=ian=
Well-Known Member
So in the course of my internet travels, I have seen some theories on the technique called "defoliation". I have decided to personally go with this technique, and I wanted to convey what information I have come across.
Basically, what you are doing is cutting off anything that is covering a bud-site and not allowing it the full power of the light above.
Example:
This is all cut-and-paste from Google research:
Lets start by defining "defoliation" in the context of this technique. The term has negative connotations as Cannabis has been the target of defoliation by the Feds using Paraquat chemical defoliants. This is not what this is about.
This technique is about leaf removal by hand. It is employed to relieve shading in crowded conditions. It is a substitute to the popular technique of removing lower branches.
But before we get into it I think we should consider what goals are we are trying to achieve by leaf trimming and pruning? Its not an exercise we practice for enjoyment or because some anonymous nom-de-guerre tells us we should. It should be viewed as a means to manage the canopy with the minimum goal being to increase light penetration and air circulation around flowering sites. We can go further and have the goal of increasing the number of flowering sites, managing the shape and height of the canopy, and so on. But at minimum our goal should be to increase light penetration and air circulation around the flowering sites. So lets discuss this just a bit.
The green matter is what contains the cellular structure that provides the means through which a plant can grow (The root structure is for another discussion). Expressed mathematically the equation for photosynthesis is: 6CO2 + 6H2O + Light Energy (PAR) = C6H12O6 +6O2 (glucose + oxygen). Assuming that H2O is not a limiting factor under normal conditions the TWO limiting factors of photosynthesis are PAR light and CO2. The light saturation point is that point at which adding more PAR light will not increase photosynthesis due to the other limiting factor CO2. Only if additional CO2 is added will photosynthesis increase again to a new light saturation point at which adding more CO2 is necessary to increase photosynthesis once again. This works well up to the 1200 1500 ppm of CO2 maximum limit at which point both light and CO2 are saturated. Adding any more of either will not increase photosynthesis. So what about the leaf?
There are many, many things to talk about with the leaf as it is not only the store for plant energy but it is also where the photosynthetic processes takes place. Also, as part of the major function of their role leaves are in competition with one another for nutrients. Aha! So, if we remove the leaf we are removing the energy store of nutrients and the photosynthesis engine! True, but you are also removing the competition for nutrients! But at what point of green matter removal does negative effect occur? That my friends is a real quandary to try to figure out without some real sophisticated laboratory equipment and scientists and academics have been trying to agree on this for at least 100 years. That is why in this case (our hobby and passion) a picture is worth a thousand words. Smoove and 2lsc have more than adequately demonstrated this.
Now lets discuss a bit about the leaf area index (LAI), the physical properties of light, the curvature of the leaf, light reflection, and so on, as they impact the effort to increase light penetration and air circulation around flowering sites, and I will bring my post to a close for now.
If your plant is going to capture the entire available PAR to use in photosynthesis then the leaf canopy must be: arranged well, have an adequate LAI, and be in position to capture the light. Leaves that are shaded or severely stressed in opposition to the perpendicular source of the light will NOT capture the PAR due to light reflection along the curvature of the leaf. As such, those specific leaves which are not capturing light are not useful to photosynthesis and can be removed without negative effect to plant health or growth! Light being comprised of photons travels in a straight line. The most effective and efficient use of light is when it strikes the leaf area perpendicular to the light source (i.e. straight down). Any curvature of the leaf will reflect the light causing it to angle off in another direction. Any of the light that is captured along the curvature will most certainly be a subset of that light which is available when it strikes the leaf perpendicular (straight down) from the light source. This is physics and a huge part of the physical characteristics of light. So, if the leaf is on the plant and the leaf is not capturing light the leaf is not performing photosynthesis. Period! This is just merely a fact and I didn't arrive at that conclusion on my own. It's been well stated academically many, many times over.
That said, the rules of light and photosynthesis still apply. If the light is not striking a leaf no photosynthesis is occuring. Extrapolate this on out in the spirit of quality of light (angle, distance from source, PAR value, etc), and if a leaf or a branch doesn't fit the requirement for quality and you can not otherwise correct the problem, cut it off! During the vegetative stage it is highly advisable to selectively prune and trim (and bend and tie). Not only are you training and managing the canopy for height you are also increasing light penetration and air circulation around the remaining canopy, a.k.a CO2. You are managing the canopy growth for optimum LAI to use the available light you are working with, maximizing the light penetration (distance and angle), and improving air circulation (CO2). With PAR light the inverse square law still apllies and all of that. Effective use of PAR is extrememly important all the way through the life cycle. Your minimum goal should be to improve light penetration and improve air circulation.
There are MANY pictures at the start of another thread that explain this technique better than I could ever do.
As I stated above, I am going to head into the grow room right now and trim my girls.
What do you all think about this?
Basically, what you are doing is cutting off anything that is covering a bud-site and not allowing it the full power of the light above.
Example:
This is all cut-and-paste from Google research:
Lets start by defining "defoliation" in the context of this technique. The term has negative connotations as Cannabis has been the target of defoliation by the Feds using Paraquat chemical defoliants. This is not what this is about.
This technique is about leaf removal by hand. It is employed to relieve shading in crowded conditions. It is a substitute to the popular technique of removing lower branches.
But before we get into it I think we should consider what goals are we are trying to achieve by leaf trimming and pruning? Its not an exercise we practice for enjoyment or because some anonymous nom-de-guerre tells us we should. It should be viewed as a means to manage the canopy with the minimum goal being to increase light penetration and air circulation around flowering sites. We can go further and have the goal of increasing the number of flowering sites, managing the shape and height of the canopy, and so on. But at minimum our goal should be to increase light penetration and air circulation around the flowering sites. So lets discuss this just a bit.
The green matter is what contains the cellular structure that provides the means through which a plant can grow (The root structure is for another discussion). Expressed mathematically the equation for photosynthesis is: 6CO2 + 6H2O + Light Energy (PAR) = C6H12O6 +6O2 (glucose + oxygen). Assuming that H2O is not a limiting factor under normal conditions the TWO limiting factors of photosynthesis are PAR light and CO2. The light saturation point is that point at which adding more PAR light will not increase photosynthesis due to the other limiting factor CO2. Only if additional CO2 is added will photosynthesis increase again to a new light saturation point at which adding more CO2 is necessary to increase photosynthesis once again. This works well up to the 1200 1500 ppm of CO2 maximum limit at which point both light and CO2 are saturated. Adding any more of either will not increase photosynthesis. So what about the leaf?
There are many, many things to talk about with the leaf as it is not only the store for plant energy but it is also where the photosynthetic processes takes place. Also, as part of the major function of their role leaves are in competition with one another for nutrients. Aha! So, if we remove the leaf we are removing the energy store of nutrients and the photosynthesis engine! True, but you are also removing the competition for nutrients! But at what point of green matter removal does negative effect occur? That my friends is a real quandary to try to figure out without some real sophisticated laboratory equipment and scientists and academics have been trying to agree on this for at least 100 years. That is why in this case (our hobby and passion) a picture is worth a thousand words. Smoove and 2lsc have more than adequately demonstrated this.
Now lets discuss a bit about the leaf area index (LAI), the physical properties of light, the curvature of the leaf, light reflection, and so on, as they impact the effort to increase light penetration and air circulation around flowering sites, and I will bring my post to a close for now.
If your plant is going to capture the entire available PAR to use in photosynthesis then the leaf canopy must be: arranged well, have an adequate LAI, and be in position to capture the light. Leaves that are shaded or severely stressed in opposition to the perpendicular source of the light will NOT capture the PAR due to light reflection along the curvature of the leaf. As such, those specific leaves which are not capturing light are not useful to photosynthesis and can be removed without negative effect to plant health or growth! Light being comprised of photons travels in a straight line. The most effective and efficient use of light is when it strikes the leaf area perpendicular to the light source (i.e. straight down). Any curvature of the leaf will reflect the light causing it to angle off in another direction. Any of the light that is captured along the curvature will most certainly be a subset of that light which is available when it strikes the leaf perpendicular (straight down) from the light source. This is physics and a huge part of the physical characteristics of light. So, if the leaf is on the plant and the leaf is not capturing light the leaf is not performing photosynthesis. Period! This is just merely a fact and I didn't arrive at that conclusion on my own. It's been well stated academically many, many times over.
That said, the rules of light and photosynthesis still apply. If the light is not striking a leaf no photosynthesis is occuring. Extrapolate this on out in the spirit of quality of light (angle, distance from source, PAR value, etc), and if a leaf or a branch doesn't fit the requirement for quality and you can not otherwise correct the problem, cut it off! During the vegetative stage it is highly advisable to selectively prune and trim (and bend and tie). Not only are you training and managing the canopy for height you are also increasing light penetration and air circulation around the remaining canopy, a.k.a CO2. You are managing the canopy growth for optimum LAI to use the available light you are working with, maximizing the light penetration (distance and angle), and improving air circulation (CO2). With PAR light the inverse square law still apllies and all of that. Effective use of PAR is extrememly important all the way through the life cycle. Your minimum goal should be to improve light penetration and improve air circulation.
There are MANY pictures at the start of another thread that explain this technique better than I could ever do.
As I stated above, I am going to head into the grow room right now and trim my girls.
What do you all think about this?
