Defoliation criteria - 200 mmol/m2/s

Just listened to a Growcast episode from 7/18.

The guest mentioned that there is a study showing that an effective criteria for determining whether to defoliate a particular leaf is 200mmol/m2/s. This is because below this level it takes more energy to maintain that leaf than the leaf provides back to the plant.

Just wondering if anyone has seen this study and where I could score a read - sounds like a very interesting idea. Thanks in advance.

 

[2budz]

 

[2budz]

That plant is not typical. I don’t strip vegging plants. But she was so leafy some of her inner/lower branches were growing down looking for light. I figured I’d give that a shot and see what happens.

 

[420autoflower]

View attachment 1511835

Nice schwazzing job @2budz

 

[Delps8]

nice work putting all this together.
This summer I learned a bit about this, I think:

Had/have an ultimate that was fed perfectly and very controlled, when I dropped N too early, but just a little, so I could observe the move of N at this stage very nicely. And what I saw was, that the yellowing happened at the biggest (not the oldest or first ones) lower fanleaves, that grow on the stem directly. Those big ones got drained first.
And it literally went from leaf to leaf. You get a clue how you feed movable nutritients from them and have some time to react till it spreads to other leaves. As long as you feed well, you won't need other leaves as storage and can clean out the canopy for more light. Significant role..yes indeed, but as we are not in nature and can control the feed, the role may be" just" a "warrant canary". By doublequoting "just" I want to stress the importance of watching these leaves together with the new growth to keep the plant healthy. Having them there to watch them is good value!
Leaving them and defoiliating the smaller rest (ref Dr Justice , only if I think needed) in the shadows is what I will do the next runs - now I have some numbers for the light penetration to add to that, thanks!

Interesting experiment. It must have been interesting to watch the leaves change in sequence. That might have been part of a natural process, as described below.

Bugbee details the movement of either K or P (I think it's K) from the lower leaves to flowers. Their description is that cannabis "panics" when it comes to building flowers and it moves up to 10x as much K as it needed by the flower because it's thinking that it's got to create nutrient rich seeds.

Perhaps cannabis and/or other flowering do that simply as a matter of course. The sticking point is "feeding well" - looking at elemental analysis for different formulations of cannabis nutes, what struck be is the very broad range of values. There are some nutes where the ratios are quite important but, as long as growers long stick to those ratios, the PPM levels can vary significantly and cannabis just trundles along. Bugbee, and I guess the rest of the ag industry, is grappling with growers using too much phosphorus. Apparently growers start with high levels of P and then add "bloom boosters" resulting in far more P than is needed. He illustrates how little P is needed - something like 15 to 30 PPM is all that's needed.

"Leaving them and defoiliating the smaller rest (ref Dr Justice , only if I think needed) in the shadows is what I will do the next runs - now I have some numbers for the light penetration to add to that, thanks!"
You're welcome!

 

[Delps8]

Best and most thorough defoliation comparison I’ve ever seen.

The attached document might add something to the discussion.

 

[Delps8]

I’ve tried many times without the defoliation and always end up with half of it being larf.
I can consistently pull 2 pounds of primo bud out of a 4x2” tent using only 300 watts and 4-6 pounds out of a 5x5” tent running only 600 watts.
It’s a

Here are a few tents I just harvested a couple weeks ago

2x2” tent
View attachment 1511791

2x4” tent
View attachment 1511793

5x5” tent
View attachment 1511792

Here are 2 current grows

Autoseeds.com testers
View attachment 1511794

Black Strap
View attachment 1511796

What lights are you using and what was your lighting plan?

 

[Tom Bombadil]

Leaves blocking
1) growth tips during stretch
2) maturing bud sites
get yanked.
Im lazier than all of you on your worst day COMBINED! :smoking:

 

[Death The Cultivator]

The attached document might add something to the discussion.

The double prune mentioned in the article is what I do personally and commercially at day 10/21 of flower. Every branch and leaf that does not reach the canopy or thinner than a pencil must go leading to zero larf and quality buds. Even for mother plants it's in two stages to improve hormone distribution when it comes time to cut clones, 1st prune is the lower 1/3 and the second prune is topping to double the amount of clones and create an even canopy. I'm also a firm believer in minimal stress lol.

Depending on the overall size, structure, and method plants in flower would be lightly defoliated mainly across the main stems in the "crotch" area of the plant because air circulation was minimal in those areas and would become breeding grounds for pest or mold.

Lower veg times for overall less biomass but higher planting densities reduced time to harvest, labor in regards to removing biomass, and increased the speed of harvest while improving yield. Shorter canopies are easier to manage and require far less pruning than 6ft tall plants that even if you strip all the leaves, lighting will only penetrate so deep with regards to the inverse square law.

 

[CannabisMingus]

at day 10/21 of flower

Hey @Death The Cultivator I am not exactly sure what you mean here. Can you clarify? Thanks!

 

[Death The Cultivator]

Hey @Death The Cultivator I am not exactly sure what you mean here. Can you clarify? Thanks!

Spreading the bottom prune out over two different days. Day 10, remove branches that do not reach the canopy. Day 21, remove thin growth(smaller than a pencil) and leaves in the crotch of the plant.