Topping vs. Fimming Cannabis Plants: Exploring Low-Stress Training Techniques for Enhanced Yields

Cannabis cultivation is an evolving science, and growers are constantly discovering new techniques to improve yield, bud quality, and overall plant health. Among these methods, topping and fimming are two widely-used approaches that manipulate plant structure by disrupting its natural growth patterns. Both techniques aim to improve yields and create more manageable canopies but differ in terms of precision, plant stress, and recovery time. Alongside these methods, various other Low-Stress Training (LST) techniques like the Screen of Green (SCROG) and Low-Stress Training (LST) itself offer more advanced options for growers seeking to optimize light exposure and bud development.

This article explores the science behind topping and fimming, analyzes their effects on the plant’s hormonal balance, and discusses how these techniques influence growth patterns and canopy structure. It also delves into other training techniques, including LST and SCROG, to provide a comprehensive guide on how to maximize cannabis yields. Practical tips for indoor and outdoor growing, considerations for different strains and growing conditions, and advanced methods for experienced growers will also be covered.

Understanding Topping: How It Works

Topping is a cannabis training technique used to break apical dominance. Apical dominance refers to the plant’s natural tendency to focus growth on its central stem, or apex. This vertical growth is governed by auxins, a class of plant hormones produced in the apex that suppresses lateral growth, keeping the plant tall and slender. Topping involves cutting off the plant’s topmost growth, usually just above a node, to force the plant to redistribute its growth hormones, particularly cytokinins, which promote lateral branching. By doing this, the plant develops multiple main colas, resulting in a bushier structure and more even canopy.

Science Behind Topping

Cannabis plants prioritize vertical growth to compete for sunlight in their natural environment. Auxins accumulate in the top part of the plant, suppressing the development of side branches. When the top of the plant is removed through topping, the level of auxins drops, and cytokinin levels rise, promoting cell division in the lateral buds.

In practical terms, after topping, the energy that would have gone into upward growth is redirected into the side branches, which will grow more vigorously. This creates a more even canopy, allowing for better light distribution across all bud sites. As a result, multiple main colas can develop, which may increase overall yields.

Step-by-Step Guide to Topping

1. Timing: Topping should be done after the plant has developed 4–6 nodes. The plant should be healthy and growing vigorously to ensure a smooth recovery.
2. Tools: Use sharp, sterilized scissors or pruning shears to make a clean cut.
3. Cutting Point: Identify the topmost growth just above a node, typically where two new branches are about to form. Make the cut just above this point.
4. Aftercare: After topping, monitor the plant for any signs of stress. Some stunting in growth is normal for the first few days as the plant recovers. Ensure the plant has adequate nutrients and light during this period to promote healthy growth.

Advantages of Topping

• Increased Yield: By promoting the growth of multiple colas, topping can lead to higher yields compared to untopped plants, which usually develop one large central cola.
• Improved Canopy Management: Topping creates a more even canopy, which allows for better light penetration to lower parts of the plant, improving overall bud development.
• Stronger Plants: Topped plants tend to develop stronger stems and branches, which can support heavier bud sites.

Disadvantages of Topping

• Plant Stress: Topping is considered a high-stress training technique. Removing the apex shocks the plant, which can temporarily slow growth as the plant recovers.
• Increased Recovery Time: Depending on the plant’s health and growing conditions, it may take several days to a week for the plant to recover fully and resume vigorous growth.

Understanding Fimming: A Less Precise Technique

Fimming is a variation of topping that involves cutting approximately 75% of the plant’s new growth at the apex rather than fully removing it. The goal of fimming is to encourage the development of more than two new colas. While topping usually results in two main colas, fimming can produce four or more. The term “FIM” comes from the phrase “F***, I Missed,” originating from growers who accidentally missed the topping and it stuck around because it kinda works!

Science Behind Fimming

Like topping, fimming disrupts the flow of auxins from the apex to the rest of the plant. However, because the apex is not completely removed, some vertical growth continues, albeit at a reduced rate. This partial disruption of apical dominance allows multiple colas to form, but the canopy structure may be less predictable and less symmetrical compared to topping.

Cytokinins also play a role in fimming, as they stimulate cell division and growth in lateral branches. By fimming, growers increase cytokinin levels in the lower parts of the plant, encouraging a bushier and denser plant structure.

Step-by-Step Guide to Fimming

1. Timing: Like topping, fimming is best performed when the plant has 4–6 nodes.
2. Tools: Use sterilized scissors, but the cut does not need to be as precise as with topping.
3. Cutting Point: Instead of cutting just above a node, cut approximately 75% of the way through the topmost new growth.
4. Aftercare: As with topping, monitor the plant for signs of stress. The plant will take some time to recover, but fimming generally induces less stress than topping.

Advantages of Fimming

• Multiple Colas: Fimming can produce more than two colas, often resulting in four or more.
• Faster Recovery: Fimming is less stressful than topping, leading to a shorter recovery period.
• Less Precision Required: Fimming does not require as much precision as topping, making it an easier technique for beginners.

Disadvantages of Fimming

• Unpredictable Results: The growth patterns resulting from fimming can be less uniform than those achieved through topping. This can lead to uneven canopies and a more unpredictable plant structure.
• Lower Yield Predictability: While fimming can produce more colas, the distribution of energy between these colas may not be as efficient as topping, potentially leading to less optimal yields.

Comparing Topping and Fimming: Hormonal Balance and Growth Patterns

Both topping and fimming impact the plant’s hormonal balance, primarily by disrupting apical dominance through the manipulation of auxins and cytokinins. The major difference between the two techniques is the extent of disruption.

Hormonal Impact

• Topping: By completely removing the apex, topping dramatically reduces auxin levels in the plant, promoting a significant increase in cytokinin levels, which encourages the growth of lateral branches. This leads to a more controlled and predictable bushy structure with multiple colas.
• Fimming: Fimming only partially disrupts auxin production, resulting in a less dramatic shift in hormone balance. This causes a broader distribution of growth across more colas, but the growth pattern is less controlled and can lead to unpredictable outcomes.

Growth Patterns and Canopy Structure

• Topping: Topping typically leads to a symmetrical and controlled growth pattern. The plant will produce two main colas, and with additional training, these can be further multiplied.
• Fimming: Fimming produces more colas than topping but often results in a bushier and less symmetrical canopy. This can lead to inconsistent light distribution, which may affect bud quality in lower branches.

Which Technique is Better?

The choice between topping and fimming largely depends on the grower’s goals and growing environment:

• For Even Canopies: Topping is the better choice for growers who want to create a flat, even canopy for better light distribution and more predictable results.
• For More Colas: Fimming may be preferable for growers looking to maximize the number of colas without worrying about symmetry or uniformity in the plant’s structure.

Low-Stress Training (LST): A Gentle Approach to Canopy Management

Low-Stress Training (LST) is a method of training cannabis plants that involves gently bending and tying down branches to manipulate the plant’s shape without removing any growth. LST allows growers to control the plant’s height and promote lateral growth without the stress caused by cutting. This technique is especially useful for indoor growers with limited vertical space.

Science Behind LST

LST works by physically altering the plant’s shape to disrupt apical dominance without cutting the plant. By bending the main stem and tying it down, the grower lowers the apex below the level of other branches. This redistribution of auxins encourages lateral branches to grow more vigorously, leading to a more bushy structure with multiple colas. Unlike topping or fimming, LST does not involve a significant hormonal shock to the plant, making it a low-stress option.

Step-by-Step Guide to LST

1. Timing: LST can be started early in the plant’s life, usually after it has developed 3–4 nodes.
2. Tools: Use soft plant ties or string to gently bend and secure branches in place.
3. Tying Down: Start by bending the main stem down and tying it to the side of the pot or grow space. Continue bending and tying down side branches as they grow.
4. Ongoing Maintenance: Regularly adjust the ties as the plant grows to maintain a low, even canopy.

Advantages of LST

• Minimal Stress: LST does not involve cutting the plant, so it causes little to no stress.
• Improved Light Distribution: By creating a wider and flatter canopy, LST allows for better light penetration to lower bud sites, improving overall yield and bud quality.
• Control Over Height: LST is an excellent way to control plant height, especially in indoor grows where vertical space is limited.

Disadvantages of LST

• Labor Intensive: LST requires frequent adjustments and maintenance as the plant grows.
• Slower Results: LST does not produce as dramatic an increase in colas as topping or fimming, so it may take longer to see results.

Screen of Green (SCROG): Maximizing Light Exposure

The Screen of Green (SCROG) technique involves placing a screen or net above the cannabis plants and training the branches through the screen as they grow. The goal of SCROG is to create an even canopy by spreading out the plant’s branches, ensuring that all bud sites receive equal light exposure.

Science Behind SCROG

SCROG works by physically altering the plant’s growth pattern and redistributing light more evenly across the entire canopy. By weaving the branches through the screen, growers can spread out the plant’s growth horizontally rather than vertically. This allows for better light penetration to all bud sites and reduces the risk of shadowed or underdeveloped buds.

Step-by-Step Guide to SCROG

1. Set Up the Screen: Place a screen or net over the plant when it is still in the early stages of vegetative growth.
2. Training Branches: As the plant grows, gently weave the branches through the screen, spreading them out to create a flat, even canopy.
3. Ongoing Maintenance: Continue adjusting the branches and tucking them through the screen as the plant grows to maintain an even canopy.

Advantages of SCROG

• Maximized Light Exposure: SCROG ensures that all bud sites receive equal light, leading to more even bud development.
• Increased Yield: By creating an even canopy, SCROG can significantly increase yields in both indoor and outdoor grows.
• Control Over Canopy: SCROG allows growers to control the plant’s height and shape, making it ideal for indoor grows with limited vertical space.

Disadvantages of SCROG

• Labor Intensive: Like LST, SCROG requires regular maintenance and adjustments to keep the canopy even.
• Requires a Longer Veg Phase: SCROG is most effective when the plant is allowed to spend more time in the vegetative phase to fill out the screen, which can extend the overall grow time.

Combining Topping, Fimming, LST, and SCROG for Maximum Yields

Experienced growers often combine multiple training techniques to optimize their results. By strategically topping or fimming plants and then applying LST or SCROG, growers can create large, bushy plants with multiple colas and maximized light exposure. These techniques can be particularly effective when used in conjunction with each other, as they offer a balance between high-stress and low-stress training.

Topping or Fimming Followed by LST

1. Topping/Fimming: Start by topping or fimming the plant after it has developed 4–6 nodes.
2. Recovery: Allow the plant to recover and develop new colas.
3. LST: Once the new branches have grown, begin bending and tying them down to create an even, low canopy.
4. Results: This combination promotes multiple colas while keeping the plant low and wide, improving light penetration and airflow.

SCROG with Fimming

1. Fimming: Fim the plant after it has developed 4–6 nodes.
2. Screen Placement: Place a screen over the plant and begin training the branches through it as they grow.
3. Maintenance: Continue weaving the branches through the screen to create an even canopy.
4. Results: This method is ideal for indoor grows with limited vertical space, as it maximizes light exposure and encourages the growth of multiple colas.

Advanced Techniques: Defoliation and Mainlining

In addition to topping, fimming, LST, and SCROG, advanced growers can incorporate defoliation and mainlining into their training routines to further control plant structure and maximize yields.

Defoliation

Defoliation involves selectively removing large fan leaves to improve light penetration and airflow within the plant’s canopy. This technique can be particularly useful when combined with LST or SCROG, as it helps prevent lower bud sites from being shaded by upper leaves.

• Step-by-Step: Remove large fan leaves that block light from reaching lower bud sites. Be careful not to remove too many leaves at once, as this can stress the plant.
• Benefits: Defoliation improves light penetration, reduces the risk of mold and mildew, and encourages the plant to focus its energy on bud development.

Mainlining

Mainlining, also known as manifold training, involves repeatedly topping the plant to create a symmetrical structure with multiple main colas. This technique is often used in combination with SCROG or LST to further optimize the plant’s shape and maximize yield.

• Step-by-Step: Start by topping the plant after the third node. Allow the plant to recover and then top the two new main stems again after they develop. Continue this process until the plant has developed a symmetrical manifold structure.
• Benefits: Mainlining creates a balanced plant with equal energy distribution, leading to uniform bud development and higher yields.

Environmental Considerations: How Conditions Affect Training Techniques

Humidity and Light Levels

Training techniques like topping, fimming, LST, and SCROG are most effective when environmental conditions are optimized. High humidity can increase the risk of mold and mildew, especially in dense, bushy plants. Techniques like defoliation and SCROG help improve airflow, reducing this risk. Proper light levels are also crucial for training success. Ensuring that all parts of the plant receive adequate light will lead to better bud development and higher yields.

Temperature

Maintaining a stable temperature is important, particularly when using high-stress techniques like topping and fimming. Temperature fluctuations can stress plants, slowing recovery times and negatively impacting yields. Keeping the grow space within the optimal temperature range (around 70-85°F) will help ensure healthy growth and successful training outcomes.

Examples of Use

Example 1: Indoor Grow with Topping and LST

An experienced indoor grower with limited vertical space used topping followed by LST to create a low-profile canopy. By topping early and tying down branches, the grower was able to maximize light exposure and achieve a high yield from multiple colas without the plant outgrowing its space.

Example 2: Outdoor SCROG with Fimming

An outdoor grower combined fimming with SCROG to create a bushy, low-profile plant with multiple colas. By training the branches through a screen, the grower maximized light exposure and airflow, resulting in a high yield and healthy plants with minimal pest issues.

Conclusion

Topping and fimming are highly effective techniques for increasing cannabis yields by disrupting apical dominance and promoting lateral growth. While topping provides more predictable results with an even canopy, fimming offers the potential for more colas and a bushier plant structure. Combining these techniques with complementary training methods like LST and SCROG can further optimize light exposure, airflow, and yield potential. For advanced growers, incorporating additional techniques like defoliation and mainlining offers even greater control over plant structure and productivity.

Ultimately, the key to success lies in understanding the science behind these techniques and applying them strategically based on the specific growing environment, strain, and space limitations. By mastering these methods, growers can achieve impressive yields, healthier plants, and higher-quality buds.