can anyone exsplain why/how defoling increases yeilds?

[tyler_ hobbyist]

How do u increase yields by cutting off leafs that converts light energy to growth?

[JohnC]

I think the general idea is that by defoliating you expose more bud sites to light, which in turn induces them to grow. More buds that grow = higher yields.

The trick is not to go crazy on the defoliation; too much defoliation can stress out a plant, increasing chances for problems as a result.

[GanjaGed]

How I see it


There's a couple of principles at work with Defol. and it matters if it's the main training scheme or an added one.

Defol in a way simulates nature where non-lethal damage invigorates the plant making it stronger and growing.

As I see it, the real purpose of Defol is to make a 3d canopy rather than a flat one. The idea being that with the air and light that the lower bud sites get exposed to will become grade A/B buds rather than larf. With the plant open like that you also reduce the chance for mold.

I would expect that it also acts as a semi-pest prevention measure as in an aggressive Defol program leaves aren't left long enough to become colonized. That's just a guess, but seems reasonable to me.

It seems like a good way to manage vertical grow space since you can add the room below the canopy normally lollipoped or barren because of light not penetrating.

[DrPhoton]

I have looked into the physiology of it, read all the studys and any other information on the subject. It appears the only process to have any involvement is nutrient translocation. The stress induced by the removal of leaves could induce the movement of nutrients from one location to another. However controlled studys show such manipulation to barely make a difference and most plant species show a negative impact with more than 30 percent removal. Also i have seen no controlled side by side showing an improvement. In fact i can recall one person who attempted a comparison only to find that neither plant was any different.

Theres also the possibility for the removal of older leaves to have an impact, however this would be specific defoliation and not the traditional method.

I am very interested in finding more information on this but currently its an unproven method for me and holds no scientific structure.

[GanjaGed]

I don't think anything was mixed on purpose, and I don't even know if accidentally, but for myself I do have a hard time differentiating between the twp plants and the training difference. I would thinks it's more an illusion of a picture and in actual view the difference is quite noticeable.

[DrPhoton]

Yes i had a look through the thread, clearly the heavy defol has caught up. This may ruin the defol experiment for the flowering stage however as the regrowth has now outbalanced the leaf count.

[Burny]

Both of those plants were defoliated. Just one more than the other. It is really not even relevant. Needed one with no defoliation and the same training methods done to both.

[furrysparkle]

There are 3 things that buds need to gain weight;

Light

Wind

Nutrients


By removing the leaves the block either light or a breeze the bud recognizes the conditions needed to get a pollen particle, thus will grow larger in attempting to make a seed. There is also less plant matter to soak up nutrients as well, leaves are nutrient tanks to protect the plant through drought and to provide for the buds when nutrients are scant.

Thus enters the gardener who recognized this ingenious way to ensure the nutes you put in go straight to the buds and the buds know to use them to try to make seeds for the next generation.

Although we all know an unpollenated plant just makes buds!

[DrPhoton]

Although environmental stimuli influences behavior characteristics, these are mostly minimal. Sexual expression is brought on by photoperiodism and genetics, without these the initiation process cannot start. As the development of sexual expression continues, it depends on basic principles of growth from generic materials provided by the plants photosynthesis process. As the flower acts like a true "sink" it will initially use most nutrients provided to develop its flowers.
Light, carbon dioxide and minerals are the requirements for plant development processes. Exposing the flower has very little impact as the leaves have very little photosynthetic capacity compared to the more mature leaves.

[Weed Pharma]

Also, defoliation is usually in conjuction with breaking the apical dominance and creating many main colas of equal size- rather than one large cola-
You get many colas, with greater overall weight/denisty as they tend to be the same distance to the light
Not all strains defoliate well.
It's still a controversial subject, but once you get good results- it's very hard to not defoliate plants( in some form or another)

[furrysparkle]

This conjunction technique is referred to as topping. For @tyler_hobbyist

[tyler_ hobbyist]

Thank you everyone I appricate all ur input

[desertdan]

I have read this only works indoors and produces less yield outdoors. Why?

[DrPhoton]

The only variable i see is the sun, i cannot work out why this would be different however. I will think on it.

[Weed Pharma]

When a plant is outdoors- the sun travels across the sky and provides light to all parts of the plant-
Indoors the light is stationary and directly above- so defoliation is effective in getting more light to more buds.

[DrPhoton]

This crossed my mind but im not convinced, all you would be doing is changing the area where light is being delivered. You would not gain any more surface area if the canopy is already filled. The amount of photons leaving the light source that reaches the plant, still ends up being utilized, regardless where it lands.
Theres also the issue of the shade leaf being exposed, leafs that are shaded are biologically structured for specific light levels. This is the prime reason why moving plants from indoors to outdoors can be stressfull as their ability to process light is different.

[tyler_ hobbyist]

I personaly havnt seen much of a difference with defoling so thats why I ask the only difference iv seen is maybe 0.5-1 more of a gram per bud if bud sites are clear of leaves and with some strains I havnt noticed anything so I wounder how it actualy works

[desertdan]

I have seen defoliated plants outdoors stunted

[PRIMO]

I have seen indoor plants explode with new growth after a good defolling

[tyler_ hobbyist]

I have seen this as well but does that really help the plant because no it uses energy to remake leaves instead of makeing buds

[D.A.A.S.69]

I have witnessed explosive growth after hard core defoliation on many,many pot plants. Different strains vary with defoliating, some like it alot, some not so much. Just don't take to much green. It will help with your yield, at least it always has helped with mine.

[Weed Pharma]

It has gone both ways for me- here is a side by side that simply didn't work. http://forum.growweedeasy.com/forum/...oe-og-kush-50g -It was an anomaly for my grows.

I attributed it to a strain (sativa) that doesn't respond well, as I have had great results when defoliating.

Mostly I use LST/defoliation as an aid to obtain the best canopy when I grow several different strains together!

[Burny]

Where is any evidence that it actually works?

[tyler_ hobbyist]

I would love to see this as well side by sides arnt always good because different strains act differenly to stress so a more accurate peace of evidence would be nice if anyone has found any saying ya or nay

[GanjaGed]

There's an internet full of studies... again nothing with cannabis directly, but the usefulness of defoliation on plants abounds.

The 2 things that limit study on cannabis is well, prohibition makes study difficult, and Summer Annuals like Cannabis are more difficult in a test environment than grasses and perennials. These are just 3 that a simple google search will bring up.
Abstract

1 Competition is considered to be one of the main biotic factors shaping plant communities. Experiments on the role of mycorrhizal symbiosis in plant competition have reported conflicting results. 2 We studied the effect of arbuscular mycorrhizal symbiosis on below-ground interactions between seedlings and established adult plants in a system where plants compete for below-ground resources. In this glasshouse experiment, seedlings of Gnaphalium norvegicum were grown with and without an arbuscular mycorrhizal fungus, in the presence and absence of a large conspecific adult plant. The ability of adult plants to support the fungus was modified by defoliating 0%, 50% or 75% of its leaf area. 3 We found that mycorrhiza increased below-ground competitive intensity. The mycorrhizal benefit to the seedlings was low in the vicinity of non-defoliated adult plants, but increased with increasing defoliation intensity of the adult plant. This was mirrored by reductions in mycorrhizal benefit that adult plants gained at the highest level of defoliation. 4 These results emphasize the importance of below-ground competition during seedling establishment and show that competition for mycorrhiza-mediated resources may be an important factor underlying seedling establishment in nutrient-poor systems. Defoliation of neighbours can increase the beneficial effect of mycorrhizae to seedlings establishing in the vicinity of larger plants, suggesting that grazing or mowing may improve seedling establishment by decreasing below-ground competition.

...

Results for total carbohydrates mirrored those for concentration, but were not as significant. Our findings were consistent with the idea that faster growing species respond more rapidly than slower growers to defoliation, through changes in carbohydrate pool concentrations. Growth rate as an indicator of life-history and ecological strategy may therefore be key to understanding post-defoliation recovery and storage strategies.

...

ABSTRACT

Mustard (Brassica juncea L.) is characterized by a large number of leaves in the lower layers. These leaves are poorly illuminated, remain below the light compensation point and abscise at maturity. The effects of removing 50 % of all leaves taken from the lower half of the plant at 40 (pre-flowering) or 60 (post-flowering) days after sowing (DAS) were studied on photosynthesis and growth at 80 DAS and on yield at harvest. A comparison of stomatal and mesophyll effects on photosynthesis upon removal of such leaves was also made. Defoliation at 40 DAS resulted in a higher rate of photosynthesis (P_N), growth and yield compared to defoliation at 60 DAS or the no defoliation control. The non-significant variation in stomatal limitation (I_S), increased activity of carbonic anhydrase (CA) and constant C_i/C_a ratio in defoliated plants suggest that the main effect on P_N was through enhanced mesophyll rather than stomatal effects. Defoliation at 40 DAS caused the greatest emergence of new leaves with rapid growth, which contributed to maximum leaf area as well as leaf and plant dry masses. The favourable effects of defoliation at 40 DAS on photosynthesis and growth were reflected by seed yield and attributing parameters.

[GanjaGed]

Well now that's where the controversy lay, lol.

It honestly appears to be a plant by plant (species) situation. Works for this but not for that. In general it seems usually good for grass type plants, terrible for tubers and hit or miss for others. And many are looking at it from a damage perspective from natural problems rather than a system of training.

And like so many things it depends on what one is trying to accomplish, It may not increase yields in and of itself, but on an individual level where one is fighting space being able to utilize say 8" of otherwise "dead" space could easily increase yield even if the defoliation results in no, or even a small decrease in "normal" plant yield.

I would think it also depends on the light, it seems you'd have to have a light with good penetration potential to take full advantage.

[DrPhoton]

Actually i have read all the major studies on defoliation for many species of plants, as i have described previously, they all come to the same conclusion.
When it comes to the management of the plant for structural or environment reasons, this is really classified as plant training or pruning. Especially selective removal of leaves is not really defoliating.

I have actually spent the last couple of days on the subject, looking at practically all material relating to defoliation. I thought i might even find some reason that could convince myself of the possibility. However it went completely in the other direction. I will likely do a follow up post of my research.

[GanjaGed]

I yield to the man who has read every major report on the subject. I personally haven't read them all. Looking forward to your summary.

[tyler_ hobbyist]

Yes me 2 I cant wait to learn more