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. 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. Here’s a video showing what a plant looks like after being topped (time-lapse of about 2 weeks) FIMing. 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 Fimming 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. 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.