• Post last modified:May 4, 2022
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Topping cannabis is one of the popular training methods cultivators utilize to control height and maximize yields. The method is easy to execute and thus isn’t restricted to experienced cultivators. Once a grower identifies how to top cannabis plants, when to do it, and what to do after, they are on their way to attaining an impressive harvest. 

Fimming is another similar training method that promises similar results. The technique may need some practice to execute flawlessly, but the results are worthwhile. This piece is a guide to everything you need to know about topping cannabis, including how to do it. It also explores fimming and its similarities and differences with topping. 

What is topping?

Topping is a technique that involves cutting off the main shoot of a cannabis plant. Traditionally, cannabis plants take on a pine or Christmas tree shape. This is especially true for Sativa plants, which tend to extend vertically. With topping, a cultivator alters the growth pattern and direction of the plants; instead of focusing on vertical growth, the plants stretch laterally, allowing light penetration to the lower plant branches. 

How does this happen?

The pine shape results from a phenomenon referred to as apical dominance. This happens when the main shoot produces Auxins, hormones that suppress the growth of the branches below. As a result, the top part of the plant ends up getting maximum light exposure at the expense of the lower branches. The growth-inhibiting hormones do not travel for a long distance, so the length they can cover in the phloem is limited to the few branches below the main cola. 

Consequently, as the plant grows, the branches furthest from the apex break free from the dominance and begin to stretch, thus creating a triangle shape. The flowers produced by such a plant include one gigantic, healthy cola and substandard ones below it. 

When the central cola is removed, the shoots located on the branches under where the cut is made become the main shoots. They will grow exponentially over the next few weeks, which would have never happened if the main cola had been present. Topping can be done one to six times during a plant’s vegetative phase to maximize size (more on this later on).

Once the apical dominance is eliminated by removing the central shoot, the rest of the plants get a fair share of light distribution, leading to optimum lateral growth. Topping inverts the plant’s shape from a pyramid to a cocktail glass. The extension of branches creates more space for bud formation, resulting in higher yields

Top reasons and benefits attached to cannabis topping

Topping can be done in outdoor or indoor-grown plants for various reasons and benefits, including;

  1. To facilitate better yields
  2. To limit vertical height, especially when working with a grow space with limited space
  3. To keep the plants away from prying eyes by limiting their height, making them less conspicuous.
  4. To shorten the growth period by instigating accelerated growth
  5. Make the cannabis plant easier to work with as it can be difficult to grow a 4-meter plant and care for it appropriately
  6. To keep the plant in constant growth to produce clones as a mother plant.

Topped plant vs non topped plant

There are considerable yield and plant size differences between a topped and a non-topped plant as highlighted below;

Topped cannabis plantNon topped cannabis plant
Wide plant that allows light penetration to all parts of the plantTriangle-shaped plant with light exposure concentrated on the upper leaves on the central cola
Numerous, healthy colasOne central, healthy cola at the top and several, small and undeveloped colas at the bottom
Double to quadruple the normal plant yieldNormal yield
Controlled height makes growing in spaces with limited vertical space easierCan only be grown in large spaces

Cannabis plant that has just been topped

topping cannabis

This is a cannabis plant shortly after topping. After some more growth you can use the LST method to tie down any additional branches to force them to grow wider, this will allow each branch to receive more light and develop plenty of bud.

Topped cannabis plant

topped plant vs non topped plant

As you can see from the fully grown plant a cannabis plant that has been topped produces multiple bud sites instead of the typical one main central stalk if left to grow naturally. The result is lots of large colas and a very healthy yield.

Non-topped cannabis plant

non-topped cannabis plant

As you can see without proper training a cannabis plant will grow into a Christmas tree style shape. With this particular plant all that has been used is some bamboo supports to assist it as it grows taller. You can see however that the side branches are much less developed than the main stalk, their leaves will also receive less light due to their positioning and hence they will yield much less than if they had been topped and trained using LST.

When and how to top cannabis

While topping the plants is an easy-to-execute procedure, identifying the right time to do so presents a challenge. Topping the plants too early may lead to stunted growth and compromised bud quality. Topping too late wastes time that the plant would have utilized to grow laterally. According to expert cultivators, the right time to top cannabis plants is 30 days after germination (4th to 5th week). During this time, the plant will be in the vegetative stage and have developed five or more modes. Additionally, the lower nodes will have already started experiencing secondary growth. 

Being in the vegetative stage is not enough. You need to top the plant when it is at its healthiest state. Topping is a high-stress procedure that will put the plant in shock for a day or more. It needs to be capable of bouncing back from the trauma and grow exponentially for optimum yield. Before topping, consider the following factors;

Soil health

Ensure the soil is adequately packed with nutrients to support the change from vertical to rapid lateral growth. The plant will need extra nitrogen than usual to support the recovery process. Nitrogen is an essential element in photosynthesis and acts as a building block for proteins. 

The PH value is also an important factor to consider before topping cannabis plants. Are the PH readings within the normal range (6 to 7)? Anything outside this may greatly affect the plant’s growth. The goal is to have all the growth factors in check before topping the plant.

Light 

Is the plant receiving sufficient light exposure? A plant should be subjected to the 18/6 (preferred) or 16/8 light schedule during the vegetative stage. This ensures it gets enough light to create sufficient energy to maintain overall health while still getting enough time to rest.  

Pathogens, diseases, and deficiencies

Is the plant healthy? It will be futile trying to top a plant battling powdery mildew, heat stress, pests, or deficiencies. Doing so may lead to crop loss due to its inability to recover. 

Water

What is your watering schedule? Are the plants getting sufficient water to transport nutrients and remain hydrated? Maintain a steady watering schedule, but be careful not over-water the plant as it causes nutrient dilution, dropping leaves, and slow growth.

Where to cut 

Topping targets the area above the fifth node. Some cultivators top above the fourth node, while others do it on the sixth. Where to cut largely depends on the plant’s ability to recover from the procedure. A node refers to the junction where side branches grow from on the main stem. The stem between two nodes is an internode, while the space between two nodes is called internodal distance. 

How many nodes before topping?

When topping cannabis you want to make sure the plant is well established enough to handle being topped, after all, the aim of topping is to damage the plant to encourage further growth. If this is done while the plant is too young it may not recover as well so ideally you should top a cannabis plant once it has produced 4 or 5 nodes.

If you are reading this and your plant is already at a later stage of growth with maybe 5 – 8 nodes don’t worry, you can still top the plant at this point, however the results probably won’t be quite as good.

The process of topping a cannabis plant

Now that you know where to cut, it is time to make the cut. You will need pruners, scissors, or a razor blade and rubbing alcohol. Ensure the cutting apparatus is sharp enough to make a precise, clean cut. Use the rubbing alcohol to sterilize the razor/pruner/scissors to avoid infecting the plant, which will extend the recovery time or affect its growth. To cut, locate the stem above the fifth node and cut it precisely. 

What to do after topping 

Immediately after the cut, the plant goes into a state of confusion as it tries to figure out what has happened. Once it figures it out, it sends recovery hormones (jasmonic acid) and other growth hormones to the injured area. The focus on the area allows for rapid recovery (1 to 7 days). The concentration of growth hormones and nutrients in the area also boosts the growth of the two new main shoots nearby. Some plants may experience stunted growth after topping, but the issue is corrected soon after

Observe

During the plants’ recovery stage, ensure you keep an eye on them and note down any issues. Provide the plants with optimum nutrients, light, and water. 

Subsequent topping

A cannabis plant can be topped one to six times, depending on the cultivator’s preference. Each procedure produces double the number of shoots. For example, if you top 2 main shoots, you end up with four main shoots. Topping the 4 will create 8 main shoots, and so forth. 

If you want to perform subsequent topping, give the plant a couple of weeks to recover from the previous topping. Ensure to top above the 2nd or 3rd node to allow the branches to grow sturdy first.

Prune 

Once the plant begins to grow laterally, it is likely to become bushy, which may limit sufficient light penetration. Pruning removes the unhealthy and dead plant material, allowing for bigger and healthier buds. It also facilitates free airflow within the plant, which keeps out pathogens and eliminates the reproduction of fungi, such as powdery mildew. While pruning, take the chance to thoroughly inspect your plants to identify issues such as nutrient deficiencies, pests, diseases, and soil PH. 

Pruning cannabis plants

Pruning is done in the vegetative stage, as the plant grows bushier. This stops as the plant approaches the flowering stage since it can affect the overall bud quality. Here is how to prune your cannabis plants

You will need sterilized scissors/snips for leaves and small branches and heavy-duty pruners/loppers for large branches. 

Step 1: take out the large branches at the bottom. They are less likely to receive enough light to produce quality buds. By removing these, you create space for free airflow while allowing yourself to work on the smaller branches and leaves.

Step 2: look out for branches in the middle that are blocked out from receiving sufficient light in accordance with the grow light setup. 

Step 3: remove underdeveloped, discolored, and dying leaves and small branches. 

Fimming 

Fimming is a technique similar to topping that involves cutting a large portion of the main shoot (usually 75%). Short for ‘fuck I missed,’ this training method results from a failed topping attempt. It is more complicated compared to topping, but when properly executed, it produces between 3 to 8 new stalks. This creates a bushy plant with numerous branches and multiple bud sites. 

How to fim cannabis plants

You will need scissors or a razor blade for this exercise. Some cultivators prefer a curved razor blade over a straight one or a pair of scissors as it cuts the plant at an angle, redirecting the plant’s new growth sideways. Either way, ensure the cutting apparatus is sterile as infections can be hard to handle, especially when the plant is dealing with the stress of being fimmed. 

The right time to conduct fimming is when the plants have four or more nodes with sturdy branches and leaves. The results will be dependent on the accuracy of the cut and the level of expertise of the cultivator. The aim of fimming plants is to produce an evenly distributed canopy for maximum light penetration and high yields. 

Step 1: Select your plant’s main shoot above the 4th node.

Step 2: pull back the small leaves around the main shoot and hold it between the index finger and the thumb.

Step 3: estimate around three quarters/75% of the shoot and make a single, clean cut using sharp scissors or a razor blade. 

Step 4: If you want more lateral growth and a bushier plant, repeat the fimming technique on other tips. 

Fimming vs. topping 

Here is a highlight of the differences between fimming and topping

Fimming Topping 
Cuts 75% of the main shootTakes out the entire main shoot
Each cut produces 3 to 8 new stalks Each cut produces 2 new stalks
Less traumatic to the plant as it gets to keep part of the technique. Recovery is easier on the plantTaking the entire shoot 

Best strains for topping

Topping works best with strains that tend to stretch vertically, such as Sativas and Sativa-dominant varieties. Indica strains are naturally short, sturdy, and bushy. This makes them ideal for other training techniques, such as LST, SCrOG, and SOG. Topping helps to manage the height while guaranteeing higher yields.

 Autoflowers grow from seed to harvest within 12 to 14 weeks. Cutting off the main shoot will require the plant to take some days to recover from the shock. This is precious time that the plant can use to grow exponentially for better yields. This, however, does not mean that it is not possible to top Indica plants or autoflowers. When expertly done on healthy plants, topping promises impressive results. Below are the top 6 strains that respond well to topping.

Strain nameGenetics THCCBDFlowering timeExpected yield before topping
White WidowSativa dominant26%Less than 1%7 to 9 weeks450–500g/m²  550–600g/plant.
Skywalker OGIndica dominant 20% to 30%1%9 weeks500-600g/m²  700-800g/plant
Blue DreamSativa dominant 15% to 27%2%9 to 10 weeks450-550g/m²  550-600g/plant
Amnesia HazeSativa dominant 23% to 25%Less than 1%10 to 11 weeks550-600g/m²  700-800g/plant
Northern LightsIndica dominant16% to21%Less than 1%6 to 8 weeks500-550g/m²  600-650g/plant

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