Summary of Cannabis Defoliation Side-by-Side Experiment

Last updated Feb 09, 2024

by Nebula Haze

The results are in! Have you ever heard of the cannabis flowering stage defoliation technique? It involves strategically removing leaves when the buds are first forming on marijuana plants. The goal is to expose buds to plenty of light and air, which seems to increase overall yields and bud quality on your cannabis plants.

I love doing side-by-side cannabis experiments because I always end up with a ton of awesome weed lol

This grow journal features a 300W LED grow light that’s been discontinued. This is the LED grow light I recommend as a replacement (excellent results with cannabis yields and bud quality): Mars Hydro SP3000

But does defoliation work?

In this grow journal we discovered that, at least in this first test, the defoliated cannabis plants produced…

  • Bigger yields
  • More THC in buds (details below)
  • Higher quality bud (no larf or airy buds; all buds well developed)

Here’s a quick summary of the final results. The defoliated clones produced bigger yields, more THC, and buds were denser (“tight”).

This article contains highlights from the side-by-side cannabis defoliation experiment plus the results. Here is the full grow journal with weekly entries from beginning to end for those who want to get a week-by-week breakdown.

Setup & Supplies (one set for each tent)

Click here for a full breakdown of this setup

Wildberry

Runtz

Platinum Cookies

Experiment explanation

Clones were grown in identical conditions until the day I put the grow lights on a 12/12 light schedule to initiate the flowering stage. That is when the experiment officially began.

Natural Tent did not receive any defoliation during the flowering stage.

Defoliation Tent received strategic defoliation in the flowering stage. I removed most leaves from the plant on the first day of 12/12 and once more about 3 weeks later.

Let’s skip to the beginning of the flowering stage after the first defoliation.

 

Initiate 12/12 and First Defoliation

This is just before I initiate the flowering stage with a 12/12 light schedule and do the first defoliation. At this point, these plants have been grown in identical conditions.

The “natural tent” (blue tags) just before the switch to 12/12. This is the “control” tent. These plants don’t get touched between now and harvest. All they receive is nutrient water and light.

Here is the “defoliation tent” just before the plants get their first defoliation. As you can see, the plants look almost exactly the same because they are clones and have been grown in identical conditions until this point.

Week 0 Defoliation Summary: Lollipop and defoliate plants (I did this the day I switched to 12/12 to initiate the flowering stage)

  • Lollipop = remove all leaves at the bottom part of the plant which don’t get light.
  • Make sure there are 8 main branches for each plant (cut away the smallest ones)
  • Defoliate =
    • Remove all fan leaves bigger than a hand.
    • Remove leaves with stems longer than 3 cm
    • Note: Make sure to keep at least a few leaves at the top of each main branch. You don’t want to completely strip the main branches so there are still leaves at the top to power the growth of buds.

Here is the “defoliation tent” after getting defoliated and lollipopped according to the instructions above.

The defoliation tent will receive one more plucking session in 3 weeks and then all the plants will be left alone until harvest. I wanted to make it so that people could follow along if they wished to, so I kept the training really simple and straightforward without a grower having to make any judgment calls.

Here are both the tents the next day so you can see the two sets of clones side-by-side.

The plants receive only nutrient water and light for the next 3 weeks.

Second Defoliation (3 weeks since 12/12)

Wow, what a difference in the last 3 weeks! The plants have just been receiving water and nutrients and no other care. Let’s check out how they look.

Here’s the natural tent. It’s a jungle in there. These clones had a surprisingly big flowering stretch (more than doubled in height), which I attribute to the deep red spectrum of the HLG 300 R-spec LEDs.

Here’s the defoliated tent. The lower parts seem a bit more exposed than in the natural tent, but overall the clones look remarkably similar so far. They are about to receive their second and final defoliation.

Week 3 Defoliation Summary: Defoliate one more time.

  • Remove all fan leaves with stems longer than 3 cm
  • From then on, only remove leaves if they’re covering a bud site or if the plant starts getting so bushy through the middle and bottom that light isn’t making it to the floor

Here are both sets of plants after the second defoliation. Notice on the bottom of the undefolaited plants are in total darkness. However, the plants in the defoliated tent get light all the way to the bottom.

The idea now is to leave the plants alone until harvest. Let’s see what those two defoliation sessions did for us compared to the control tent.

Week 8 of the flowering stage

It’s now been 5 more weeks and I’ve noticed that the two clones on the right in each tent look ready to harvest now. However, the Platinum Cookies plant all the way on the left needs a few more weeks before the buds look ready to harvest.

Here’s the natural tent. I’ve noticed the buds at the bottom (which are in total shadow when the tent is closed) appear bleached and are not developing normally at all. Without any exposure to light, the plant appears to be “giving up” on all those leaves and buds. This is going to become relevant later.

Here’s the defoliated tent. One of the most significant differences I’ve noticed between the tents is that the buds on the defoliated plants are green all the way to the base of the plant. Since every bud is getting access to light, even the lower and smaller ones are developing normally.

Here is what it looked like to harvest the two plants on the right in each tent. I used one tent to dry all the buds. I made sure to carefully label all the buds because I will be doing lab tests.

I moved the remaining Platinum Cookies plants together since the other tent was being occupied by drying. I think it’s pretty easy to see which plant is which. It’s neat to see the natural and defoliated clone next to each other like this.

The two Platinum Cookies clones need a few weeks to finish maturing. The clone on the left was defoliated, while the clone on the right was from the natural tent.

Final Harvest Day

The two Platinum Cookies turned purple as the buds matured. Here are the two Platinum Cookies clones just before harvest.

Harvest time!

Buds hanging to dry (wow, just two plants!)

 

What are the final results?

Weigh-in and lab results are in! The HLG 300 R-Spec uses 270W of electricity, so that’s what I’m using to calculate grams/watt.

Natural tent

  • Yields: 274.43 g (9.68 oz) – about 1 gram/watt
    • Premium buds from top of plant: 188.14 g (6.64 oz)
    • Bleached buds from the bottom of plant: 86.29 g (3.04 oz)
  • Terpenes: 12.91 mg/g average
  • 22.09% THC (Average)
    • Wildberry: 21.72% THC
    • Runtz: 19.16% THC
    • Platinum Cookies: 25.38% THC

Defoliation tent

  • Yields: 298.68 g (10.54 oz) – about 1.1 gram/watt
  • Average Terpenes: 12.74 mg/g
  • 23.45% THC (Average)
    • Wildberry: 23.38% THC
    • Runtz: 20.01% THC
    • Platinum Cookies: 26.96% THC

Wildberry – Defoliated

Wildberry – Natural

Runtz – Defoliated

Runtz – Natural

Platinum Cookies (buds turned completely purple!) – Defoliated

Platinum Cookies – Natural

Note: The Platinum Cookies is the crowd favorite in smoke tests from this grow. Buds are smooth and potent.

Final Thoughts on Flowering Stage Defoliation

So, what do I think about flowering stage defoliation after this test? In many ways, it confirmed what I already suspected. Defoliation seems to increase yields and improve the overall quality/tightness of buds. I had heard growers say that defoliation might increase THC, but it was still a surprise to see that play out in the results for all 3 clones. If all 3 clones produced higher THC in the defoliation tent, that’s not definitive but it is pretty good evidence supporting the idea that defoliation may increase THC percentage.

Defoliation tent was the clear winner in my mind.

  • Higher yields
  • Higher THC
  • Higher quality buds

But why/how does defoliation work? I don’t know for certain, but here is my ideas so far

  • Without as many leaves, the buds get more exposure to direct light, causing those buds to fatten more
  • Defoliation removes leaves in shadow and buds that will never develop, so the plant can put all energy towards developing the best buds.
  • What’s causing the higher levels of THC? My two theories so far (could be a combination of both):
    • Plants that get brighter light produce higher levels of THC, and buds get more light when plants are defoliated
    • Defoliation stresses the plant, and the stress response is what increases THC

What’s next?

It seems clear to me that defoliation works to increase yields and bud quality, at least in this setup with coco and nutrients in the water. What I’d like to investigate more is what exactly is causing the higher levels of THC. Stay tuned to learn about my next experiment (I’ll be talking about it in our weekly Sunday newsletter and get feedback on what you want to see next).

I also may repeat the experiment using “just add water” super soil because I suspect defoliation would be less effective and may even reduce yields. That’s because removing leaves also removes a lot of the nutrients stored in the plant. With coco like this grow journal, I’m constantly adding new nutrients in the water so the plant always has as much as it wants. However, when you’re not adding nutrients to the water, there’s a limited amount in the soil. Therefore, I think it may actually reduce yields overall to defoliate because the plant will run out of nutrients in the crucial flowering stage.

Curious about the HLG LEDs? For those interested in learning more about the LEDs I used in this grow journal (which produced outstanding weed), here’s a complete review of the HLG 300 R-Spec grow light.

Platinum Cookies bud at day 38 of the flowering stage. This strain ended up being the highest-yielding as well as the crowd favorite in smoke reports!

 

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