There’s no shortage of cannabis training methods out there that offer one advantage or another to intrepid growers. Fimming is one of the newer, and lesser-known, methods that aims to promote lateral branch growth for a shorter, bushier plant. If you’ve ever tried topping, then fimming is worth your consideration.
What is fimming?
Fimming (or FIM) is an advanced growing technique that aims to create bushier cannabis plants that are more focused on lateral (as opposed to vertical) growth. In short, the practice is very similar to topping a plant with the only major difference being exactly where you make the cut.
The story behind fimming goes something like this.
An ambitious but hasty grower was attempting to top their plants but they made the cut in the wrong place and, in their frustration, shouted “F*ck, I missed!” (FIM). However, after a few days, their plant was growing healthy new branches from the spot where they cut resulting in a truly impressive harvest.
This single mistake gave way to an entirely new method of controlling a cannabis plant’s shape and size and today fimming is an increasingly popular technique among growers who are looking to shake things up a little bit.
Fimming vs topping
Fimming and topping are incredibly similar. If you’ve ever topped a cannabis plant, then you can fim one with little trouble. For the uninitiated, topping (sometimes called “apical pruning”) a plant is the practice of snipping the uppermost growth of a vegetating plant. This results in the stem splitting into two main stalks, each of which will grow into its own cola. This can effectively double your harvest compared to an untopped cannabis plant.
Fimming is performed effectively the same way with the only major difference being exactly where you make the cut. While topping requires the removal of the entire uppermost growth node, fimming only calls for the removal of 70-80% of the node. It might not sound like much of a difference, but the results are noticeable.
When topping a weed plant, the remaining stem splits into two new stalks and the plant will send the bulk of its resources to these. This results in a plant with two main stalks that will be the focus of flower production with each growing a full cola. Most topping is done early in a plant’s life and lower branches are largely ignored (or even removed) to focus on the colas.
Fimming, on the other hand, merely slows the plant’s vertical growth for 5-7 days, forcing the plant to divert its energy to the remaining healthy branches. This results in a bushier plant with more flowering sites spread across larger, sturdier branches.
Fimming vs pruning
Broadly speaking, fimming is a type of pruning. Pruning is simply the act of removing part of a plant for optimal growth. This could be as little as trimming away a few leaves or as extreme as mainlining. Since “pruning” is such a broad term, it’s rarely used on its own.
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What are the benefits of fimming cannabis plants?
Much like any other high-stress training (HST) method, the main goal of fimming is to force your cannabis plant to grow more flowering sites to increase its overall yield. While fimming is regarded as something of an advanced technique, anyone with a pair of good sharp scissors can pull it off with minimal risk.
Compared to topping, fimming is less stressful on the plant meaning that it should recover more quickly. There’s also a bit more room for error, meaning that you don’t need to be as precise. The whole idea was born from a mistake, after all.
Properly fimmed cannabis plants are shorter and bushier than untended ones and it’s possible to easily avoid the standard Christmas tree shape that most plants default to. This is desirable because a large and even canopy is the best way to maximise your final yield.
Unlike topping, fimming distributes the plant’s energy to the remaining branches as opposed to just the newly-topped stalks. This results in more overall flowering sites spread out across a wider canopy.
One of the biggest advantages of fimming, however, is its versatility. Topping can only be performed on the top of a plant (shocking, I know). Comparatively, fimming can be done to any part of the cannabis plant that is experiencing new growth. Fimming lower branches can help to eliminate the formation of “popcorn buds” and make those “useless” sites incredibly productive.
If you’re ScrOG growing, fimming is an incredibly useful technique thanks to its versatility and rapid recovery time. When combined with other LST techniques, plants grown this way can be trained to fit just about any shape or size.
Potential risks of fimming
There’s no perfect system and fimming isn’t without its risks. The biggest risk of fimming your weed is accidentally cutting off too much of the growth site. But even this isn’t a huge problem as all that you’ve done is effectively top the plant. While that might not have been what you were trying to do, the results won’t damage your plant in the long run.
There is a risk that the new branches that grow may be too weak to support new growth and flowers. This usually occurs when not enough of the original growth is removed. It’s a very fine line to walk here and practice is the only thing that will help you consistently find the sweet spot.
The downsides associated with fimming are the same as those associated with topping:
- Longer vegetating times and a significant amount of stress on the cannabis plant.
- The use of non-sterile tools can introduce contaminants to a plant that can potentially cause serious damage.
- Fimming too early can kill a plant and fimming too late can reduce your overall harvest. The ideal time will vary from strain to strain, but the 2-3 week mark is typically a safe bet.
Compared to topping, fimming typically results in taller plants (thanks to the shorter recovery time) and the colas that grow are a bit less evenly spaced than a plant that has been properly mainlined. These aren’t major issues, but if you plan on fimming your plants, you’ll want to make heavy use of LST training as well.
Lastly, it’s worth mentioning that not every strain is ideal for HST. Some strains are incredibly prone to stress and are best left untopped. Do some research into what strains best fit what techniques you want to use. Stains like Amnesia, Lemon Haze, or Strawberry Kush are all good candidates for fimming.
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How to fim cannabis plants
Now that we know all about what fimming is and why you might want to do it, let’s get down to business. If you’ve ever topped a plant, then fimming will be a breeze. If this is your first time trying something like this, don’t worry, it’s really quite simple.
- Sterilise your equipment. Using rubbing alcohol, make sure that your scissors (or razor) are as clean as they are sharp. Dirty blades can cause infections and introducing anything to an already stressed cannabis plant is a recipe for disaster.
- Select your target. Typically, this will be the highest point of growth on your cannabis plant, though the tips of lateral branches can also be fimmed.
- Make the cut. Grip the leaves between your thumb and forefinger and pull them very gently so that they are taught. Then, make a single horizontal cut that removes 70-80% of the growth.
- Wait. After 5-7 days, you should see new growth forming as the area you cut has now split into two new branches.
- Repeat as needed. Fimming doesn’t have to be “one and done”. If you’ve got time and you want to push your plant to the limit, then you can do it over and over again. However, it’s worth noting that plants can be over-fimmed resulting in more branches than the roots can support. This will lead to a weaker cannabis plant with smaller yields. There’s no single rule for learning when enough is enough, but in my experience less is more.
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When to start fimming plants
As with any other HST technique, it’s important to wait until the cannabis plant is healthy enough to survive the process. Typically, it’s a good idea to wait until the plant has 5 or 6 nodes before attempting to fim. At this point, the plant is still in the vegetative stage, but is developed enough to handle the stress.
With that said, earlier is generally better than later as the point is to direct the size and shape of the plant. It’s also important to start fimming well before you plan on flowering. Fimming during flowering is a huge no-no as it will completely ruin the yield of your plant. This is generally true with any HST technique but it bears repeating. Do notfim your plants within two weeks of making the switch to flowering! They need time to recover before they can properly enter the flowering stage.
Can I fim autoflowering plants?
Generally, I would advise against using HST techniques on any autoflowering plant. They grow too quickly and any amount of stress is likely to cause permanent damage if not done perfectly. However, it is technically possible to fim an autoflowering strain, especially if you have gained some experience with fimming already. There are several things to keep in mind if this is your plan.
First of all, you’d need to use a sativa-dominant strain as these have longer vegetation times. Many indica-dominant strains have vegetating times as little as 3-4 weeks meaning that you only have a window of maybe 3 days to actually do the trimming. Too soon and you can kill your plant, too late and you can ruin your yield.
It’s also worth mentioning that if you plan on fimming an autoflower plant, it’s best to err on the side of caution when deciding how much growth to remove. Cutting off too much can completely halt the growth of your plant just as it’s entering the vital pre-flowering stretch, meaning that the size of your plant will be seriously reduced.
If you’re looking for good strains for fimming, consider something with known for robust growth and rapid development. Strains like NYC Diesel, White Widow, or Northern Lights are all great choices for fimming or any other HST techniques.
Take a chance
Fimming is just one tool in a grower’s arsenal and won’t be a perfect fit for everyone. However, it’s certainly a technique that’s worth trying out at least once if you’re curious about just how far you can push your weed plant. Thanks to the ease and speed with which fimming can be done, it’s a valid choice for many growers.
