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To defoliate or not?

VerdantGreen

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It's a very broad term that can cover a wide range of practice from light to extreme leaf removal.

Personally i only remove leaves if they are shading a bud site or if they are getting old and fading.... my brain can't compute how removing lots of healthy leaves will increase yield, and nobody has ever given me a satisfactory scientific reason why it would.. neither have i seen a proper side by side comparison that gave better results for heavy defol.

That said, some people who do defoliate get results that are hard to argue with.

VG
 

Greenheart

Active member
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I too have seen threads that show how effective it can be. I have tried it in the past. For me it was more work and stress on the plants. They tend to stall for a bit then take off when they recover from it. I think it really depends on both the setup and the plant itself.

Where I really found it most effective was in pest control of mites and thrips. I would do extreme defoliation down to new growth tips and a few smaller fans. Then apply my treatments daily until eradication.
 

f-e

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I don't think I could watch a grow without helping it along. A plant can only see so much of what's happening. It's our job to steer it's shape in the direction we want it.
 

negative37dBA

Well-known member
Veteran
It really depends on the type of grow you have. A very dense full canopy will need to have leaves removed to facilitate air flow and light pen. I use a extreme method when I remove my fans. I want to be able to see through the plants all the way to the walls when I am done. Also some light pen to the floor helps with the light avoidance response. If you a only running a couple plants or have a lightly filled trellis then the method of just removing a few that block light to lower bud sites is more in order. Check out some of Greengenes defoil videos. He goes extreme and gets excellent results. It can be strain dependent as well. Some are going to react better than others to that type of treatment. My gg4 clone does not mind at all being stripped down round day 21. You can almost not tell after just a week or so. I think it really helps my yield and bud development down low. I have NEVER had mold, PM or Botrytis. I do live in the desert so that helps.
Have a great day all. Peace, negative.
 

Switcher56

Comfortably numb!
This discussion has taken place before and the jury is pretty much out on the subject. I manifold/mainline all my grows now (indoors). Large fan leaves (also known as solar panels) require to be water and fed, along the way to the top(s), not unlike a kid at the end of a line getting the left overs. Mainlining when using the home water concept, of a 3/4" supply with 1/2" take offs. Pressure remains constant when a tap is opened because the main as more volume, than the take offs. That water has to go somewhere. Physics :)
 

Koondense

Well-known member
Veteran
Ithink Paddi did some side by side grows with same genetics and defo.
From memory the yield was very similar but defo plants had tighter buds and finished a bit earlier... but not 100% sure, someone should check for his grows.
I personally defoliate to some extent, mostly for exposition and air circulation, the leaves sometimes cannot breathe properly and get wet from other leaves moisture, those i remove.

Cheers
 

VerdantGreen

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This discussion has taken place before and the jury is pretty much out on the subject. I manifold/mainline all my grows now (indoors). Large fan leaves (also known as solar panels) require to be water and fed, along the way the top, not unlike a kid at the end of a line getting the left overs. Mainlining when using the home water concept, of a 3/4" supply with 1/2" take offs. Pressure remains constant when a tap is opened because the main as more volume, than the take offs. That water has to go somewhere. Physics :)

that takes no account of the energy that those leaves produce... by the same token the removed leaf will not be transporting sugars into the plant. Biology :)
 

Chi13

Well-known member
ICMag Donor
It's never made much sense to me, but if someone can show a study that proves it works I will do it.
I came across a couple of interesting reads on the subject, basically saying that a lot of people do this but that there is no evidence it works. A couple of exerts from the articles and links below.

These studies below all agree that pruning of less than 25% in the vegetative stage, doesn’t cause significant yield loss. This is encouraging news for Cannabis farmers because almost across the board, it seems pretty common, especially with indoor farmers, to thin the canopy to allow increased airflow – before the end of week three.

However once you get fully into the flower stage, the detrimental effects increase rapidly.
https://cannabis-science-consulting....ation-studies/

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.

https://www.cocoforcannabis.com/comm...-to-defoliate/
 
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negative37dBA

Well-known member
Veteran
The plant evolved to have all the leaves, why remove them, it reduces the growth rate and hence yield, I only remove leaves when they die.

We are not growing in nature and I answered that exact question in my first post. Those statements about growth rate and yield are your opinion not facts....
 

Chi13

Well-known member
ICMag Donor
It really depends on the type of grow you have. A very dense full canopy will need to have leaves removed to facilitate air flow and light pen. I use a extreme method when I remove my fans. I want to be able to see through the plants all the way to the walls when I am done. Also some light pen to the floor helps with the light avoidance response. If you a only running a couple plants or have a lightly filled trellis then the method of just removing a few that block light to lower bud sites is more in order. Check out some of Greengenes defoil videos. He goes extreme and gets excellent results. It can be strain dependent as well. Some are going to react better than others to that type of treatment. My gg4 clone does not mind at all being stripped down round day 21. You can almost not tell after just a week or so. I think it really helps my yield and bud development down low. I have NEVER had mold, PM or Botrytis. I do live in the desert so that helps.
Have a great day all. Peace, negative.
I can get that there might be an argument about air flow, but not about light penetration. Why do you seem to think it is more important for direct light to hit the lower leaves tha upper leaves? What about ambient light? There seems to be this perception that only leaves that are directly getting light are adding to the plant, whereas ambient light is present below the canopy. Using the solar panel analogy, the less solar panels, the less energy. A solar panel in full or partial shade may not work as well, but it still contributes.

I often hear of people getting "excellent results" through defoliating, but nowhere do you see an actual experiment comparing clones that are defoliated to clones that are not (control). Many get excellent results by not defoliating as well.
 

@hempy

The Haze Whisperer
In plants, apical dominance prevents the development of lateral shoots. It can be overwhelmed by apical bud defoliation, allowing numerous lateral buds to develop into more lateral branches carrying more fruits and possibly increasing seed yield. This study tested this hypothesis on five hemp (Cannabis sativa L.) cultivars in a 2-year field experiment. In comparison to the intact ones, the defoliated plants developed several lateral shoots. The hemp seed yield was significantly influenced by the year of production, the apical bud removal, and the cultivar. The average two-year seed yield of the defoliated plants (715 ± 47 kg/ha) was significantly higher than the yield of the intact plants (568 ± 35 kg/ha). Absolutely the greatest effect of apical bud removal on the seed yield was observed for the cultivar ‘Novosadska konoplja’, where increase was 225 kg/ha (25%); a slightly smaller difference occurred for the cultivar ‘Uniko-B’ (183 kg; 30%), followed by ‘Juso-11’ (140 kg/ha; 27%) and ‘Bialobrzeskie’ (128 kg/ha; 29). Cultivar ‘Beniko’ presented the smallest difference with apical bud removal – 58 kg/ha (15%) yield increase We maintain that hemp producers can achieve a larger seed yield not only by selecting an appropriate cultivar and row distance but also by removing apical buds.
https://www.researchgate.net/publica...nabis_sativa_L

Effects of Defoliation in Grain HempKadie E. Britt and Thomas P. Kuhar
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
Chewing insects such as caterpillars, beetles, and grasshoppers are sometimes present in great densities on hemp plants
and can often consume a considerable amount of foliar material. Very little is known about the impact of defoliation on
hemp. In 2018 and 2019, an experiment was conducted to simulate insect defoliation on grain variety hemp plants (‘Felina
32,’ a dual-purpose grain/fiber variety) to determine whether a loss of foliar area could impact yield. This experiment was
conducted at Virginia Tech’s Kentland Research Farm in Whitethorne, VA. Hemp plants were manually defoliated with
shears to remove varying levels of leaf material from plants at varying times throughout the season. Plants were defoliated
at 20, 40, and 60 days post planting (to simulate early, mid, and late season insect infestations) at levels of 0%, 25%, 50%,

and 75% (to simulate damage at no, low, medium, and high levels of insect infestation). ‘Felina 32’ variety hemp plants
typically have a ~90 day growing season in the field. Seeding rate both years was 30 pounds of seed per acre. Planting dates
for this study were 8 June 2018 and 30 May 2019. The results from both years of this experiment showed that average seed
weight per hemp plant was not significantly affected by timing or amount of foliar area removed from plants. These results
confirm the popular belief that hemp is an extremely durable and tolerant crop. However, it is possible that actual insect
feeding injury rather than manual defoliation using shears could potentially elicit a different plant response. However,
similar experimental methods have been conducted in many other crops using manual defoliation and showed that plant
yield was significantly negatively affected. Also, although this experiment revealed that grain yield was not affected, it does
not provide any information as to whether chemical production of THC (tetrahydrocannabinol) or CBD (cannabidiol) is
altered. Future directions will explore potential chemical content alteration within grain and CBD variety hemp plants.

https://plantpathology.ca.uky.edu/files/sr112.pdf



Defoliation is simply the act of cutting leaves off a cannabis plant for the purpose of pruning. 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.

Larger yields

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.


Efficient light absorption

https://greenrushpackaging.com/canna...wing-cannabis/

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