To defoliate or not?

[Switcher56]

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.

As you sir! I believe its time for sex and travel. Run the experiment with what you want and report back. Otherwise give it a friggin rest!

 

[Chi13]

As you sir! I believe its time for sex and travel. Run the experiment with what you want and report back. Otherwise give it a friggin rest!

I would love to run the experiment but not in a position to do so. I am a small personal indoor organic grower with not enough space.

Thanks for the advice to "give it a frigging rest", but it's a forum for exchange of views and I have as much right to post as anyone else, provided I don't break the rules. I have an interest in the subject and a love of science, so when I see stuff posted that claims "science", when none is present I feel the need to comment. I am already not posting in another thread that interests me because a certain member cannot cope with anyone disagreeing with him. I do admit to a certain frustration with the debate when I get replies that have no relation to what I have posted. Hence why I cut and paste a few entire articles. Anyway I have posted what I can. Folks are free to make their own decision around defoliation. I really do hope someone does this experiment.

 

[f-e]

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..

It was quite an extreme test. 85%, from the bottom upwards. I'm for defoliation, but to see gains after 85% came off, surprises me. I feel quite sure you can have too much of a good thing, but nobody seems to of told that the Sat.

I have seen a couple of studies suggest plants provide some grazing material. If you put on your Darwin head, then any that didn't would eventually slip behind. Just one bad year for infestation, and those with spare might be unaffected, while those without don't produce so well. Some years, I have had caterpillars decimate plants. The plants that get though millennia probably do carry extra leaf. A number just below 30% pops up (I think it did here) as this isn't a topic that's missed all research. It's one that's spoke about a lot.

85% and it got better. That really is fuel for the fire. I thought 15% wouldn't be missed, and another 15% could be done strategically. Looks like my version of defoliation falls short.

 

[Chi13]

@ f-e, One of the papers Hempy presented earlier studied the effect of grazing from insects on hemp. Interestingly it did not show a negative effect, but nor did it show an increase in production. However it was measuring seed production. Not quite sure why Hempy posted as it does not support his position. Interesting none the less and a brief read. The last few sentences in particular, and noting; similar experimental methods have been conducted in many other crops using manual defoliation and showed that plant yield was significantly negatively affected.

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

 

[Switcher56]

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 usable 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 minimally 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. Additionally, 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.
============================== ============================== ============================== ============================== ================

I can sink my teeth into that

 

[CannaRed]

Thank you to all of those posting the papers, links and citations!
great reading material!

 

[delta9nxs]

Defoliation is standard practice in the cotton industry, as there are studies which show conclusively that higher quality cotton flowers are a direct result of defoliation.

this is chemically done solely at harvest primarily to get the cotton plant to drop leaves for easier mechanical harvesting with less trash. it also stops further growth and triggers uniform boll opening. it is not done to increase yield.

 

[delta9nxs]

I've participated in multiple threads about "defoliation". always the same results with nothing ever resolved to the satisfaction of the "real scientists" who demand cut and dried research papers, side by sides, and other formal scientific comparisons absolutely proving or disproving a technique they have never even tried.

these "i'm a real scientist and you are a bro-scientist" type want someone else to prove or disprove it for them. they have also forgotten that early man only had empirical results and that collective empirical data is just as valid as peer-reviewed research.

then we have hobby growers in small spaces growing small but beautiful plants showing their work claiming they got better results one way or the other. (imagine variables ramifying).

i think the first problem we have is the definition. what is defoliation? various dictionaries say it's a verb meaning "to remove leaves from a plant for commercial purposes, especially prematurely".

ok, i'll buy that.

there are thousands of variations depending on which plant, what it's being grown for, environmental conditions, and let's not forget lighting.

we have people here comparing cannabis to all kinds of plants. i think i remember sunflowers, tomatoes, and potatoes, and maybe some other plants that have absolutely nothing to do with this discussion.

but if we confine the discussion to cannabis i think we can make some progress.

and then further confine the discussion to indoors, which is where most people do commercial defoliation.

outdoors you thin the centers outward but are basically removing leaves that are already occluded. i don't think thinning plant centers applies so much indoors where fewer and fewer folks are growing large trees.

now, especially with leds, we have more and more flat canopies being presented to flat light arrays.

within the cannabis growing world, we have a huge range of genetics with a huge variance in morphology.

the pro grower should know which plants need more attention because of type and which ones don't.

i have grown 10' diameter plants indoors tree style and sea of green.

everything in between and all had different pruning requirements.

i just said pruning. and that is what it really is with cannabis.

i have experimented extensively with pruning and i can say that if you don't have a clear-cut reason to do it to a plant don't do it. you will probably hurt yield.

valid reasons to prune;

1. the plant stretches like a mofo and we all know this is not good under lights.

starting in early veg with a plant like this i will top it at about the seventh or eighth node one time. just the bare minimum tip.

letting it resume noticeable growth (usually a couple of days) and then begin removing the major fans on the main stem one or two at a time during veg but only as they become shaded. from the bottom up.

this puts the brakes on stem elongation above the node the fan was connected to. (see red/far red ratio and elongation response).

other than that i don't touch them until a week before flower. at that point, i rather radically remove all growth that will not see light.

then pretty much leave them alone.

2. the plant is a short, fat indica leaning plant with an extremely busy interior.

if you don't remove material strategically you will get a ball of larf with a thin veneer of decent flower but not much weight.

here i will not do much during early veg because these types usually are slower growing and removing much material slows them even more.

about a week from flower i will take most growth off the plant starting from the bottom up again. stripping not only the fans but also the shoots that are close to the main stem.

i leave just the tips of the main branches allowing maybe 4-5 inches of growth to remain.

3. most indoor plants fit into this category.

commercial growers recognize that, for maximum annual yield, they should choose from sativa/indica hybrid types that have similar growing characteristics, finishing times, etc.

these mostly require topping early veg again around the seventh or eighth node and then progressive fan removal on the main stem starting at the bottom.


you should do all this type of work to the plant at least a week before flowering giving the plant time to regrow and regain vigor from whatever you do to it.

don't touch them during stretch but then as you flower just a slow, steady, a few at a time. daily, removal of individual leaves blocking light to bud sights.

the last week of flower i go after major fans everywhere on the plant.

this allows more direct light to hit the flowers. they do plump while they finish.


in this discussion, no one has mentioned roots. what roots? the ones below the plant you are butchering up.

roots and shoots bootstrap each other. hormonal crosstalk.

so when you remove material from the aerial portions of the plant it responds by rapidly replacing the lost material to match root capability. taking off too much slows recovery speed.

but the right amount at the right time will produce more flower weight because the energy from the roots has nowhere else to go.

by judicious pruning you can steer the plant into growing more flower and less stem and leaf.


now we get to the discussion about ramification. we have talked about the plant reactions to a major fan leaf being removed. the fan leaf adaxial surface contains random cells that sense light quality in the 660-740 nm range. as these cells become occluded they send signals to the node it's attached to which then causes elongation of the stem section above it.

so removing that one leaf stops that one node from stretching that one stem section.

then what does it do? it grows another shoot site at a tighter interval than you would have gotten had you not removed that leaf.

shoot count increases flower count.

this effect is further enhanced by light but that's a different discussion.

this type of training should be done in veg before flowering giving the aerial portions time to regain vigor or you can end up with the same total weight of flower only all smaller. done right it will increase flower weight because of the roots.

i can hear the responses to this already. where is your research data? where is the proof? where are the references?

well, i don't have any.

but what i do have is 25 years of continuous cannabis growing not just for myself but for other folks as well. oh, and i get paid really well for it, too! i wonder why people are willing to pay me to teach them how to grow? i'm either a great con artist like donald trump or i just might have a proven history of high-yielding production.

i could spend a few hours looking up the references for you but i'm busy and don't really need to prove myself to anyone so i openly challenge anyone to refute the information i've put forth.

while you are wasting your time i will put up a few pics to demonstrate the effect of pruning done right.

have a nice day!

 

[Devoted2rolling]

they have also forgotten that early man only had empirical results and that collective empirical data is just as valid as peer-reviewed research.

That's called science.. The problem is this social trend amongst pot users/growers to only accept things that are official, and officiated by officials.

These people will suck dick for 6 hours every January 1st if the president institute a position that demands it,and Hallmark prints a National Dick Sucking Day card. For fucks sake.

 

[Chi13]

I've participated in multiple threads about "defoliation". always the same results with nothing ever resolved to the satisfaction of the "real scientists" who demand cut and dried research papers, side by sides, and other formal scientific comparisons absolutely proving or disproving a technique they have never even tried.

these "i'm a real scientist and you are a bro-scientist" type want someone else to prove or disprove it for them. they have also forgotten that early man only had empirical results and that collective empirical data is just as valid as peer-reviewed research.

then we have hobby growers in small spaces growing small but beautiful plants showing their work claiming they got better results one way or the other. (imagine variables ramifying).

i think the first problem we have is the definition. what is defoliation? various dictionaries say it's a verb meaning "to remove leaves from a plant for commercial purposes, especially prematurely".

ok, i'll buy that.

there are thousands of variations depending on which plant, what it's being grown for, environmental conditions, and let's not forget lighting.

we have people here comparing cannabis to all kinds of plants. i think i remember sunflowers, tomatoes, and potatoes, and maybe some other plants that have absolutely nothing to do with this discussion.

but if we confine the discussion to cannabis i think we can make some progress.

and then further confine the discussion to indoors, which is where most people do commercial defoliation.

outdoors you thin the centers outward but are basically removing leaves that are already occluded. i don't think thinning plant centers applies so much indoors where fewer and fewer folks are growing large trees.

now, especially with leds, we have more and more flat canopies being presented to flat light arrays.

within the cannabis growing world, we have a huge range of genetics with a huge variance in morphology.

the pro grower should know which plants need more attention because of type and which ones don't.

i have grown 10' diameter plants indoors tree style and sea of green.

everything in between and all had different pruning requirements.

i just said pruning. and that is what it really is with cannabis.

i have experimented extensively with pruning and i can say that if you don't have a clear-cut reason to do it to a plant don't do it. you will probably hurt yield.

valid reasons to prune;

1. the plant stretches like a mofo and we all know this is not good under lights.

starting in early veg with a plant like this i will top it at about the seventh or eighth node one time. just the bare minimum tip.

letting it resume noticeable growth (usually a couple of days) and then begin removing the major fans on the main stem one or two at a time during veg but only as they become shaded. from the bottom up.

this puts the brakes on stem elongation above the node the fan was connected to. (see red/far red ratio and elongation response).

other than that i don't touch them until a week before flower. at that point, i rather radically remove all growth that will not see light.

then pretty much leave them alone.

2. the plant is a short, fat indica leaning plant with an extremely busy interior.

if you don't remove material strategically you will get a ball of larf with a thin veneer of decent flower but not much weight.

here i will not do much during early veg because these types usually are slower growing and removing much material slows them even more.

about a week from flower i will take most growth off the plant starting from the bottom up again. stripping not only the fans but also the shoots that are close to the main stem.

i leave just the tips of the main branches allowing maybe 4-5 inches of growth to remain.

3. most indoor plants fit into this category.

commercial growers recognize that, for maximum annual yield, they should choose from sativa/indica hybrid types that have similar growing characteristics, finishing times, etc.

these mostly require topping early veg again around the seventh or eighth node and then progressive fan removal on the main stem starting at the bottom.


you should do all this type of work to the plant at least a week before flowering giving the plant time to regrow and regain vigor from whatever you do to it.

don't touch them during stretch but then as you flower just a slow, steady, a few at a time. daily, removal of individual leaves blocking light to bud sights.

the last week of flower i go after major fans everywhere on the plant.

this allows more direct light to hit the flowers. they do plump while they finish.


in this discussion, no one has mentioned roots. what roots? the ones below the plant you are butchering up.

roots and shoots bootstrap each other. hormonal crosstalk.

so when you remove material from the aerial portions of the plant it responds by rapidly replacing the lost material to match root capability. taking off too much slows recovery speed.

but the right amount at the right time will produce more flower weight because the energy from the roots has nowhere else to go.

by judicious pruning you can steer the plant into growing more flower and less stem and leaf.


now we get to the discussion about ramification. we have talked about the plant reactions to a major fan leaf being removed. the fan leaf adaxial surface contains random cells that sense light quality in the 660-740 nm range. as these cells become occluded they send signals to the node it's attached to which then causes elongation of the stem section above it.

so removing that one leaf stops that one node from stretching that one stem section.

then what does it do? it grows another shoot site at a tighter interval than you would have gotten had you not removed that leaf.

shoot count increases flower count.

this effect is further enhanced by light but that's a different discussion.

this type of training should be done in veg before flowering giving the aerial portions time to regain vigor or you can end up with the same total weight of flower only all smaller. done right it will increase flower weight because of the roots.

i can hear the responses to this already. where is your research data? where is the proof? where are the references?

well, i don't have any.

but what i do have is 25 years of continuous cannabis growing not just for myself but for other folks as well. oh, and i get paid really well for it, too! i wonder why people are willing to pay me to teach them how to grow? i'm either a great con artist like donald trump or i just might have a proven history of high-yielding production.

i could spend a few hours looking up the references for you but i'm busy and don't really need to prove myself to anyone so i openly challenge anyone to refute the information i've put forth.

while you are wasting your time i will put up a few pics to demonstrate the effect of pruning done right.

have a nice day!

A couple of points.

I really don't get the anti-science that some of post. You say "they have also forgotten that early man only had empirical results and that collective empirical data is just as valid as peer-reviewed research". Early man used to do all sorts of practices to effect their world that were based in superstition. I don't think sacrificing to a sun god, for example, will make your cannabis grow better, and I doubt you do either. When I was first starting to grow there were all sorts of things I learned from hippie growers. One was to pull the plant out at harvest and put roots straight into boiling water so that the resin would flow to buds. People swore that worked.
That's not to say early man knew nothing, they certainly did. But some practices obviously made no sense. They were also no doubt acutely aware of their natural world, and no doubt learned a lot through trial and error. The problem with that approach is that it doesn't account for variables, and flukes. If I decide to make a sacrifice to the rain god, and it rains, I might conclude that works. Maybe I do this a few times and get the same result? However to a modern person that makes little sense. Proper science on the other hand would takes account of variables and flukes . It requires a control, and for experiments to repeated, so that over time it can be concluded that various things work, or don't.

I do prune plants btw, the odd lower branches, but I do not remove leaves until they are almost dead. I see you mention leaf occlusion. I just want to make the point that leaves that do not get direct light still get diffused light, and this adds to the overall plant energy (solar panel analogy). There seems to be a misconception that if you don't get direct light, then it is worthless. Leaves and buds still grow without direct light, just maybe not quite as well.

As I said to other growers, just because you have great defoliated plants, does not mean they wouldn't be better if you had left the leaves on. Taking leaves off makes the buds more visible and they still grow, so people assume that it works? Unless you do an experiment you simply don't know. Nice plants you certainly have.

I can't refute your information, but neither can you show that it works. All you can show is that you grow good plants. You can't show that you grow better plants compared to identical clones that were not defoliated.

 

[delta9nxs]

bushels of leaves were pulled from these plants. lots of lower limbs were removed. averaged 3 per light. some like the wreckage (pointy flowers) yielded 3.5. had an iranian c-99 cross that hit 3.9 lbs of dense flower.

these were in oregon 3 yrs ago. my last effort using hps. please notice that there is only one stem under each canopy.

i guess i fucked up! i wonder how much more i could have gotten if i hadn't removed any leaves?

 

[delta9nxs]

i have received a request to show the source of these pics so here it is.

https://www.icmag.com/forum/marijua...-hydro/335793-something-wicked-this-way-comes

 

[Hammerhead]

Yield is a direct cause of the genetics grown not whether you pruned your plants. It's clear some have misused the word Defoliation.. That is not what most are doing. We call this pruning.

 

[Donald Mallard]

agreed hammer ,
i see plenty of shade leaf left on the above pictures ,
not exactly my idea of defoliation , or denuding ,
seems to be varying degrees of this method ,
and there is no secret that some pruning can assist in getting as much as one can from their plants ,
but as you say , you can never do better than genetics allow,
you are just getting the most from them ...

 

[delta9nxs]

hello fellas! yes, the word defoliation sounds like you are raping mother nature!

i have done total and complete fan leaf removal experimentally leaving only the shoots. i don't recommend this practice as it will severely stall the plant.

if you allow enough time for recovery it will rebound and grow with more actual bud sites because of the total loss of the sensory apparatus that sends signals to elongate.

but if you flower it before the total recovery occurs you can end up with a bunch of smalls that, in aggregate, will probably about equal the normal bud weight the roots are capable of supporting anyway.

flowering after full recovery may reward you with more flower weight. i say may because i think it's strain dependent.

in a commercial scenario you don't have the overhead and labor resources to wait for plants to "recover" from intentional damage.

so i don't know any commercial grower on any scale that does radical defoliation. but i also don't know any that don't prune either, indoors or out.

some plants just don't need any help. i had a sweet tooth #4 that didn't when grown tree-style bare hps bulbs.

i think i've got a pic or two of it somewhere. this plant just shaped and grew like mad with very little help other than support. very little larf. in retrospect i think i should have cleaned out the interior a little.

 

[Switcher56]

If you aren't stuck on a schedule e.g churn and burn.

if you allow enough time for recovery it will rebound and grow with more actual bud sites because of the total loss of the sensory apparatus that sends signals to elongate.

Affirmative! I have said it before and I am going to say it again. It is whatever works best, in "your" environment. Opinions are like........
That being said, I am not bound by a schedule. Manifolding for me has kept my plants under 30" and has increased my yields. Currently growing Rg and Kl. Although I manifolded for 8 tops, I have 15, 16 and 11 respectively. 11 is King Louis. King Louis (Indica) does not seem to like the practice. I will know after harvest but I have made a note of it. My NL and LA Conf run (Indicas) 66, 74, 63, 71g. Not to shabby... for a 3x3 (0.98g/w) I am happy and at the end, isn't that what really counts?

 

[CannaRed]

I listened to this podcasts that discuses defoil.
he mentioned the work of Dr Alice Justice that says if a lower leaf is getting less than 200 micromoles it's a drain on the plant.
This was the same study I read over a year ago, but I couldn't remember what number they said.

Figured this was best place for this link.

https://growcastpodcast.libsyn.com/...he-science-behind-legacy-grows-with-david-k-0
​​​​​​

 

[Switcher56]

Great commercial

 

[CannaRed]

Great commercial

Sorry, I did know all that was going to show up by posting the link. Lol. That is a bit much

 

[944s2]

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

I’m with.Verdant,,,
After multi topping then I remove fans that are blocking light or in bloom when there using up the bottom leafs and have faded an dropping off,,,,