All About Fimming Autoflowering Cannabis Plants

20 February 2023
Fimming as a plant training technique, how it is done and its benefits, difference between fimming and topping, as well as our top tips.
20 February 2023
10 min read
All About Fimming Autoflowering Cannabis Plants

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  • 1. What is fimming?
  • 1. a. What to remember
  • 2. How is it done?
  • 3. The difference between fimming and topping cannabis plants
  • 4. When to perform fimming on autos
  • 4. a. The benefits associated
  • 5. Top tips on fimming autoflowering plants
  • 6. Should you use the fimming technique on autoflowering cannabis plants
  • 7. Fimming autoflowering cannabis - faqs
  • 8. In conclusion

Applying plant training techniques to certain cultivars, can have a massive effect on the outcome of the plant appearance. Allowing a grower to manipulate the growth structure, the shape of the canopy, plant height, and final yields. In this article we explain all about fimming, how it works, the benefits associated, including our top tips.

1. What Is Fimming?

A technique that was essentially created by accident as a failed attempt at topping Cannabis plants, fimming describes the removal of 70% of the crown growth tip. The result is that the energy that would have been used to promote apical dominance is temporarily slowed down, causing a shift in growth energy to the rest of the plants.

All About Fimming Autoflowering Cannabis Plants: What is fimming cannabis

What is fimming?


Once the crown growth top has been cut away with 30% of the shoot remaining, it will take around 5-7 days before the crown shoot grows back as normal displaying apical dominance. During this time is when the remaining growth will benefit.

What To Remember

  • Fimming temporarily slows down vertical growth.
  • Energy is used for the rest of the plants as the top shoot recovers.
  • The appearance will become bushy and more stocky.
  • Removing 70-80% of the growth tip is perfect.
  • Plants will take 5-7 days before growing back as normal.

2. How Is It Done?

The art of fimming is very easy to do and should be performed using a pair of clean sterile scissors. By cutting horizontally across the cross-growth tip, and ensuring a sharp and smooth cut the technique is basically performed. If you decide to apply this technique to the main central tip, or the side branches also depends on which cultivar you are growing.

The Difference Between Fimming and Topping Cannabis Plants

Topping is performed on a plant during the vegetative stage, with the idea of totally removing the top growth top, exposing two small-sized axillary growth shoots. The plants will respond by sending all of the primary energy into these two shoots, dramatically reducing the height and width of the canopy. Topping also prevents vertical apical dominance, allowing for the side branches to be grown at the same height as the main cola.

All About Fimming Autoflowering Cannabis Plants: Fimming vs Topping

Difference between fimming and topping your plant

Fimming, on the other hand, is done with the intent of slowing down the vertical growth of Cannabis plants. The 5-7 day window as the top shoot restores itself back to normal growth allows the rest of the plant to grow causing a much more stocky and compact appearance.

3. When To Perform Fimming on Autos

It is very important that before you apply this plant training technique, you are well familiar with the cultivar and how well it reacts to plant training. Thanks to the diversity found in autoflowering Cannabis genetics indica dominant strains will prefer one style of growing, hybrids another and sativas their own also.

Fimming is used to not only bulk up plants, allowing the lower buds to become as fat as the top ones, it also allows a grower to reduce the plant height. Sativa dominant autoflowering hybrids such as Orange Sherbet Auto that can grow as tall as 150cm are well suited for L.S.T. and fimming, however, a strain such as Zkittlez Auto will finish between 70-90cm so do not need reducing in height.


Orange Sherbet Auto
5 out of 5
My wife says it doesn’t smell like weed at all when I smoke it on the porch. All she can smell is some kind of citrus fruit.
Verified customer
Reviewed 26 January 2023

The window to perform fimming should be done early on if the intention is to reduce plant height. If you are working with medium-sized plants, then applying fimming may have negative effects and cause the plants to grow very small. Once autoflowering plants have passed the 3rd week of their life cycle, it is best to avoid any type of plant training, unless you are tying down a tall-growing cultivar for the sake of the height of the grow space. 

The Benefits Associated

  • Plant will grow with a bushy and compact appearance.
  • The final height of the plant will be reduced.
  • Energy is evenly distributed to the rest of the plant.
  • Fimming is easy to perform and only requires a pair of scissors.

4. Top Tips On Fimming Autoflowering Plants

1. Make sure that you do not cut more than 80% of the top shoot off, as this can end up causing the plants to top themselves, which is the opposite desired effect.


2. Use a clean, sharp, and sterile pair of scissors when making your cut across the crown shoot. Spray the plants afterwards to keep everything clean and contaminant free.


3. Before you start fimming, do everything you can to learn about the strain and make sure that the plants will react well. Not all cultivars require fimming so do your research.


All About Fimming Autoflowering Cannabis Plants: Top Tips on Fimming Cannabis

How to perform fimming and what to avoid?

4. Never perform this technique once buds have started to form. Not only can this stress the plants, but it can also interrupt the hormone development as the plant converts itself into flowering mode.


5. For the more experienced grower, applying other plant training techniques such as L.S.T, super-cropping and pruning will all have positive effects on the overall outcome of your harvest.

5. Should You Use the Fimming Technique on Autoflowering Cannabis Plants

This is a pretty hard question to answer really. For the most part, we do not recommend using any HST (High-Stress Training) techniques at all with autoflowering cannabis strains. Why, you ask?

Well, it’s simple really. Unlike photoperiod cannabis plants, autos have an inbuilt genetic clock that automatically starts the flowering process, no matter what light timing you have them growing under. This is actually one of the huge advantages of growing autoflower seeds, but it does come with this one downside. They just do not have the time to recover from heavy strain training techniques such as topping or dimming. Any technique that involves placing the plant under such heavy stress will inevitably cause stagnation in the growth for a period of 4 to 7 days. This is fine for photoperiod plants, as we can just hold the lighting schedule at 18/6 for an extra week or so to compensate for the lost growth time. We do not have this luxury with autos, as there is no way to change the onset of the flowering period.

This does not mean you cannot use HST techniques on any auto’s, but this is definitely an advanced growing method and should be reserved for strains that you have a bunch of experience with. It is also a technique that we do not recommend for beginner cultivators unless you are ok with the possibility of killing the plant or at least severely stunting the size (and even possibly the quality) of the final product. 

But, with all that said, if you do still want to try fimming with autoflowering strains then you should give yourself the best chance of success and only try on strains that grow tall and that have longer vegetative growth periods. In general, these will be the Sativa-dominant strains that work best for HST techniques like fimming. Strains such as Orange Sherbet Auto, Gorilla Glue Auto, and the all-new and extremely popular Bruce Banner Auto are all big girls that can handle some punishment!


We have gone over (in great detail) the entire process of fimming your autos, but if you are just in the need of a quick refresher then check out our FAQ section below.

6. FIMming Autoflowering Cannabis - FAQs 

What is Fimming Autoflowering Cannabis Plants?

Fimming auto-flowering cannabis plants is a specialized gardening technique that involves cutting the crown tip itself at around the 70% mark. Unlike topping, which takes off the whole crown, fimming only takes off the tip, resulting in a denser main cola but no increase in lateral growth. Topping removes the entire crown and forces the plant to instead put its effort into the two branches that were developing just below the crown. This does force more lateral growth.


What Supplies Will I Need?

Not much really. You will of course need a sharp pair of scissors, pruning shears, or a knife. You can however use whatever type of cutting implement you feel comfortable with. Just be very careful with cleanliness and sterilization. Fully sterilize whatever cutting implement you choose to use, and wash your hands thoroughly before performing plant surgery. If you have latex gloves available, use them.


How Often Should I Fim?

This really depends on the strain, but with autos never more than once. This is due to the short vegetative growth period, and the fact that most auto-flowering strains only produce one main cola.

What are the Benefits of Fimming?

Fimming gives your plant density, which is good for both outdoor and indoor grows. The overall size of the plant will be reduced, and the growth hormones and nutrients will be more evenly distributed throughout all of the budding sites, instead of the plant focusing the majority of its energy on that main cola.


Should I Fim My First Crop?

Hell no. You want to have a bunch of practice runs before you attempt this technique. Fimming is for advanced growers, and with autos, it is best to start out by mastering the basics first. Get a few successful grows under your belt before you try any kind of plant training techniques. That way, if something does go wrong you won't have wasted your entire harvest. Even if you are the most well-versed auto grower in your area, it is still a good idea to practice with a few plants before attempting fimming on your main crop. That way you can familiarize yourself with the technique and get comfortable using it on your autos. Or, just use LST techniques like the tie-down method or ScrOG.


When Should I Fim My Autos?

Most auto growers who use the fimming technique, do so after the third or fourth node has appeared. This is a very broad statement though, and each different cultivar will need to be monitored closely and fimmed at the appropriate time.

Be sure to get familiar with the growth of your strain, so that you know when it is time to perform the procedure. This can help to ensure that your plant produces the best results possible, while also helping to make sure that it will still have enough time in its.

7. In Conclusion

On basis that you can apply the right technique at the ideal time, then you will see a big difference in the outcome of your autoflowering plants. Do not find out the hard way in which cultivars don't work well with certain training methods and do your research before getting hands-on with your ladies.