# The Numerous Benefits of ‘Selective Defoliation’ and Why I Trim



## cannetix Inc (Oct 25, 2017)

*The Numerous Benefits of ‘Selective Defoliation’ and Why I Trim*



*Disclaimer: I understand that this topic is controversial and that many threads on the topic already exist. This thread is intended only to provide my own personal view on the topic based on my own, personal research and experience.*
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‘Selective defoliation’, or as some growers refer to it in the cannabis community; Lollipopping is a topic that sees a great deal of debate. While many experienced growers swear by the technique, many others are adamant that it should never be done. To understand why selective defoliation, *when done properly*, can improve health, vigor, yield, etc. you must first understand some basics about plant physiology. Plants are autotrophs that synthesize their own food through photosynthesis, a process that occurs predominantly in the leaves. Cells high photosynthetic pigments – chlorophylls – absorb light and catalyze (“initiate”) a reaction between Water (H2O) and Carbon Dioxide (CO2). The result of this reaction is the simple carbohydrate or monosaccharide known as Glucose. Plants can then either use Glucose in the process of cellular respiration, burning it with oxygen to create energy. Alternatively, plants can use these monosaccharides as building blocks for more complex polysaccharides, such as Cellulose, that make up their structure and tissues.
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Although the entire plant appears uniformly green, it is important to realize that *only some* cells actually contain Chloroplast (The chlorophyll-containing organelles). If you look at plant tissue under a microscope, the majority of its cells will actually appear nearly completely colorless and translucent, with pockets of vibrant green appearing (mostly) surrounding pores on the leaves, known as Stomata. The argument against selective defoliation is a simple one; *the leaves are the “powerhouse” of the plant and for every leave that is removed the plants' growth will be stunted.*

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This, however, may not be entirely true. As leaves age, the density of chloroplast containing cells decreases significantly, as does the concentration of various phenols (Apigenin, Resveratrol, etc.). Due to the fact that a plant can only synthesize so many molecules of chlorophyll, and so many of these important phenols, *selectively* removing old-growth can, both in theory and as demonstrated by real-world study, *improve the photosynthetic properties of the remaining, young growth*. We see this same phenomenon occurring on a larger scale in forest ecosystems, where the clearing of old-growth trees causes undergrowth to flourish. Young undergrowth, which grows quickly, actually sequesters significantly higher levels of Carbon compared to massive old growth trees, many of which are done growing and have begun the slow process of rotting out from the inside. The following is an excerpt from a study done in '_Frontiers of Plant Science_', a rigorously peer-reviewed journal that is the #1 most cited and the leader in the field of agricultural sciences. The journal is available here.


_"In many plant species, *partial defoliation leads to increased photosynthetic rate in the remaining plant tissues* (Strauss and Agrawal, 1999; Retuerto et al., 2004), suggesting that compensatory photosynthesis is a common physiological response to leaf damage (Tiffin, 2000). However, increased photosynthetic activity is not a universal response to herbivory and does not always drive compensatory growth, possibly due to resource diversion into resistance traits (Tiffin, 2000). Herbivore identity can determine whether changes in photosynthetic rate and growth occur: for example, compensatory photosynthesis is induced by several insect herbivores of soybean and drybean, but not by Mexican bean beetle (Peterson et al., 1998). By contrast, aphid feeding on the perennial crop red raspberry frequently stimulates plant growth and influences nitrogen physiology (Johnson et al., 2012), which could reflect tolerance to aphid herbivory through increased plant vigor (Karley et al., 2016). Similarly in sugarcane, clonal variation in tolerance to root-feeding whitegrub correlated with increased plant vigor (Allsop and Cox, 2002). Plant vigor can provide tolerance to herbivory in a range of plant species (Price, 1991); higher abundance and fitness of many insect herbivore groups on vigorous host plants (Cornelissen et al., 2008) could reflect increased ability of vigorous plants to tolerate attack. Although plant vigor is likely to be controlled by multiple loci, quantitative trait loci (QTL) studies have identified genetic markers for vigor (e.g., root and shoot vigor in raspberry: Graham et al., 2011, 2014) that could be deployed in crop breeding.”_






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## cannetix Inc (Oct 25, 2017)

*Plant Hormones*


Another aspect of defoliation and how it may affect plant growth is through modifying how the plant produces various plant-growth regulators including Auxins, Cytokinins, and the hypothetical Florigens.All parts of the plant, including the leaves, produce these compounds and/or are involved in their metabolism so, in theory, by selective defoliation we can increase or decrease the level of certain growth regulating compounds. It is well known, especially amongst Cannabis growers that the Apical bud or “crown” produces high quantities of Auxins which inhibit lateral bud growth. By removing the apical bud, sometimes referred to as the “auxiliary bud” through “topping” we can significantly reduce native auxin production and increase lateral dominance. *How might removing leaves have similar effects?* One way may be through reducing the production of a hormone called *Ethylene*. Ethylene is a plant hormone produced at various stages of plant growth with complex effects, however, it is produced in the highest quantities in aging leaves and flowers. High quantities of Ethylene production in higher plants is directly related to yield reductions due to its ability to stimulate natural “aging” processes that occur within cells, also called senescence (https://en.wikipedia.org/wiki/Senescence). Ethylene also stimulates the ripening process and therefore increases the rate at which starch within the plant breaks down and reduces total time to harvest. It is quite widely known in the field of agricultural sciences that delaying ripening can increase yields by as much as 20%. While this is commonly achieved in research and in practice with Ethylene inhibitors, selective defoliation may also have similar effects. Another effect of Ethylene appears to be the inhibition of Auxin transport in plant tissue. Auxins are generally seen as “*growth stimulants*” and are found in highest concentrations in actively growing regions of the plant including the root tips, leaf apex (tip) and *flowers.* 





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## cannetix Inc (Oct 25, 2017)

*Mold, Mildew & Other Pests*​


One of the more well-recognized benefits of defoliation, of course, is its ability to increase light absorption and increase airflow, two things which *greatly reduce the likelihood of mold*, mildew, bud rot and other fungal infections. Similarly to the effects defoliation has on chlorophyll and photosynthesis, by increasing the concentration of phenols such as Apigenin and Resveratrol present in the leaves, we can also, in theory, reduce the likelihood of pests attacking plants by stimulating their natural immune activity. The following is an excerpt from US patent #US5848492A available here.

_“Selective defoliation of a field growing crop such as grape vines has long been known as a desirable practice. Thus, for example, U.S. Pat. 2,865,135, issued Dec. 23, 1958, inventors Gamboni et al. discloses a grape leaf stripping mechanism to strip the leaves from grapevines by a mechanical apparatus rather than manual defoliation. The apparatus disclosed in this patent uses a pair of beaters to effect the defoliation._

_More recently, the University of California publication on Grape Pest Management (2nd Edition, 1992, publication 3343) notes that among the practices for disease control are the removal of basal leaves from vines approximately two weeks after bloom. This practice reduces Botrytis bunch rot and produces a superior wine grape in many North Coast vineyards, and has also been reported to reduce first-generation leaf hoppers. The publication notes that most leaf removal is presently done by hand, but that mechanical systems are being developed and used by several growers. (Supra, xi.)_

_Removal of basal leaves on grape vines also permits the grape clusters to hang free and allows light penetration for coloring and budwood development, and allows air and chemical spray penetration for reducing molds, moisture, and insect infestation. Leaf removal has proven to produce a better acid/sugar ratio in ripening berries, and thus results in better quality wines and/or juices.”_

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## cannetix Inc (Oct 25, 2017)

*Carbohydrate Reserves, Nitrate reserves & Flavour*


There is also some evidence that selective defoliation can improve the quality and flavor of the finished product through a variety of means. First and foremost, by limiting the ability of the plant to photosynthesize in later stages of growth, we can force it to deplete Carbohydrate reserves which, in theory, means flowers with a lower sugar content. Due to the fact that sugars, under normal circumstances, *do not combust completely*, they can contribute to undesirable flavor and “harsh”, acidic smoke. The combustion equation for sugars is actually quite complex, resulting in the formation of aldehydes, ketones, carboxylic acids, etc. Multiple studies also demonstrate that, in turn, by reducing carbohydrate reserves we can inhibit nitrate uptake. Because higher plants can contain nitrate reserves in concentrations as high as 100 mM (Millimolar), inhibitng uptake during the late stages of growth through defoliation may be a valuable means of reducing total nitrate content in dried Cannabis. This also helps explain why defoliation, *when done late enough*, appears to be beneficial while *premature* defoliation does not appear to have the same effects and instead appears to be universally *harmful *to growth.







 The oxidization of carbohydrates (as well as amino acids, lipids, and chlorophyll) is one of the main aspects of air-curing Tobacco and Cannabis. According to the following report on Tobacco smoke by the Surgeon General available here,“Nitrogen oxide gases are formed by the combustion of nitrogen-containing amino acids and proteins in the tobacco leaf (Hoffmann and Hoffmann 1997). Mainstream cigarette smoke contains mostly NO with traces of nitrogen dioxide (NO2) and nitrous oxide. The formation of nitrogen oxides is amplified by combustion with nitrate salts, and the amount formed is directly related to the nitrate concentration of the tobacco leaf (MacKown et al. 1999). The mainstream cigarette smoke contains approximately 500 μg of NO generated per cigarette. Although fresh smoke contains little NO2, the aging of the smoke converts the reactive NO to NO2, which has an estimated half-life of 10 minutes (Borland et al. 1985; Rickert et al. 1987). These gases react with water and other components in cigarette smoke to form nitrate particles and acidic constituents. Sulfur-containing gases result from the combustion of sulfur-containing amino acids and proteins (Horton and Guerin 1974). In mainstream cigarette smoke, H2S is the most abundant of these gases (approximately 85 μg generated per cigarette), and both sulfur dioxide and carbon disulfide are present in smaller quantities (approximately 2 μg).”*...*
“Aromatics are a class of compounds defined by their structural similarity to benzene. These compounds result from incomplete combustion of the organic matter of the cigarette, most notably sugars and cellulose (Chortyk and Schlotzhauer 1973). The most abundant aromatic compounds in mainstream smoke generated from full-flavored cigarettes with use of the FTC/ISO smoking regimen are toluene (approximately 5 to 80 μg generated per cigarette), benzene (approximately 4 to 60 μg), total xylenes (approximately 2 to 20 μg), styrene (approximately 0.5 to 10 μg), and ethylbenzene (approximately 1 to 8 μg) (Counts et al. 2005; Polzin et al. 2007).”




*Some Considerations*

-When trimming & pruning, it is extremely important to do so with clean and *sterile* tools. If your goal is to prevent mold, bud rod, and other pests using dirty, spore-containing shears or scissors to trim leaves may actually *increase* the plants' susceptibility to disease.

-While *late-state, selective* defoliation appears to benefit many higher plant species in commercial crop production, too much defoliation and/or defoliation that is done too early in the plants' growth stage will have the *opposite* effects.


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*https://link.springer.com/article/10.1186/1471-2229-13-30 Selective defoliation affects plant growth, fruit transcriptional ripening program and flavonoid metabolism in grapevine*

*https://oup.silverchair-cdn.com/oup/backfile/Content_public/Journal/jxb/68/7/10.1093_jxb_erx056/4/erx056.pdf?Expires=1509030693&Signature=S~Dv8PYeH0dGNk7cQsiAFMu8WIRdDBZq9iT2c5FTedKh4y0NU8ZKlP7SZkk7JnrW7aTr~NufeODOZBnRNOATNjLIg4bkBfT9D0e9BEGDu5Z0qq4jWFlek2BlsYl5kW--OAyrm5JZHf5VTznmiqoK9mAWcEodvdpiSId7LfpDLazdMRdaoBST4Qz7XbzSsRyaY23PLUDvcYIbz4Ng6bzP9nSPb5zHDU2RUUyu6gR3YH~KPgd18H9M0QH6H1yvGNNK4ckJ6KwxraTWDkLQ9E1nYJrP64ufDvQAgDzvrwbm1GqBuJVfqGvpRn1HdGPMOpPm3964BHnNyaqjW3KjMEFw2Q__&Key-Pair-Id=APKAIUCZBIA4LVPAVW3Q Depletion of carbohydrate reserves limits nitrate uptake during early regrowth in Lolium perenne L.*

*https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4965446/ Plant Defense against Herbivorous Pests: Exploiting Resistance and Tolerance Traits for Sustainable Crop Protection*

*https://www.science.gov/topicpages/p/plant+defense+elicitors Plant Defense Elicitors*

*http://www.scienceandpublicpolicy.org/images/stories/papers/originals/growth_rates.pdf GROWTH RATES OF OLD VERSUS YOUNG FOREST TREES*

*http://www.biologydiscussion.com/photosynthesis/external-and-internal-factors-influencing-photosynthesis/52305 External and Internal Factors Influencing Photosynthesis*

*https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3091808/ Auxin, cytokinin and the control of shoot branching*

*http://arkansasagnews.uark.edu/618-16.pdf Evaluation of 1-Methylcyclopropene to Reduce Ethylene Driven Yield Reductions in Field-Grown Cotton*

*http://hortsci.ashspublications.org/content/40/7/2061.full.pdf Ethylene inhibitors increase yield, fruit size, quality, and price by as much as 20% in “Artlet” Apples*

*http://blog.extension.uga.edu/brooksag/files/2015/08/Cotton-Defoliation-Handout-8-18-15.pdf ON DEFOLIATION IN GEORGIA UGA Cotton Agronomists*

*http://www.plantphysiol.org/content/41/1/45 Effects of Ethylene on Auxin Transport*

*https://www.cpsagu.ca/about-cps/news/plant-hormones Plant Hormones: Mighty Messengers*

*http://www.google.sr/patents/US5848492 US patent #US5848492 A*

*https://www.ncbi.nlm.nih.gov/books/NBK53014/ How Tobacco Smoke Causes Disease: The Biology and Behavioral Basis for Smoking-Attributable Disease: A Report of the Surgeon General*​


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## Moldy (Oct 25, 2017)

I'm gonna have to read that a couple of times lol.

-While *late-state, selective* defoliation appears to benefit many higher plant species in commercial crop production, too much defoliation and/or defoliation that is done too early in the plants' growth stage will have the *opposite*effects.

What's too early? In fourth week of flowering with leaves up the ass. I'd like to give it try on a side by side with same strains.


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## ILM (Oct 25, 2017)

Nice informational post thank you for that


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## Huckster79 (Oct 25, 2017)

Fascinating... how much and what specific leaves do you propose removing? 

I’ve used both methods, not sold into one camp or the other in terms of going all the way with it. I’ve seen some folks completely strip plants of damn near everything but sugar leaves and others scared to take a single fan leaf. I think what you are proposing is where the truth often is found: in the middle.

Please share your specific technique on what, where and how much to remove and when...

I’m very interested


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## SonsOfAvery (Oct 26, 2017)

One of the best cases for defoliating I've read on here.
Well explained and presented. 
Like @Huckster79 says, I'd also like to here your technique.


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## Huckster79 (Oct 26, 2017)

I have two twins right now i could next round but damn a third would be nice to do one without removing a thing, one strip real agressive and other middle of road.


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## Chip Green (Oct 26, 2017)

Sometimes I see a leaf, usually a big one, and my brain says "cut it off"... and then "wait no, that's foolish." Then there is a short period of debate. Usually I cut it off, due to an insatiable desire I cannot explain. Sometimes after a "waiting period" of indeterminate length. Like a whole day occasionally. Its sort of like that strange mental illness, where people have self amputated limbs.
I now have a greater understanding of the whole method, thanks to this collection of information.


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## Lucky Luke (Oct 27, 2017)

I think that 1/2 the confusion comes with using the term defoliation instead of trimming or pruning.


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## a mongo frog (Oct 27, 2017)

Lucky Luke said:


> I think that 1/2 the confusion comes with using the term defoliation instead of trimming or pruning.


Im pretty sure that defoliation and pruning are 2 different practices in the cannabis industry. Some people doing both and some just pruning bottom third.


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## Lucky Luke (Oct 27, 2017)

a mongo frog said:


> Im pretty sure that defoliation and pruning are 2 different practices in the cannabis industry. Some people doing both and some just pruning bottom third.


And that's the problem, We should be using standard horticulture terms that have a specific meaning not stoner terms that seem to have different meanings depending on who is using them.

Lolipopping for eg is as far as I'm aware a stoner term but it means one thing- cleaning up lower growth. Rose enthusiasts and landscape gardeners use the technique a lot. Flushing seems to mean two or 3 things (I saw a thread recently on here or GC where someone stated that they had started their 2 week PK Flush....). Why don't we use the correct terms- leaching and watering..i don't know how a PK feeding is flushing but hey that's the problem of people using terms without a definition.

When people say defoliate they sometimes mean to remove all or the vast majority of foliage (the correct definition of the word) and then others say they partially defoliate or by defoliate they mean to trim a few leaves...


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## a mongo frog (Oct 27, 2017)

Lucky Luke said:


> And that's the problem, We should be using standard horticulture terms that have a specific meaning not stoner terms


I mean your probably right, but some of us are stoners. Stoner terms and bro science, And cannabis has never been greater!!


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## maximum autism (Oct 28, 2017)

I'm on several experimental runs with trimming, I've had good results by removing the bottom 1/3rd of all leaves and nodes, mixed results with GML-style leaf-stripping (one plant had up to 4 inch buds on a few tops, the other one maintained average sized ones) and an overabundance of popcorn buds (plus sub-par top colas) with plants that I only removed drooping/dead leaves from and didn't strip lower buds. 
On the ground level, I'd only recommend to people that they remove certain fan leaves that block light under the canopy. 
I can't vouch for the viability of a trimming method other than by first hand experience, you can show me all the science you want. 
I can't say for sure which side has the proven methodology, since I see good product coming out of most of the growers who decide to show off their yields, across all schools of thought. 

Am I the only person weary of disinfo in growing forums?


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## xtsho (Oct 29, 2017)

I never remove a single leave and grow nice big fat cola's and the lower buds fill out just fine. 
If you like to play with your plants have at it. I'd rather spend time with my girl, dogs, family, and friends than babysitting a weed.


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## cindysid (Nov 4, 2017)

If a leaf looks funky, I remove it. I worked for a plant leasing company for several years and one of the most important jobs was removing yellow or damaged leaves so the plants would look perfect for display. It always made the plants more healthy and vigorous, and I apply the same practice with my cannabis plants. I'm also slightly OCD and I find perfection to be very satisfying....lol I also lollipop most of my plants since I run crowded rooms. It not only eliminates the dreaded popcorn bud; it also gives me the ability to see the lower part of the plant stalk and the top of the soil. I think the air flow increase prevents a lot of problems also.


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## Humanrob (Nov 5, 2017)

I "lollipop" primarily because it make watering easier, and secondly because it discourages PM. Doing so has shown no signs of being detrimental to the plants health. The possibility that it might actually be good for the plant? Very cool.


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## Flowki (Nov 9, 2017)

Some polite questions/counter arguments.


*''The argument against selective defoliation is a simple one; the leaves are the “powerhouse” of the plant and for every leave that is removed the plants' growth will be stunted.

As leaves age, the density of chloroplast containing cells decreases significantly''*


It may decrease but does it entirely deplete?. Some chloro is better than no chloro. Also what are the stresses induced with taking off leaves that were still healthy, regardless of chloro content. It will take energy to heal that wound and the energy those leaves store collectively, offer a buffer and many good warning signs of deficiency etc.

Still, I feel pruning the lower section of a plant is wise where taller plants are stacked together indoor. I personally think it is not great for the pant in the physical sense but is better for it in the long run due to environment limitation of growing indoor.

If the argument is that removing all leaves 2 weeks in flower creates new leaves that have more chloro>WIN, I have a few issues with this. First off the initial stress/healing will set back flower time. Then, as the leaves grow in the plant is spending a lot of energy growing leaves while also trying to grow buds. The leaves from what I've seen don't grow in as big so may end up having similar if not slightly more chloro over all than just leaving upper/mid leaves alone. When you add all this together, you set yourself so far back that the new leaves with better chloro content have a lot of catching up to do. The renewed chloro may surpass none defoliated in the end.. but it may well not. This may be why some people say it does not work (possibly quick flowering strain) while some say it does (longer flowering strain).

*''We see this same phenomenon occurring on a larger scale in forest ecosystems, where the clearing of old-growth trees causes undergrowth to flourish. Young undergrowth, which grows quickly, actually sequesters significantly higher levels of Carbon compared to massive old growth trees''*

Comparing an old tree to veging under growth with the intensity of the sun/Forrest level co2/climate to advocate indoor MJ defoliation during flower is N/A.

On top of that trees shade out to kill off competition and allow it's own to thrive. I've read a studie saying they are able to share nutrients from mass networks of root systems. The mechanics of it all are so far apart from indoor MJ.


*''Ethylene is a plant hormone produced at various stages of plant growth with complex effects, however, it is produced in the highest quantities in aging leaves and flowers

Ethylene also stimulates the ripening process. It is quite widely known in the field of agricultural sciences that delaying ripening can increase yields by as much as 20%.''*


By ''as much as 20%'' means it could literally equate to 1% as much as it could 20% or 0% in mj. Even in best case 20%, how much extra flower time is needed to achieve that. On a perpetual that extra time becomes offset because you could have an extra crop each year if not defoliating to increase cycles. As defoliation is so hit and miss and difficult to get right strain from strain, why not remove the uncertainty and just grow one extra crop for guaranteed 100% of a normal dialed in crop weight.


*''One of the more well-recognized benefits of defoliation, of course, is its ability to increase light absorption and increase airflow, two things which greatly reduce the likelihood of mold, mildew, bud rot and other fungal infections. Similarly to the effects defoliation has on chlorophyll and photosynthesis, by increasing the concentration of phenols such as Apigenin and Resveratrol present in the leaves, we can also, in theory, reduce the likelihood of pests attacking plants by stimulating their natural immune activity. The following is an excerpt from''*

I agree with most of this in the sense that indoor conditions limit our ability to properly maintain a dense foliage. Removing most lower foliage and even slight leaf removal in mid/upper is a good thing. It will (imo) reduce over all yield but it is a safety measure in ensuring you actually get an over all yield.

Deliberately stressing a plant out with heavy defoliation to try and put it in defense mode IMO will force the plant to divert energy and reduce yield/offset flower finish.


*''Carbohydrate Reserves, Nitrate reserves & Flavour

..inhibiting uptake during the late stages of growth through defoliation may be a valuable means of reducing total nitrate content in dried Cannabis. by reducing carbohydrate reserves we can inhibit nitrate uptake

This also helps explain why defoliation, when done late enough, appears to be beneficial while premature defoliation does not appear to have the same effects and instead appears to be universally harmful to growth.''*

Can't ''flushing'' or reducing ppm into a fade have the same result on top of a dark period prior to harvest that is said to burn up carbs?. This is speculation from things I've read but if it holds any weight it seems like a less risky way of achieving a similar goal. Also, do you feel using UV later in flower may have an effect on using up these undesired levels?. From what I've read on UV it will measurably force a reaction from the plant, maybe even using up some extra stored undesirables. This is a shot in the dark ofc.


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