but not defoliated ,
there is quite a difference ,
many folks do some pruning to their cannabis plants ,
as mentioned i do it also , for reasons i have already outlined in a few posts ,

here are a few reasons to "prune" , not "defoliate" fruit trees since that is the question ,


Fruit trees should be pruned for several reasons:

• To develop desired tree shape;
• To maintain the tree at the desired size;
• To allow sunlight and spray materials to enter the center of the tree;
• To improve tree strength and encourage new shoots;
• To improve air circulation within the tree and reduce the potential for disease; and
• To remove dead or broken branches.

 

[Chi13]

Why do they prunes fruit trees ?

Lots of reasons, and none of them have anything to do with defoliating cannabis.

What fruit growers don't do is defoliate their fruit trees. They cut off old and weak branches and some growing shoots. I cut off the odd lower branches in my cannabis plants too, but I don't rip off all their leaves.

Edit, Donald beat me to it.

 

[@hempy]

Defoliation is technically a type of pruning, except it specifically refers to removing of leaves, generally fan leaves, with the intention of allowing more light and air flow around and through the plant.

Why do we prune fruit trees ?

The most basic concept of pruning is that by cutting it back it will promote new growth, and that's a good thing because it encourages more fruit production. Fruit trees that are left to their own devices, without pruning, tend to become hard stemmed. This restricts new growth, which ultimately restricts fruit growth.


Do some research on hormone ethylene.

 

[Chi13]

Defoliation is technically a type of pruning, except it specifically refers to removing of leaves, generally fan leaves, with the intention of allowing more light and air flow around and through the plant.

Why do we prune fruit trees ?

The most basic concept of pruning is that by cutting it back it will promote new growth, and that's a good thing because it encourages more fruit production. Fruit trees that are left to their own devices, without pruning, tend to become hard stemmed. This restricts new growth, which ultimately restricts fruit growth.


Do some research on hormone ethylene.

You are just arguing for the sake of arguing. This is just ridiculous. Of course a tree that's alive for several years will become hard stemmed. Cannabis is an annual, and completely different. Again, you do not defoliate fruit trees. Pruning is done roughly every year. Cannabis only lives for a year.

 

[@hempy]

You are just arguing for the sake of arguing. This is just ridiculous. Of course a tree that's alive for several years will become hard stemmed. Cannabis is an annual, and completely different. Again, you do not defoliate fruit trees. Pruning is done roughly every year. Cannabis only lives for a year.

No arguing from my side you mite be.

I am giving you scientific facts that you and a few others just over look and ignore because it dose not sit with your opinion of things.

Pruning like it or not is a form of Defoliation.

Why do un pruned fruit trees become hard stemmed and as a result restricts new growth, which ultimately restricts fruit growth ?.

Do you think it may have something to do with the plant hormone ethylene ?.

What is 100% fact LIKE IT OR NOT old cannabis leaf SHADE LEAF ends up being more a problem for the plant than a valued asset.

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.

I ran side by side plants and experimented. I know how far a plant can be defoliated all the way until harvest.I do it and not once have i attacked people that dont defoliate their plants.

But here we have people that have never tried it that have no clear understanding of the science telling people like me who do it we are wrong.

Your argument is based on selective papers that have nothing to do with cannabis. Yet i can find you lots of research that shows and supports defoliation on Tomatoes and other crops that improved yield not hurt it.

Research papers can be used to preference a particular point of view and are subject to the research methodology that is used.

Like it or not industry is doing it and so are home growers choice is yours.

Just dont tell me i am wrong because you dont agree.

 

[Chi13]

No arguing from my side you mite be.

I am giving you scientific facts that you and a few others just over look and ignore because it dose not sit with your opinion of things.

Pruning like it or not is a form of Defoliation.

Why do un pruned fruit trees become hard stemmed and as a result restricts new growth, which ultimately restricts fruit growth ?.

Do you think it may have something to do with the plant hormone ethylene ?.

What is 100% fact LIKE IT OR NOT old cannabis leaf SHADE LEAF ends up being more a problem for the plant than a valued asset.


I ran side by side plants and experimented. I know how far a plant can be defoliated all the way until harvest.I do it and not once have i attacked people that dont defoliate their plants.

But here we have people that have never tried it that have no clear understanding of the science telling people like me who do it we are wrong.

Your argument is based on selective papers that have nothing to do with cannabis. Yet i can find you lots of research that shows and supports defoliation on Tomatoes and other crops that improved yield not hurt it.

Research papers can be used to preference a particular point of view and are subject to the research methodology that is used.

Like it or not industry is doing it and so are home growers choice is yours.

Just dont tell me i am wrong because you dont agree.

I have answered all this in my previous posts. Either you aren't reading them or you do not understand.

Pruning fruit trees and defoliating cannabis have zero in common. I could not think of a worse plant comparison if I tried.

You have presented evidence from sunflowers, cotton, and now fruit trees, yet you accuse me of presenting papers that "have nothing to do with cannabis"? You are kidding,
Not only that but you have been quoting without referencing. The internet is full of people saying that defoliation works on cannabis, but no one has the evidence to back it up, which is pretty much what I have been arguing.

Funny, you suddenly claim to have done side by side experiments after this has been requested this entire thread, and in the haze thread. Show us the results. Photo's perhaps? I call BS.

Some of the industry is practicing this. Others are not. Either way unless there is a proper experiment done and repeated, we won't know for sure if it works.

 

[Donald Mallard]

when someone prunes their fruit trees ,
they never say they defoliated it ,
those two things are not the same at all ,
maybe denuding could be seen as a synonym to defoliation,,
but pruning and defoliation are not the same ,
and its splitting straws trying to say they are ....
perhaps it could be seen as a radical form of pruning,
because thats what it is ....



scientific facts will be in the form presented by agronomist on the previous page,
where we see a link to the study and how it was done, who by etc ,
not just a quote that could be from any old tom dick or harry ,
please include proper links to support your "facts" or they are just something anyone can trot out ....

i doubt too many large scale growers are doing defoliation ,
its quite laborious and unneccesary in most cases ,
i did note maryjanes post on it,
and will say that since those plants are stacked so close pruning the under parts of the plants to allow airflow was probably necessary,
though there is/was no need to prune off all the leaf from the plants ,
there is never a need to do that ,
it will shock the plants , i am 100% sure of that ,
as a result there will be other detrimental side affects ,
those have been touched on by the study agronomist posted ,
and other links chi has provided ..

im gonna add a few pictures to show how i prune when there is just too much mass ,
and or the plants are too close and need a way to allow a bit more air ,
two pictures , clearly showing the underneath cleared out , and some in the centre ,
but no defoliation ...
btw , i did try taking off the bulk of the leaf from my plants when i was younger,
i saw the negative side to it and stopped pretty quickly ,
so yes i have tried it and found it to be ineffective and detrimental ..

 

[f-e]

I'm aggressive with larger plants, to slow them on purpose. It may not help that plants performance, but helps others sharing a scrog net. A paper saying aggressive slows a plant, doesn't say it's a bad thing to me. Maybe for that plant under testing it was, but for me that's a helpful response to know about.


I don't have a side by side. I never can. I do them, but the results of just one are no use. I must do them again, swapping sides. In a room that's done enough previous grows to use them as the control. This isn't possible to show in a single story. When I do see a side by side, I don't see it as the truth until it's been done the other way around. Many of the tests we see published are later pulled apart by another set of eyes. I'm really not looking for somebody to do a single side by side. I'm not looking for anybody to show me anything. Though I will look and wonder what they got wrong. Like the above, where they found it bad, but then we see they took 85% away. Fooking ouch. It's no more than a third.

 

[exploziv]

Actually, that paper says it was bad for the indica dominant strain in the test and marginally better for the sativa dominant.
I can only take that as strain dependent, tho. Its too close to call it an improvement, even in the sativa leaning variety. But it does shows that sometimes it can lead to higher yeld. Marginally..

 

[Switcher56]

Some say tomatoes while others say to mah toes

 

[Hammerhead]

I would think any tests would need to do more than 1x to rule out any plant behaviour differences. When I grow the same plant it can do better/worse than the previous run even when all things are the same.. The data has to be reproducible.

 

[exploziv]

Ofc, but a 50 plants of each variety test in a controled environment in a medical cannabis facility gotta be better than nothing, and especially better than just some opinions on the internet.
Problem is, since it shows it's really strain dependent, makes it hard for the little guy to judge anything before he does some tests with the varieties he plans to grow. Also, I think reading that paper would help most growers when planning for a controlled side by side of their own, if they feel like going for that.

 

[NIKT]

I don't know if it's useful or not. old post from which forum. If not IC then ?? Too long ago to be sure. ?? more than 10 years ago. LAI and K.

Associated with defoliation.

I've always liked what KNNA wrote. I kept it, it seems to me that it is from the times when LED panels were built in the so-called knna style with kapton and home-made aluminum mcpcb. Power diodes of that time had large housings, the little smd ones appeared some time later. Dragon series osram ??

Posted by KNNA

=========================================================================================================================================
knna napisał:

Thanks, guys. I hope we can work improving our setups by eliminating the wrong concepts that lead us to work on wrong directions.

In this sense, lets examine Penetration (BTW, if you want to find thousands of excelent botanists articles about this topic, search for "extinction coefficient k" (add "canopy" to eliminate results of other areas apart of botany).

The main thing I would like to dispell about Penetration is that the light source caracteristics, although affect on some degree, dont rule out it, but is one of the factors that affect less penetration. At least, if we consider just top lighting.

Penetration is mainly ruled out by how crowded is the grow area (how many leaves) and the angle of leaves. Light density achieved at bottom areas mainly depends of them, and just minimally of the caracteristics of the lighting, especially if its a fixed one.

Some botanist concepts are usefull in this context. Leaf Area Index (LAI) is an adimensional figure that informs of how many leaves there are for surface unit area. It sums the area of upper part of all leaves and divide it by the surface area of the grow. Thus a LAI=1 means that on a 1 sq meter of grow area, there is 1 sq meter of leaves (counting only upper part).

In general LAI is over 1, mostly between 2-4, but it may reach 6. Notice that growing techniques often are intended to strongly affect this parameter, thus the impact of SOG, SCROG, LST, defoliating, etc on "penetration".

Extinction coefficient (k) describes the attenuation of light density with vertical height. It depends strongly on the orientation of leaves. Planophile plants (most leaves are horizontal) have way lower K than erectophile plants (most leaves vertical). Especially when incident light comes from the zenit (the vertical).

The higher the LAI and k, the less light that reach the bottom areas.

In general, when using indoor just top lighting, it dont worth to have a LAI over 3. Usually a little over 2 is the max optimally useable indoors.

An ideal lighting must be designed according to LAI and k of plants being grown. And given the lighting setup is done, we must adapt LAI and k to the best values to get the best of the grow. Tyeing and pruning are great tools that allows us to strongly affect those parameters. Of course, LAI itself is very affected by how large is the plant, thus choosing the right vegetative time is critical to obtain the best results, as any mynimally experienced grower knows.

Therefore, its very difficult to generalize. What is good for 5ft plants probably isnt for 1ft ones. Different strains have different leaf angles, and more yet, plants have some ability to adapt it to the lighting environment. At the end, growers sharing their experience on their own conditions is the only key to improve on the long term.

There is no rules valid for all situations in this sense. Possible combinations of LAI and K are too many to fit a solution optimal for all. Aditionally, we can strongly affect them using growing techniques. Recently many people has discovered how defoliating plants may improve yields.

So we should forget to find an universal valid solution, but concentrate on understanding factors that affect on each situation and try to get the best for that concrete situation, either by manipulating the light setup, either by using general growing techniques.

But the main thing we must have in mind is that is not lighting that rules penetration, but plant's caracteristics.

Only understanding the given plant caracteristics we can design a lighting that works better for them. And on a opposite way, we can train our plants to use better a given lighting setup. Improvements on LED growing involve those two factors. Lighting and plants pattern must be considered together.
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