Topping VS Fimming - Which Is Best For Autoflower?

Get more compact growth structure, reduced height and bigger buds using these techniques.
29 April 2020
4 min read
Topping VS Fimming - Which Is Best For Autoflower?

  • 1. What is the difference?
  • 2. How does topping work with autos?
  • 2. a. Benefits of topping
  • 3. How does fimming work with autos?
  • 3. a. Benefits of topping
  • 4. In conclusion

When it comes to these two plant training techniques, the actual difference between the two is very small. Understanding the purpose of topping and fimming autoflowering can have many benefits associated, from a more compact growth structure, reduced height, and bigger buds. In this article we compare topping and fimming, explaining the advantages of each, when to apply and what to consider.

1. What Is The Difference?

Fimming was created by accident and the word FIM is an abbreviation for "Flip I Missed!”, in reference to a failed attempt at topping the plant cleanly. Doing this accidental technique and purposely leaving 25% of the top shoot remaining, growers noticed that their Cannabis plants would respond by growing with a much more stocky growth structure as well as with limited vertical growth. There will be a time frame of around one week where the plants recover and begin to grow back to normal focusing on vertical growth.

Topping, on the other hand, is when the main crown shoot of a Cannabis is cleanly removed. What is left behind will be known as axillary shoots. In response to the loss of the main crown shoot, the plant will encourage the two shoots to grow, allowing the plants to develop two main central colas instead of one. Plants will respond instantly and the distribution of growth hormone auxin is reduced.

2. How Does Topping Work With Autos?

When we are working with autoflowering Cannabis plants, there is a window of 3-4 weeks in which all types of plant training should be performed. As described above, topping will disrupt the growth hormone responsible for the vertical growth and main cola, which may or may not be advantageous to specific cultivars.


Topping VS Fimming - Which Is Best For Autoflower?: How Does Topping Work With Autos?

Topping means the removal of the main crown shoot, resulting in two auxiliary shoots at the highest point of the plant.

The main benefit of topping autos is to help control the final plant height of a sativa dominant hybrid, producing a more uniform and lateral dominant canopy. We advise only topping autoflowering strains that have a tendency to grow quickly and finish as tall as 150cm, like Orange Sherbet Auto.

Orange Sherbet Auto
5 out of 5
I grew this with other fast buds strains. I'm very happy how they all grew. I use soil, 19L pots on a 20/4 light cycle. They love it.
Verified customer
Reviewed 23 October 2020

The way to perform topping is to allow the plants to grow tall enough so you can easily remove the crown shoot from the top internode, then cleanly remove with a pair of clean and sterile scissors.

Benefits Of Topping

•  Outdoor growers will find topping useful at dramatically reducing the final height of the plant. Some cultivars that can grow as tall as 150 cm, will benefit the most allowing for a more discreetly grown crop on a terrace, balcony, greenhouse, or back garden.

•  The growth structure of the plants will change from vertically dominant, to a more bushy Christmas tree appearance. Side branches will benefit and be given a chance to grow alongside the main crown shoots, causing a much more even and consistently producing top canopy.  

•  When working with a SCROG set up, topping autos can be very advantageous. Be sure to check the cultivar you are growing is well suited for a Screen of Green that uses a net for the canopy to be grown through. 

•  Topping Cannabis only needs to be performed once for the desired effect to be achieved. This should be done once the plants have grown past the 2nd or 3rd internode.

3. How Does Fimming Work With Autos?

Applying fimming at the right time will allow you to reduce the vertical growth, and at the same time encourage energy transfer to the lowest-growth sites. The result is the foliage and stem size will grow much quicker and by the time the crown shoot has recovered, the rest of the plant has caught up with the upper part.

The advantages are all of the buds from top to bottom with finish with an almost identical size and structure, eliminating the concern over undeveloped, lower popcorn buds.


Topping VS Fimming - Which Is Best For Autoflower?: How Does Fimming Work With Autos?

Fimming describes the removal of 70% of the crown growth tip, causing a shift in growth energy to the rest of the plants.

It is very important that fimming is only applied prior to plants producing flowers and should really be done with cultivars that can afford the reduction in height. Be Careful if applying fimming to short and stocky indica dominant cultivars as this can cause plant height to stay very low unless that is the goal. 

Benefits Of Topping

•  Apical dominance is temporarily stopped, and growth energy evenly distributed to the rest of the plant pathways. Unlike topping, vertical growth will resume back to normal after 5-7 days, giving you some control of the plant's final height and overall appearance.

•  Fimming is easy to perform and can really enhance the growth structure of an autoflowering Cannabis plant. Make sure that you use a clean and sharp pair of scissors and be extra careful not to remove more than 75% of the crown shoot.

•  Lower buds will have the opportunity to grow at the same rate and size to the higher parts of the plant. When using L.S.T. and carefully fimming, the end results can be spectacular resulting in a very large-sized plant with consistent bud development throughout. 

•  A great way to reduce the final height and still grow stocky and dense plants. It is best to use more sativa dominant hybrids as short indicas may not react as well.

4. In Conclusion

Both of these easy to perform techniques have their own pros and cons. We recommend researching which autoflowering strains are best for plant training, as stated by the seed banks. Finding the right amount of plant training can be a balancing act that takes time based on your experience, growing space, and cultivar. 

29 April 2020