Fimming, FIMing, or “F***, I Missed” is a high-stress plant training technique that is commonly employed by weed growers. It is used to increase the number of flowering sites a plant produces, as well as promote a more lateral growth pattern.
Why would you want to force your crop to grow in a horizontal direction?
For a few reasons, actually. We all know the classic ‘Christmas tree’ shape that untrained weed plants take. They grow tall, with a main stem and one dominant cola (or bud) at the very top. This shape is great for outdoor grows where you want to maximize light exposure and has proved to be evolutionarily advantageous, giving us the strong, durable, versatile plants we know and certainly love.
But, when growing indoors (and sometimes outdoors, depending on the strain, climate, and your cultivation goals), this shape may not be ideal. Some growers want their plants to grow more horizontally, in order to maximize space and yield potential by having more flowering sites.
Other growers use Fimming to promote a more even canopy, leading to greater light penetration, better air exchange throughout the plant, healthier plants, and potentially higher yields. Much bigger yields.
No one knows for sure where fimming first originated exactly, but it rose to prominence in the North American growing community in the early 90s. Topping, another high-stress plant training technique that leads to very similar outcomes to fimming, has been around for a lot longer.
The big difference between the two is the amount of plant material that is removed, and the growth pattern that results from this difference. While topping involves cutting off the main growth tip completely, which forces the two branches just below the cut to grow horizontally and take over as the main growth tips, Fimming involves cutting off the top of the main growth tip partially. This leaves behind more plant tissue and results in multiple branches (between 2 and 8) growing from the same growth tip.
Yep, it sure does. The story goes that a grower was trying to top his plants by cutting off the main growth tip and accidentally missed. Instead, they cut off just a portion of the top, leaving behind some leaves and plant tissue.
Most growers would probably start panicking at this point, thinking they had just ruined their plant. Not this dude (or lady, who knows). They left the plant be to see what would come of it, and were pleasantly surprised to see multiple branches growing from the cut site. This happy little accident started the trend of partial topping or Fimming. And the name stuck.
We have mentioned that Fimming is pretty similar to Topping, but what are the exact differences?
Well, when you top a plant, it is forced to grow horizontally in two main branches. But with Fimming, instead of just two branches growing at the cut site, multiple new branches will grow from the same spot. This results in a much bushier, fuller plant that can produce more flowering sites and potentially lead to higher yields.
When you remove the growth tip of a cannabis plant, whether through topping or fimming, you break the apical dominance of the plant. This means that the plant can no longer rely on one main growth tip to determine its shape and direction of growth. Instead, multiple new growth tips will compete for dominance, leading to a bushier and more even canopy.
Ok, but why does fimming result in so many more branches than topping?
It all comes down to internodal spacing, especially in that growth tip that you are going to cut. The nodes are where each new set of leaves and branches grow from, and the space between each node is called the internode. In the growth tip, there are a bunch of nodes all squashed together. When you top a plant, you remove those nodes, but with Fimming, some of them remain. These remaining nodes are just waiting for the apical dominance to be broken so they can start growing and becoming new branches.
Just like with any form of plant training, and especially with high-stress techniques, there are certain benefits and drawbacks. Let’s look at some of the pros and cons of Fimming.
Before we get into the actual process of fimming, let’s go through the equipment and materials you will need:
When it comes to scissors, the phrase ‘sharp as a razor’ is no exaggeration. You want to make sure your scissors are clean and sharp in order to minimize the damage done to the plant and increase the chances of success. And not all pairs of scissors are created equally, at least not for this task.
If you have already grown a few plants, then there’s a good chance that you have already gone out and bought a pair of dedicated cannabis trimming/manicuring scissors. These are the best options for fimming as they are extremely sharp and precise, making it easier to make a clean and precise cut. But, for the best possible outcome with fimming, you’ll want to use a set of curved weed-trimming scissors. These were originally designed for bonsai trimming, and they’ll give you more control over your chopping. But, the real deal pairs do come at a price. Not to worry, though, there are a bunch of cheaper options available.
There are two main styles available:
Whichever you choose, you’ll end up using for years, so the price is really a one time investment. Anyway, let’s not get too carried away with the trimming scissors – just make sure you have some sharp, clean scissors, and if you can find a curved pair, then all the better.
Why are curved scissors better for fimming?
Well, as the plant grows, it forms a V-shape where the new growth tips emerge. If you use straight scissors to cut off this tip, there is a chance that you will accidentally snip off some of the plant material that will eventually turn into the new branches. Using a curved blade just makes it easier to get in close and make a clean cut without damaging any potential new branches.
You should wait until the plant has grown at least 3 – 5 nodes before considering making your first cut. This will give the plant enough time to bulk up that lower part of the main stem.
Outdoor growers who are utilizing the entire growing season might attempt fimming up to 3 times, ideally waiting at least 2 weeks between each cut. However, indoor growers usually don’t let their plants stay in the vegetative stage long enough to make multiple cuts. They usually fim once, then switch to the flowering stage once they are happy with the plant’s size and structure.
As just mentioned, fimming will extend the amount of time weed plants need to spend in the 18/6 vegetative growth stage. You should be expecting to keep your plants under the vegetative light schedule for at least 5 or so weeks if you plan of either fimming or topping.
Fimming, especially when done correctly and resulting in 5 or more new growth points, will also make the plant a little unbalanced. All of a sudden there are going to be a bunch of branches reaching out sideways, and these branches are eventually going to fill up with flowers. Not a huge issue, as this can be counterbalanced or supported through the use of other training techniques, (even for autoflower training techniques) which we will dive into a little further down.
There’s no one straight answer to this question, because it largely depends on how much of the top was fimmed, how well the cut was made, how healthy the plant was before being filmed, and the cleanliness of the tools used. But one thing is certain – there will be a delay in the growth. Whether it is just a day or two, or more than a week is really down to your skill, the size and health of your plant, and a bit of luck.
The more you fim in one go – i.e. the more aggressive you are with your fimming – the longer it will take to recover. This is because fimming more causes a greater alteration in the way your plant grows and distributes resources for regrowth. Spreading out multiple fimming over a few weeks is far less stressful and can be likened to giving your plant a regular haircut, as opposed to shaving its head.
Another factor in recovery time is the health of your plant before fimming. Plants that are already in great shape will recover much quicker than plants that have been struggling with dryness, pest infestations, nutrient deficiencies, or any other kind of stress. This is because they have the resources to put into regrowth already in their leaves and stems, whereas plants that are struggling may need to first use those resources for repairing existing damage.
And even if everything went perfectly and you only fimmed a small portion of the tip, your plant will still take some time to recover. Just think – you’ve cut off the very top growth point (or more) that it was dedicating its resources to, and now it needs to readjust and focus on a different growth point or points. This takes time, which is why fimmed plants experience stunted growth for a while after fimming.
Can you just fim your crop and then leave it grow?
Of course you can, but you fimmed for a reason, right? You want that plant of yours to reach its full yield potential, yeah?
Well, to do so, you are probably going to have to use some more techniques, such as pruning, SCroGging, and supercropping. In fact, when these three techniques are combined with fimming, you are looking at a perfect storm for the creation of a highly productive marijuana plant.
Pruning is where we remove certain parts of the plant to help shape it, promote more growth in certain areas, and increase canopy space for more light penetration and airflow to reduce the risk of mold or mildew. It also helps redirect resources to the plant’s main colas (the large, central buds) rather than smaller side branches that won’t produce as much.
No matter if you are fimming or not, you should be constantly checking on the plant and looking for any dead or dying leaves, damaged branches, or overcrowded areas that may be causing issues. Pruning these away will help your plant focus on healthy growth and prevent any potential problems.
The lowest sets of branches can be taken straight off the plant, as they only produce airy, wispy, popcorn buds. You can also remove any larger fan leaves that are blocking light from reaching budding sites below, but do so in moderation. No more than 25% of the fan leaves should be removed at once, as they are still important for photosynthesis and overall plant health.
Screen of Green (SCroG) is a technique that involves using a screen or net to support the plant’s growth and allow for better light penetration to the budding sites and airflow through the canopy. This is the perfect accomplice to fimming, as it helps regulate the plant’s shape and allows for a more even distribution of light.
To implement SCroGGing, you will need a sturdy screen or net that is able to support the weight of your plant’s branches and buds. when you have about a week or so of vegetative growth left, place the screen horizontally, about half a foot or so above the plant. As the plant grows, weave and tuck branches through the holes in the screen so that they are more evenly distributed, and tie them loosely in place.
When implemented correctly, every single one of the flowering sites of the entire plant can be manipulated to receive the same amount of light, and thus grow in a more even way. This allows for a larger harvest compared to just letting your plant have free rein on which branches get access to the most light.
Supercropping is another high-stress training techniques designed to alter the way your plant grows in order to maximize yield. Instead of topping or fimming, supercropping involves strategically crushing and bending certain branches at their soft points in order to create an open canopy that allows for better light penetration.
Now, when we say crushing and bending, we mean doing so extremely carefully. By pinching the branches until you feel the internal structure “pop” while leaving the outer layers of the branch intact, you can bend and shape while also forcing it to send resources to the newly shaped branches. This can also increase nutrient and water uptake, as the plant will think it needs to repair the damage done.
Supercropping can cause a bit more stress than fimming or even topping, so make sure not to do too much at once and always keep an eye on your plant’s recovery. But when done correctly, it can greatly enhance yield potential and promote strong, healthy growth.
Both topping and fimming have their own unique benefits, but ultimately it depends on personal preference and the individual plant’s needs. Topping removes the entire top portion of the plant, creating two main colas that will grow upwards. This can be beneficial for plants that tend to stretch too much or have weak branches.
While fimming only removes a small portion of the top, it allows for more control and direction of growth as well as the potential for multiple main colas, but comes at a cost. It is more stressful for the plant and may require more recovery time, so it’s important to assess your plant’s individual needs and monitor its progress closely. It also comes with a higher failure rate, especially for novice cultivators.
Does this mean you should just stick to topping?
Nope, not in our estimation anyway. Growing weed should be fun, and what’s more fun than experimenting and trying different techniques? You might as well try both topping and fimming on different plants to see which works better for you. Keep in mind that every plant is different and may respond differently to each technique, so it’s critical to observe and adapt accordingly.
In the end, both topping and fimming can greatly enhance your plant’s growth and yield potential, especially when combined with other techniques like pruning, SCroGging, and supercropping. So go ahead and give them a try, and see which one works best for you and your grow. Don’t be afraid to experiment and find the perfect combination of techniques that works for you to achieve maximum yield from your pride and joy, that weed garden that you can’t keep outta your head.
Sam North is a content writer with a passion for everything cannabis. After working multiple seasons on weed farms absorbing the ins and outs of cannabis cultivation and culture, he decided to transition into a role that would allow him to work from anywhere, anytime. Sam now writes for multiple weed publications. He has extensive experience with a wide range of canna-agriculture styles, from smaller artisanal farms to large-scale commercial operations, and is here to share his knowledge to give you all the best chance of cultivation success. About this Author