Fan Leaf Removal

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tester

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There seems to be alot of tension building when it comes to fan leaves being trimmed or not being trimmed, i think this article meets both sides in the middle.

Source: Alot of posts from people on the internet, originally written and compiled by Nietzsche

Should Fan Leaves be Trimmed?
There are a number of theories why fan leaves should or should not be removed. The purpose of this paper is to analyze cannabis cultivation techniques that advocate for and against fan leaf removal. A summary of each theory is presented, followed by a review of fan leaf function. The different theories advocating for and against the removal of fan leaves are then discussed in the context of fan leaf function and cultivation techniques.


THEORIES WHY TO TRIM FAN LEAVES
Increase Lower Bud Development
The fan leaves shade lower buds and that these buds do not develop to there full potential because of a reduction in lighting intensity due to shading from upper fan leaves.

To conserve energy for upper bud development
Trimming fan leaves and lower, shaded branches focuses the plant’s development on main top buds. A plant wastes precious energy several ways. A tall plant needs to use energy to build extra stem, and then use extra energy to move water up higher, this is why I believe "scrog" methods are productive. An untrimmed bushy plant causes the plant to expend energy to build elaborate branches and leaves, and then has to use excess energy to supply all these structures. Careful trimming to remove unnecessary branches (which wont produce nice buds) and unproductive suckers will leave more energy for a larger yield. Suckers do exactly as their name suggests, they suck needless energy from the plant which can be put to better use, towards yield.

Reduce the Stretch
If fan leaves are trimmed during the early flowering stage, the stretch is reduced. Reducing the stretch might be advantageous in certain cultivation conditions.

Speeding Up The Flushing Process
Remove some of the fan leaves 14 days before harvest. It helps speed up the flushing process and or makes flushing unnecessary.

Reduce The Chance of Mould
Removal of dead fan leaves is necessary to reduce the risk of mould. Failing to "clear the airway" can lead to development of mould in the "crowded" areas of the plant.

Scrog growers may also reduce the chance of mould by removing fan leaves due to reduce the level of transpiration. This is because many scrog grows are in a confined space where humidity is a serious problem. However with better ventilation it may be necessary to avoid the mould problem.

Increase root development on Clones
Fan leaves on clones should have their blades cut in half, to make the clone grow slowly while a root system develops.

HOW DO FAN LEAVES FUNCTION
The large fan 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 substances. Most cannabis plants begin to lose their larger leaves when they enter the flowering stage and this trend continues on until senescence.

Fan leaves account for the greatest area for the reception of photons on a plant, thus they account for the majority of photosynthesis which occurs within a plant. Cells in the plant's leaves, called chloroplasts, contain a green pigment called chlorophyll which interacts with sunlight to split the water in the plant into its basic components. Leaves only absorb about 15% of the solar energy that hits them, the other 85% passes through-- but they reflect all the green light, which means it looks darker below the leaf to a human than it does to the plant because our eyes are most sensitive to the green spectrum.

Photosynthesis occurs in all green parts of plants. The process has two stages, the light reactions and the Calvin cycle, that convert water and carbon dioxide into sugar and oxygen. These sugars are later used to power all the processes in the plant, including the synthesis of THC and other cannabinoids. Fan leaves possess the greatest number of stomata, which are small pores or valves on the underside of the leaf which water vapor and carbon dioxide diffuse during transpiration and photosynthesis (carbon fixation). Carbon dioxide first enters the leaf through the stomata and combines with the stored energy in the chloroplasts through a chemical reaction (the Calvin cycle) to produce a simple sugar. This sugar is unloaded into the tissues and transported through tubes in the leaf to supply the synthesized food to other plant parts such as growing or respiring tissues like young leaves, roots, and flowers of the plant. meristems.

Removal of fan leaves will not only slow growth, but it will also hinder the plants ability to rid itself of toxic gases, and also hinder the regulation of the plants temperature via stomata. Changes in the plants chemical metabolism caused by fan leave removal causes the plant to work overtime to rid ‘toxins’ with less leaves, as a result the pant may allocate more growth hormones into growing more leaves to make up for what has been lost. Removing large amounts of fan leaves may also interfere with the metabolic balance of the plant. Leaf removal may also cause sex reversal resulting from a metabolic imbalance.

There is a relationship regarding the amount of carbohydrates a leaf produces and CO2 intake relative to outside forces. When you have a situation whereby the leaf is no longer productive for the plant for whatever reason that may be - low light, old age, disease, insect attack etc, the plant will discard it.

Plants have two different kinds of vessels in their stems to move stuff around, xylem and phloem. Xylem runs from the roots up the stem carrying water and nutrients. Phloem runs both up and down to move sugars hormones, proteins, etc but mostly sugars. Each part of the plant can be either a sugar source or a sugar sink. Phloem moves from sources (areas of supply) to sinks (areas of metabolism or storage). Granted that the flowers can produce some photosynthate, but they are no where near as effective as fan leaves (resin glands significantly reduce light to the tissue they are found on). Flowers are sink tissues, leaves are source tissues. Sinks do not produce enough photosynthate, and are importers. Sources give photosynthate to sinks in closest proximity. Upper leaves bring sucrose to shoot apical meristem and young leaves while lower leaves bring goodies to roots. Remove the source and the sink will be affected

The leaves at the top of a plant tend to supply the top growing shoots. The leaves at the bottom of the plant tend to supply the roots. The middle leaves can go either way as the demand changes. During flowering and fruiting, only the very bottom leaves supply the roots and the rest of the leaves try to get as much energy as possible to the flowers of fruits. For this reason, the more leaves are unshaded and in good light, the more chance the plant has of creating extra storage of energy that will ultimately go into yield. However some believe that the rich green leaves emerging from the bud are a sufficient energy source of solar energy for the plant's floral development. Therefore the old fan leaves are once again rendered useless and only drain energy from the developing part of the plant.
 
Article Continued..........


Fan leaves store mobile nutrients, these stored nutrients are essential in the later stages of flowering. When flushing a plant the fan leaves will lose their color quickly. This is because the nutrients are being mobilized to the atypical meristem (grow tip, bud site). Draining your fan leaves with a flushing period will increase floral development. Fan leaves therefore serve as a nutrient deficiency buffer zone for the plant.
Nutrient burn usually causes bottom leaves begin to die however DaGnome observed that if you do not remove the leaves then they will absorb damage as premature removal generally results in more leaf loss. However if growing hydroponically under ideal conditions it could be argued that fan leaves serve as a nutrient buffer is a moot point.


WHEN AND WHAT TO TRIM IF AT ALL
To trim or not to trim that is the question. Try everything for yourself. Try it all ways. Simply put there is no universal answer it depends on how your are growing when where and what you trim.

Genetic Variance
Cannabis phenotypes play a large part. A strain with very few leaves and long internodes will need a lot less trimming - if a trimming technique is even adopted. A strain with a surplus of leaves and short internodes would require more thinning to get the same amount of light to the lower buds. Cannabis varieties from high sunshine equatorial areas like thai sativa have thin leaves most likely due to more light than say a indicia plant from afghan regions have wider fan leaves due to less light intensity in their natural environment.

Remove non productive ‘dead’ leaf material
Here are some signs to look for when removing foliage. Leaves that have reached their final size and are ageing will stop producing chlorophyll and start changing to a lighter color, often yellowing and showing purple petioles (leaf stems). This is when the leaves' capacity to produce sugars starts to diminish, so they are the ones to take out of the way to allow Sunlight to fall on the younger leaves that are producing at a higher rate. The older leaves, even though larger, are no longer very productive once they are not dark green anymore. By the time they start looking pale or discolored, they are not contributing anything to the plant at all. Obviously, the lower leaves are the oldest and the first to age. Old leaves can be removed at any time they are shading younger ones, but try to never remove a leaf in its expanding stage because it is producing at full power.

Outdoors, fan leaves serve an additional and very important purpose of protecting the buds from the elements and predators. These leaves often become damaged in the course of doing their duty, and will then wither or break off . However depending on the humidity of the growing climate Leaf suggests to trim most leaves that show signs of age, are dull in color, yellowing, and obviously any brown or spotted leaves that have bugs or bug damage to prevent mould.


To Increase Lower Bud Development
Light efficiency decreases with distance. The inverse squared light rule states that illuminance is inversely proportionate to the square of the distance from the light source.
Removing the largest area of photosynthesis that is closest to the light source simply to benefit smaller leaves growing out of the but sites that are further away is not logical when growing indoors". Cultivating outdoors under the sun, the fan leaves don't create nearly as much shade as they do indoors. This is consistent with the inverse squared light rule; the sun is 149,597,890 km away so a few feet has no real effect on intensity. This suggests that a trimming benefit could be achieved outdoors as opposed to indoors however leaves only absorb about 15% of the solar energy that hits them, the other 85% passes through except for green light which is reflected, therefore removal of fan leaves would only provide a 15% increase light transmission outdoors

removes fan leaves that are yellowing or starting to yellow (these are usually on the lower stems) and also mid-stem fan leaves that are shading buds. He always try to retain the upper 2 - 3 sets of fan leaves indoors as he believe they are the ones that are truly "working". The concept of the upper fan leaves doing all the work is consistent with effect of the inverse square rule on lighting intensity indoors and the flow on effect for photosynthesis. In support for trimming HyGradeChronic states selective trimming benefits lower floral development, allowing the buds to fill out and tighten up better. However he does mention that humidity must be kept to a minimum as leftover stems from the leaf can develop mould unless kept at optimum humidity. Another flow on effect to leaf trimming mentioned by HydradeChronic is that it takes seven to ten days longer for floral development to finish, but the resulting florescence is at it’s peak from top to bottom.

An alternative to trimming to increase light to lower floral clusters is to use a light mover on a single plant the results are better thanks to the better penetration of light at different angles. Even simple under lighting and side lighting works well to counter fan leaves by adding extra light where it would not normally get.
Increase upper bud development
What folks need to focus on is the causes of premature leaf drop as that negatively affects yields. If you've read my posts over the years, I try to pound that issue home whenever given a chance. After a good root development, the most important element in floral production is the retention of healthy leaves.

some suggest that large leaves actually take more energy to maintain than they produce. In contrast some state that when a leaf no longer serves a productive purpose, the plant will remove the leftover metabolites from the leaf, which causes the old spotty, yellowing, necrotic image and then the leaf drops. Once that leaf is gone, a percentage of what would be available carbohydrates for future plant growth is diminished in direct relationship to the loss. The mobility of plants sugars and nutrients suggests that fully developed fan leaves are sources not sinks. Whether developing fan leaves are a sink or a source however is not as clear. An actively growing leaf may be a sink, using energy from the other parts of the plant to fuel their development. Older developed leaves and that are sources. However there is no evidence to support that during the plants life cycle the development of fan leaves takes more energy then a fully developed fan leave provides, that is to say sink phase is greater than the source phase (Nietzsche). It would also seem illogical from an evolutionary point of view that a plant would evolve to produce leaves that take more energy to sustain then they produce.

Trim fan leaves in the last 14 days to help speed up flushing
It helps speed up the flushing process and or makes flushing unnecessary. However the leaves should naturally yellow, too much green in the leaves translates to too much "green" taste in the leaves in my opinion.

Reducing the Stretch
If trimming fan leaves reduced the stretch it is likely that this occurred because it takes away from the plant's available energy stores and energy generators. This method of reducing the stretch should only be used if absolutely necessary, other options include chemical treatment may be a more viable option.


HOW TO TRIM IF YOU CHOOSE TO DO SO
If you decide to trim your fan leaves, one should always do it by clipping the petiole about halfway between the base of the fan leaf and the stem/branch. Allow the remainder of the petiole to dry up and fall off on its own. This will help protect the plant from risks of infections. They should never be stripped or broken off at the base of the petiole as that would be expose more chance of infecting the plant. Petiole is the he foot stalk of a leaf.

some believe that excessive leaf trimming and branch pruning will cause the plant to use extra energy to repair itself. However, trimming must be done from time to time, for the longer a plant is left untrimmed, the more material must be removed at one time, therefore the greater the damage that the plant will need to repair. Do not trim fan leaves during veg either, unless they turn yellow. The first real pruning starts when going into 12/12. When trimming and pruning, I try to ensure that I do not cause the plant to 'bleed'. Leaf tries to pinch off shoots and leaves with my fingernails as opposed to leaving a clean cut. One thing to remember is every time you cut into any part of a plant, you are exposing the inside of the plant to fungus and bacteria.

Tuck instead of trimming
Another method is to tuck your fans leaves under to expose the buds, don't forget that even though they wont be getting as much light they are still photosynthesizing and more importantly exchanging gases storing nutrients, and building sugars which the bud then converts into THC and other cannibinoids.
 
Sorry tester- but I'm not convinced of the scientific basis of this article.
 
Yo Ho Tester,

Is this made up and written by you, or someone else ?

I feel that some of this has a touch of value to it, but a lot of it is just wrong thinking. I have been involved to a great degree in Horticulture for over 35 years now, and some of what is being said here just isn't so. Just my $0.02

smoke in peace
KK :cool:
 
The article was not written by me it was originally written and compiled by Nietzsche compiled from posts by various growers, original source has been confiscated by the royal canadian mounted police so cant really post the direct source lol
 
I understand you're not the author tester and I mean no offense by my comment, but I see it as an incongruous amalgamation of opinions. I actually had trouble following it as it verged on contradiction. Some basis in science on a few points, but alot of misinterpretations.

Just my opinion though.
 
oh yeah dont get me wrong i know exactly what you mean, I just thought it would be better to have something like this, than having people falling out with each other in recent posts about this subject.
 
Yes, please someone provide definitive evidence (not just dogmatic statements) that to remove fan leaves is harmful, and I will yield to the evidence.

Until then, I will experiment WITH NO BIAS, and try to prove to myself which is better. If keeping all fan leaves is observed as better, I will do this.
 
In my experience, removing fan leaf stops the developement of the adjacent bud. Whereas, if one just gently folds the fan leaf under so that it rests over a lower limb the bud fed by this leaf continues to prosper while alowing light to the lower buds.>)
 
Bah Humbug.... DON'T prune your fan leaves! :p

EbenezerScrooge.jpg
 
But its full of the same type of opinions that continue to be posted, and in my eyes this post fulfilled its objective as your now saying the post is not scientific instead of someones posts from this site, which means nobody is argueing lol
 
"There seems to be alot of tension building when it comes to fan leaves being trimmed or not being trimmed, i think this article meets both sides in the middle."..



so why would you start another thread about this?

what is the point of this thread?
 
RE: stretch - since I use side-lighting, I have observed ZERO stretch for this grow. I think maybe the top of one plant might have stretched (i.e. continued to grow) about 6 inches after 12 / 12 initiation.

If anything, the lower branches grow more horizontally towards the light, and the whole plant will "spread" as it "stretches" itself (?) towards the horizontal light.

This is why I would like to try my U-L-T-I-M-A-T-E lighting set up to make the light pervade everywhere like the sun.

The Sun's Light pervades everywhere. It is not from one direction only as people have wrongly posted here. The sunlights light is refracted through our atmosphere and is reflected from everywhere in all directions. Plants get sunlight from all directions: direct light, refracted light, reflected light...

Stretch proves nothing about fan leaves / SLASH / trimming.

Though I think there is something about the statement that cutting the adjacent leaves stop feeding the bud. Yes, I agree these leaves HELP to feed the bud, but I think the whole plant is attached, so it compensates by drawing resources from elsewhere.
 
To stop members of this forum argueing over the subject in multiple threads, and its informative
 
tester said:
To stop members of this forum argueing over the subject in multiple threads, and its informative

It is not stopping anybody from arguing (is it possible to do such a thing?:))

and it is not providing any useful or new info
 
cmd420 said:
It is not stopping anybody from arguing (is it possible to do such a thing?:))

and it is not providing any useful or new info

Least it's an all in 1 collection of all the ideas out there, I've read most of these but for someone who might not be sure if they want to trim or not least they can take a pick at what they think might be the case. I don't trim them myself, I just pick 'em off when their dead enough to pull off without any effort.

Good post tester.
 
BBFan said:
I understand you're not the author tester and I mean no offense by my comment, but I see it as an incongruous amalgamation of opinions. I actually had trouble following it as it verged on contradiction. Some basis in science on a few points, but alot of misinterpretations.

Just my opinion though.

yeah, that. hard to follow, with the obveous editing $$
 
All that this article is, is another persons contradictory oppinion on the subject that 99.9% of this forum is in agreament about, and 1% who doesn't know squat about growing, wants to argue about....why keep feeding into it? maybe it will go away, let the kid mutilate his/hers plants, and if he/she wants to come back in a month or 2 and tell us that we are all wrong and he/she has single handedly altered the course of indoor growing as we know it, well we can all sit back and laugh at the arogance of him/her to think us that gullable. I honestly can't believe that this newbie has rented enough space in the collective heads of experienced growers to merit 3 or 4 different threads on such a useless subject. Can't we please just let the subject die as easily as his plants will? At least until the next revolutionary young rookie comes along with this same idea, next week.
 
If anything, the lower branches grow more horizontally towards the light, and the whole plant will "spread" as it "stretches" itself (?) towards the horizontal light.

You realize that is stretch. Marijuana is phototropic which means it will grow toward its light source. So when it grows "out" it is stretching towards its light source. So your statement of
"since I use side-lighting, I have observed ZERO stretch for this grow"
is not only inaccurate but incredibly false and proven so by
"If anything, the lower branches grow more horizontally towards the light, and the whole plant will "spread" as it "stretches" itself (?) towards the horizontal light. "

This is why I would like to try my U-L-T-I-M-A-T-E lighting set up to make the light pervade everywhere like the sun.

The Sun's Light pervades everywhere. It is not from one direction only as people have wrongly posted here. The sunlights light is refracted through our atmosphere and is reflected from everywhere in all directions. Plants get sunlight from all directions: direct light, refracted light, reflected light...

Ok but thats why we paint our grow rooms white or use mylar or panada film. You get the same refracted reflected light. I admit I was in inaccurate when i said the light only comes from one direction I should have said it comes most intensly from one direction. In their natural environment (outside) marijuana will turn towards the sun through out the day, just like a sun flower or any other phototropic plant. My growroom is not a vacum and neither is yours, it contains atmosphere and surfaces that are much more highly reflective than you find outdoors.

Your ultimate light set up is nothing new, its been done, and the return is not worth the investment or else we would all be doing it. You are attempting to reinvent the wheel.

Stretch proves nothing about fan leaves / SLASH / trimming.

What? Sure it does, if this were true (and I have no idea if it is) stretch is something we all try to control in an indoor environment, so if removing fan leaves does indeed cause the plant to respond by stretching then it is one more reason not to do it.

Though I think there is something about the statement that cutting the adjacent leaves stop feeding the bud. Yes, I agree these leaves HELP to feed the bud, but I think the whole plant is attached, so it compensates by drawing resources from elsewhere

So if the plant has to share resources that would otherwise gone to development somewhere else on the plant this is desirable to you? You do a better job of arguing against yourself than anyone here can.

You know I was going to end this post with some little sugar coating ** so as to not hurt you feelings but I'm even more bothered by your posts after writing this, not on a personal level mind you. It bothers me because you sound confident and convincing enough that a new grower may actually be tricked into thinking you understand what you are talking about and I just want to set the record straight that you do not.

All of the information you are trying to find by poking in the dark with a stick is available freely. Either ask someone with experience or you can always read resources on greenhouse growing, agriculture, whatever. Just look for studies done on plants similar to marijuana and apply the knowledge. Tomatos may not get you high but what works for them will most likely work for pot and many other plants that grow in similar conditions.
 

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