Pruning Cannabis for Better Structure: Topping & FIMing
Topping and FIMing are two cannabis plant training techniques that involve “pinching” or cutting off some of the top growth. These techniques are designed to give you a free way to achieve better plant shape (to make better use of the available light), create more colas, and achieve bigger yields.
Topping: Cut top of plant between nodes
FIMing: Remove newest growth (but don’t cut between nodes)
All plant training techniques are designed to help growers get a more desirable plant shape and bigger yields without changing other aspects of their grow. For example, cannabis plants don’t naturally grow in a way that takes full advantage of indoor grow lights – a lot of light is wasted indoors when cannabis plants are allowed to grow naturally without training.
Because of this, cannabis plant training techniques (like topping and fimming) are especially effective at increasing yields in indoor grow setups. Topping and FIMing are very similar in that they create a bushier plant with extra colas, but they do have some differences.
Notice how these plants have many colas instead of just one – this is due to topping and FIMing
Note: The unfortunate acronym “FIM” stands for “F*ck I Missed,” and refers to growers accidentally pinching off top growth instead of fully topping the plant between nodes. FIMing has become known as a technique of its own since it has slightly different results compared to topping (recovery time, number of colas produced in one cut, etc.).
In the above example, the plant on the left was allowed to grow naturally, which resulted in the classic “Christmas tree” shape that’s not very efficient under indoor grow lights. Some strains are naturally bushy, but these long lanky strains often produce terrible yields indoors without training. The plant on the right was topped or fimmed as a seedling. This broke the dominance of the main cola, and the plant started putting out multiple colas.
With both topping and FIMing, the growth tips that become new colas are already present. They just get bigger and become colas because topping and FIMing breaks the symmetry of the plant and exposes these growth tips to light and air. Instead of focusing on just one cola, the plant starts focusing on many growth tips until they become colas.
Topping & FIMing Involve Removing or Damaging Top Growth. This Reveals Hidden Growth Tips and Signals Plants to Start Putting Energy into Them
By damaging the main stem, topping and FIMing encourage the plant to spend energy growing many colas instead of focusing on just one.
Lower growth nodes will become new colas once they’re exposed to light and air, but they develop much faster when the main cola’s dominance is broken by topping or FIMing
Notice how these growth tips have started developing and rising up after plant is topped or FIMed (the fan leaves have been removed so you can see the new colas and overall structure more easily)
Topping vs FIMing
When it comes to FIMing vs Topping plants, it’s more a matter of growing preference than anything else. They both work great for growing marijuana!
- Cuts off top of plant at stem in between nodes
- Creates 2 main colas at the top of the plant, and LST can be used to create more
- New colas are evenly spaced (attached to the stem in the same place)
- Unlike FIMing, topping can be used to reduce the height of plant in vegetative page
- More stressful than FIMing – it takes vegetative plants longer to recover from topping
The extra main stems grow from above the node where you make the top cut. This video shows the whole cannabis topping process, in a timelapse format, showing what topping looks like in 10-14 days. The lower growth tips also begin rising up, and can produce even more main colas.
- Removes top growth, but does not cut through stem
- Creates 2-4 main colas at top of plant, and and LST can be used to create more
- New colas created are not evenly spaced
- Does not reduce height of plant
- Does not stress plant as much as topping, so plants recover more quickly or don’t even notice
These plants were FIMed early in the vegetative stage
In either case, whether you top or FIM, you will end up with a wider, bushier plant that doesn’t grow just one main cola in a Christmas tree shape.
With Topping & FIMing, you can achieve plants like this…
…In the same amount of vertical space as a plant like this
Some growers will use several phases of topping or FIMing to produce cannabis plants with dozens of colas. Some techniques take this to the extreme, for example manifolding (also sometimes called “main-lining”) is a technique that uses topping several times to make a cannabis “manifold”.
Tips for Topping & FIMing
Here are some extra tips to ensure topping and FIMing your marijuana plants goes perfectly every time!
With both topping and FIMing, you remove some of the growth on the end of a cola of a young marijuana plant, which causes the plant to stop focusing on one cola (like a Christmas tree) and instead to create many bud-laden colas (grow bushier).
If you Top or FIM the plant too early, it will have a hard time recovering. It may seem like a good idea, but you will get the best results and fastest recover if you wait until the plant has enough nodes.
Wait Until Plant Has at Least 3-5 Nodes (FIMing) or 4-6 Nodes (Topping)- Topping or Fiming a Too-Young Seedling Will Dramatically Slow Down Growth. If You Wait Until Plant is Growing New Leaves Every Day, Recovery Will Be Much Faster.
Growers use the plant’s natural response to FIMing/topping to produce short bushy plants with many colas. After the plant has been switched to the flowering stage, the wide spread of colas allows the plant to efficiently use indoor grow lights to produce the biggest yields possible.
If you choose to use either of these methods, you will get the best results by doing it when the plant is young, usually when it has around 3-6 total nodes formed. Generally, you would only want to FIM a plant that has just 3 nodes, and wait until 4 nodes to top the plant.
These young cannabis plants are almost ready to be topped or FIMed. Cannabis plants can be FIMed before they can be topped.
You get great results by breaking the tendency of the plant to grow one main cola while the plant is still short, because you can arrange your multiple colas however you want as the plant develops, instead of dealing with a Christmas tree shaped plant.
You can also top or FIM your plant later in the vegetative stage, but you will have a longer main stalk, giving you less ability to arrange the colas the way you want.
After being topped or FIMed, your plant will need some time spent recovering in the vegetative stage, though generally this just causes the plant to ‘fill out’ more instead of growing taller, which is often desirable for indoor growers.
This plant was trained for ~2 dozen colas in the vegetative stage
Important: Don’t Top or FIM in the Flowering Stage; It’s Too Late!
Topping and FIMing techniques should only be used in the vegetative stage! In fact, any training technique that involves cutting or damaging your plant should optimally be done in the vegetative stage of cannabis growth, before the flowering/budding stage begins.
In the flowering stage, only gentle training techniques such as LST or other types of bending should ever be used to change the shape of the plant.
A plant with many colas can only be achieved by training a plant from early in the vegetative stage
Cannabis plants are much less tough in the flowering stage, and they no longer grow vegetatively (producing new stems or colas) by the time they hit about week 6.
If you watch a plant in the flowering stage, you’ll see that it doesn’t get taller or develop growth nodes after about week 6. It only “focuses” on making buds. Topping or FIMing at this point won’t do any good. Damaging your plant during the budding stage will often cause a reduction in your final yields because you’re just taking away more plant/bud sites and may cause unnecessary stress during the crucial bud-building phase.
By the time your plants are in the flowering stage, much of the growth structure has already been created, and you generally need to try to manage as best you can if your plant has grown into a shape you don’t like.
What if my plant is already too tall in the flowering stage?
If your plant is already too tall in the flowering stage for your grow setup, you’ve got to take immediate action to prevent the plant from getting any taller.
My suggestion is to use bending (LST) your plant to control the height of further growth. Very careful super cropping can also be used if you have a far taller stem than the others.
Once flowering is fully underway (after the initial flowering stretch), the plant will not grow much taller, so you can just try to hang on until harvest. Sometimes you may even have to harvest a particularly tall cola ahead of time to prevent it from getting bleached or burned. Don’t stress, it happens to us all! I recommend trying to take it as a learning experience
How Can You Tell That Your Plant is Diverting Energy to New Colas?
Almost immediately after topping or FIMing, the connections to each node become enlarged at the base.
These thickened connections demonstrate that your cannabis plant spreads energy evenly across the whole plant.
When you see your plant thicken connections like this, it means that the plant is strengthening the “internal system” of the stem, so it’s easier to deliver nutrients and other building blocks. This results in faster growth, bigger colas, and increased yields for each affected stem.
The thickening that happens at the base of stems is one sign that the plant is diverting energy to the new colas (where before it was putting the majority of its energy into just the one main cola).
As time goes on, the most used stems can become so thick they’re almost like tree trunks.
Topping Your Cannabis Plant
When topping your cannabis, you cut off a growing node of the plant, reducing the height instantly. This can be especially beneficial if you’ve let your plant get too tall. Topping also increases the number of colas, which can give you more bud at harvest,
When topping your marijuana plant, it’s best to top the plant when it is young, and has 4-6 nodes (sets of leaves) in total. Although you could do it a little earlier, you’re more likely to accidentally stunt your plant the younger it is. Additionally, the less actual plant matter you take off, the less likely the plant will get stressed. Think about it, if you’re taking off 10% of the plant it will have much less effect than if you took off 30% of the plant.
“Topping” the plant means cutting off the newest node on your marijuana plant’s main cola in order to split it into two. However, the word “topping” can also refer to cutting of the tip of any stem.
A good place to top is directly above the leaves of the next node. In other words, cut through the stem right above its next set of leaves from the top.
Topping will cause your plant to transfer its energy to two new main colas, as indicated by the two yellow dots in the diagram above.
Make sure to leave a little extra stem behind for reinforcement. This helps strengthen the two new colas to prevent them from splitting down the middle.
These 2 new colas for a V which can easily be bent to spread wide. You can top these two new colas a few weeks later and have 4 total colas. This can even be doubled to produce 8 colas that all come from a single “manifold.”
Another benefit of topping is how the plant tends to grow bushier afterwards, spreading its energy much more evenly around to the whole plant.
Often lower branches rise up to become new main colas. This is especially true if you combine Topping with LST to open up the plant so the lower branches get more light.
If you’ve grown a very tall plant, it’s also possible to top your (vegetative) plant down to the node you want to reduce the height, but remember that all the time the plant spent getting tall will be lost. To get the most flexible colas, without losing vegetative time, try to top or FIM early in the plant’s life
If you’re still in the vegetative (non-budding) stage and plants are growing way too tall, you can top the plant immediately to remove height as needed. The time spent growing the extra growth will be lost, so this may add time to the veg stage.
If you want to top the plant multiple times, you may be interested in learning about main-lining (creating a manifold – a plant training technique).
FIMing Your Cannabis Plant
FIMing is generally less traumatic to the plant than topping. FIMing barely slows down growth and can stimulate the plant to grow up to 4 main nodes in one cut (instead of just 2 like with topping).
FIMing will often not make symmetrical colas like topping. The resulting number of colas becomes less predictable.
With FIMing, the 4 new colas created are not evenly spaced, and do not join to the stem in the exact same place. This might not matter to some growers, but is useful to know when using a technique like main-lining where it’s important for nodes to join at the same place on the stem.
Never FIM Cannabis in the Flowering Stage!
More About FIMing (Pinching) Your Marijuana Plant
Note: FIM (unfortunately) stands for “F*ck I Missed” referring to the fact that it’s like topping your plant, only you’re taking off about 20% less.
With Fimming, you can get less consistent results than with topping. If you don’t actually pinch off the top growth just right, you may end up with only 2 or 3 colas instead of 4.
The 4 colas also may not grow as evenly as the 2 tops that are achieved with topping. If you top your plant twice, you will end up with 4 colas just like FIMing, but you will generally get more consistent results. However, topping the plant slows down growth more than FIMing, so it’s up to you to decide what’s best for your situation.
All you need to do is remove the top growth
Instead of cutting the plant, which can sometimes accidentally result in topping, many growers instead choose to crush the top of the plant between the fingers, without removing any part of the leaves. However, I recomment removing plant matter and only leaving about 20% behind. This gives more consistent results.
It’s best to FIM a plant with 3-5 nodes. While you can FIM a taller plant, there will still be a long main stem and your new colas won’t be as flexible as colas from an early FIMed cannabis plant.
FIMing an older plant will leave you with one long main stem, but lower growth tips start growing up
FIMing is sometimes referred to as “pinching off” the top of the plant. To FIM the plant, you simply pinch or cut off the newest growth, taking just the tips of the newest growth off, and making sure to leave a bit behind.
FIMing causes the plant to grow very bushy, and the other nodes will becomes strengthened just like when topping.
FIMing barely slows down growth since very little of the plant is removed.
Be warned, when FIMing your plant, the top growth on the plant will look weird when growing in. This is normal!
Topping and FIMing are both great choices, and the best technique depends on what you’re trying to achieve!