Introduction to Defoliation
What is defoliation?
The point of defoliation is to “hack” your plant’s natural processes in the early part of the flowering stage to cause it to grow its buds and colas differently. There is some discussion whether defoliation is actually helpful or not but in our opinion and experience it does indeed help the plant direct energy to areas producing buds. In this article we’ll take a look at how to defoliate in a gentle way—of course you could go very far and defoliate the plant until it is bare but only do this if you are confident in what you are doing.
What is extreme defoliation?
Extreme defoliation refers to the aggressive and extensive removal of a significant portion of a cannabis plant’s foliage. This practice goes well beyond what would be considered standard or moderate leaf trimming. While there is no precise definition of the threshold for “extreme,” it typically involves stripping away a substantial percentage of the plant’s leaves, often up to 50% or more.
Benefits of trimming fan leaves during vegetative stage
- Improved light penetration – Removing select fan leaves allows more light to reach the lower canopy and growth sites, promoting better development of lower branches and budsites.
- Better airflow – Trimming opens up the canopy for increased airflow, which helps prevent moisture buildup and potential mold or mildew issues.
- Focused energy distribution – By removing some fan leaves, the plant can divert more energy towards desired budsite development rather than maintaining excessive foliage.
Defoliation During Veg
Topping should be initiated when the plant has developed 5 or 6 total nodes. Topping involves cutting the main branch immediately after a new node, allowing the two branches emerging from that node site to receive more energy and become stronger. This encourages the plant to grow more horizontally, resulting in a “bushier” appearance.
Plants should receive a thorough trimming approximately 4 to 8 weeks after the seed is planted. At this point, topping has created numerous new node points and encouraged stronger branch development. However, there will also be smaller leaves and branches within and beneath the canopy that consume energy without producing buds or capturing light. These leaves and small stems within and beneath the canopy should be pruned away. It is recommended to prune the plants every 2 weeks until about 1 week before transitioning to the flowering stage. To determine which leaves to remove, any single fan leaf that has its light blocked by two or more leaves above it should be pruned.
Defoliation During Flowering Stage
Flowering defoliation is usually a little more dramatic than Vegetative defoliation but in order for us to defoliate correctly during Flowering, we first should cut away any growth tips, small leaves, or parts of the plant that aren’t getting light before we enter Flowering – right before. If you want to get the best results, you can try “lollipopping” your plants, which means removing all the leaves below the point the light reaches – the name “lollipop” comes from the fact that your buds look like they are candy on sticks when you’re finished pruning during flower.
You can also prune away leaves higher up on the plant and have the growth focused solely on the buds – the technique is a little more advanced because you might remove some bud sites along the way so be careful not to damage those bud sites. Look carefully at where you’re going to prune and look for signs of bud sites and then remove the stems slightly above that point. You can either pinch or cut off smaller growths, whichever you feel most comfortable doing.
So there are three different times we recommend defoliating during Flower:
- Right before you switch to 12/12
- Once between the beginning of Flower and the 3-week mark
- 3 weeks after beginning flower is the last time you’ll want to defoliate
After 3 weeks you will also want to remove leaves that cover buds and bud sites but other than that you should avoid defoliating any further. Your plants should be ready in about 7 weeks!
What happens if you remove all fan leaves during flowering?
Reduced Photosynthesis: As fan leaves are the primary sites for photosynthesis, where the plant converts light energy into sugars and carbohydrates essential for growth and bud development, removing all fan leaves would severely limit the plant’s ability to photosynthesize, potentially starving it of the energy needed to produce healthy buds.
Stress and Stunted Growth: Removing all foliage would cause extreme stress to the plant, disrupting its natural growth processes and potentially stunting its development. Without leaves to capture sunlight and produce energy, the plant may struggle to recover and continue flowering.
Nutrient Imbalance: Fan leaves also play a role in nutrient storage and distribution throughout the plant. Consequently, removing them could disrupt the balance of nutrients, leading to deficiencies or toxicities that further harm the plant’s health and development.
When to remove fan leaves during veg?
A study by Vanhove et al. (2011) on tomato plants showed that removing 50% of the fan leaves from the bottom third of the plant at 4 weeks after transplanting resulted in a 25% increase in light interception in the lower canopy without significantly impacting photosynthetic rates. Research by Nugent-Heidel et al. (2022) on cannabis found that removing fan leaves once plants reached 50-60 cm tall in the vegetative stage improved lower bud density and cannabinoid production compared to undeleafed plants.
According to Hawke (1992), judiciously removing some larger fan leaves starting around week 3-4 of veg can boost light exposure to lower growth sites without overly stressing the plant. Sifri et al. (2022) reported maximum yields when defoliating cannabis at day 42 of veg by removing all fan leaves below the top 5 nodes, improving penetration and air circulation.
Vanhove recommends removing a maximum of 1/3 of the total leaf area at one time to avoid overstressing vegetative plants through excessive defoliation. In general, most experts advise beginning selective fan leaf removal around weeks 3-5 of vegetative growth once plants are 30-60cm tall and have established leaf canopies to benefit from improved light exposure and airflow.
We hope this quick primer helps you during your Vegetative and Flowering journey – if you have questions or comments don’t hesitate to reach out to us!
