Grow GuideTopping vs Fimming: Which Cannabis Training Technique Should You Use?
Mar
Topping and fimming are two similar yet distinct techniques to guide your plant’s structure. They are the twin pillars of high-stress training. In this guide, we’ll show you how each one works, what it does to your plant, and help you decide which technique fits your grow setup.
What is Apical Dominance in Cannabis?
Apical dominance is a hormone-driven process through which the apex of the cannabis plant shoots above the rest to make one main cola. This dominant stem produces auxins, a plant hormone that slows the growth of side branches.
When you cut or damage that dominant tip, you instantly halt the flow of those growth-suppressing hormones. This shock causes the plant to redistribute its energy. The plant instantly pivots from vertical growth to lateral branching.
Both topping and fimming rely on disrupting this “apical dominance” to trigger bushier growth. Their critical difference simply lies in how much of the top growth you remove.
Is Fimming Better Than Topping?
What Is Topping
Topping is a clean, definitive cut that completely removes the newest growth tip of the apical stem. This results in the two shoots directly beneath the cut becoming the new main stems. It is the most common and effective technique for achieving a flat, balanced canopy.
When Should Topping Be Done
Only top your cannabis plant once it has truly settled in and is growing strong. A helpful guideline is to wait until your plant shows at least four to six true nodes. You want your plant to be vibrant and tough enough to handle this intentional stress.
What Is the Method of Topping
The method is straightforward and must be precise to minimize stress and prevent infection:
- Identify the top node—usually just above the 4th or 5th from the bottom.
- Use sterilized scissors to prevent infections.
- Snip just above that node.
- Give your plant a few days to recover.
What Does Topping Do for Cannabis
Topping leads to several benefits.
- With more colas springing up, you have the potential for more bud sites, leading to higher yields.
- There is improved canopy distribution from the new flat top structure that helps manage vertical stretch in space-limited grow rooms.
- Topping optimizes light exposure to multiple bud sites that would have been obscured by the shade of the main stalk.
Downsides of Topping
While highly effective, topping has some drawbacks.
- Higher initial stress from complete snipping of the dominant tip requires longer recovery periods, which may slow down the plant cycle.
- The higher stress levels mean that topping can only be done on a completely healthy plant with the ability to bounce back in time.
- Due to the longer recovery needed, topping is not recommended for short-cycle strains like autoflowers.
What Is Fimming
The origin of the name “fimming” is said to come from a grower’s exclamation, “F***, I missed!” a small amount of new growth during an attempted topping. So, in real practice, fimming involves removing most, but not all, of the latest growth at the tip of a plant.
Pro Grow Tip : Many growers FIM between week 3 – 5 of Veg. Wait until the plants have at least 4 to 6 nodes.
This method can lead to a more bushy plant structure with multiple new shoots developing from the cut area.
How to fim properly
The technique is simple but requires a gentle touch.
- Isolate the New Growth: Gently pinch the smallest, newest leaves right at the crown of the plant—the very top.
- Trim Most of It: Use sterilized scissors or your fingernail to snip off the top three-quarters of the new shoot. You are aiming to damage the meristem without entirely removing the whole node.
- Leave a Quarter: A small ring or skirt of the newest leaf base should remain. This will often split into multiple new tops.
How many nodes before fimming
Fimming should be done early in the plant’s life, generally when the plant has about 3 to 5 established nodes during the active vegetative growth stage.
Benefits of fimming
Fimming offers several key advantages, particularly for the grower who prefers lower overall stress.
- Because the main stem is not completely severed, the plant experiences less overall stress and tends to recover significantly faster compared to topping.
- The plant often reacts to the partial damage by producing 3 to 8 new tops from the single cut site. There is a significantly higher potential number of colas than topping.
- It’s a lighter form of pruning than topping, making it a good choice for slightly less vigorous or slightly stressed plants.
Drawbacks of fimming
Fimming has its own unique challenges that growers must anticipate.
- Unlike topping’s clean split, the results of fimming are often unpredictable. You might get anywhere from three to seven tops, or eight at the most.
- The resulting tops can be uneven in growth vigor, requiring more selective pruning or low-stress training (LST) to manage a flat canopy.
- Getting the perfect 80% cut takes practice. Miss too little and it won’t work. Miss too much, and it becomes a more stressful topping.
Choosing the Right Technique for Your Setup
The best training method for your garden depends entirely on your physical growing environment and the genetic makeup of your chosen strain.
Small Indoor Grows
These environments, especially those using powerful LED grow lights, benefit immensely from topping. The goal is to create a flat, even canopy (known as a Sea of Green or Screen of Green), which ensures every square inch of the canopy gets equal, optimal light.
Outdoor Growers or Large-Tent Setups
If you’re not worried about height, fimming is usually the way to go. This technique helps develop a multi-stemmed structure that can support more buds for a bigger yield.
Sativa vs Indica Strain Vigor
Sativa dominant strains are naturally leggy and tall. Their structure favours repeated topping to manage their height. Indicas on the other hand are more bushy and prefer a single fimming or topping to boost their already compact form.
Autoflower Caution
Autoflowering cannabis strains are extremely sensitive to stress due to their time-limited vegetative phase. If you train an autoflower, only attempt light-fimming early—ideally around the third node—and avoid topping altogether unless you are an experienced grower with a highly vigorous plant.
FAQs
Can you top or fim autoflowers?
You can lightly fim an autoflower once it’s grown three solid nodes. However, while gentler than topping, it can still interrupt the rhythm of an already short autoflowering growth cycle. Topping is generally discouraged for autos, as we have already seen.
How many times can you top?
It is possible to top a photoperiod cannabis plant multiple times during its vegetative stage. Many growers use a technique called “mainlining,” which involves topping the plant multiple times to create 8, 16, or even 32 uniform main colas.
When is it too late to top your plant?
It is too late to top once your plant has entered the flowering stage. Pruning the plant during flowering will only result in a loss of essential bud sites and could severely stress the plant. It can even cause hermaphroditism or significantly reduced yields.
Does topping delay flowering?
Yes, topping does delay flowering slightly. The period of stress and recovery after a topping cut can add 5 to 10 days to the plant’s vegetative phase. This is a deliberate delay, as the grower is sacrificing a little time to achieve a much higher overall yield.
Can you combine both?
Absolutely YES! Many growers top the plant initially to create two main stems. Later on, they fim the resulting side branches once they’re established. This allows you to combine the structural symmetry of topping with the high-yield branching potential of fimming.
Which technique is better for beginners?
Fimming tends to be less stressful for the plant but requires advanced low-stress training for its uneven canopy. Topping, on the other hand, is more precise for beginners but carries a higher risk of stress.
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