Cutting Medicinal plants: Topping & Fimming

By sacrificing a part of the plant early in its life, one can get a greater number of tops and therefore more colas – but how does this work? Which is the better method for training your plants? Read on to learn about the pros and cons of each method and their suitability for various growers.

What Does Topping Mean?

Topping is the process of pruning the growing tip of the main stem of a medicinal plant. This is perhaps the most common HST or high stress training technique applied by both indoor and outdoor growers. Medicinal plants growing naturally will typically take on a Christmas tree structure; One dominant, main central cola and multiple sets of side branches. All plant parts receiving a share of sunlight at some stage during the day as the sun traverses the sky.

In contrast, indoor medicinal plants receive illumination from a stationary grow lamp positioned above. This makes naturally-shaped plants inefficient to crop indoors, unless you cultivate in large numbers using the SOG or Sea of Green method. Topping is the method of choice for pro growers to increase yields. It is also favoured by home growers that want to fill out their grow space with a handful of plants, rather than pack in as many as possible.

Removing the terminal bud will encourage the development of two new main colas and promote growth of the lower, secondary branches. The aim is to invert the Christmas tree shape to allow more light penetration. Growth hormone is diffused to all of the shoots once the apical bud’s dominance is removed. Branchy, low-profile plants are more desirable to every grower. Indoors, vertical space is often at a premium and outdoors, bushes are stealthier than tall trees. Topping is a great technique to take control of the plants canopy. 

What Does Fimming (FIM) Mean?

Fimming, from the acronym FIM is a term used to refer to a specific trimming or pruning method used on medicinal plants during their growth stage. Essentially, fimming is a way to train the plant to grow more of the valuable compounds.

Fimming is very similar to topping a plant. The method encourages the medicinal plant to grow shorter and bushier. It also pushes the plant to create two heads instead of a singular head.

Fimming creates far more lateral branching on the plant. Growers perform fimming by pinching off the plant’s new growth or by using a sharp knife or trimmers to prune away the new growth. Great care must be taken to make sure that the pruners, knife, or the grower’s fingertips are sterile so that no infections are inadvertently transferred to the plant during the fimming process.

Topping vs Fimming Medicinal Plants

Topping medicinal plants is a technique where you cut the central apex of the plant off to help encourage lateral growth. 

Topping works on any number of plants, not just medicinal plants, but when employed, it works the same way and achieves the same goal: topping off the plant to force lateral growth and prevent auxin production. 

When topped, your medicinal plants will force energy into the multiple nodes (or branches) it has early on. This will force them to grow thicker and stronger. You want this because otherwise they grow too tall and too thin.   

Fimming is a technique similar to topping, one that requires a cut near the top of the plant, on the central stem or apex. It is used as a slightly less traumatic technique on plants. 

Think of it as trimming your hair rather than shaving your head. With fimming, you can encourage bushy growth in your plant and increase your cola yields. Fimming is considered more of a training technique. It forces more lateral branch development, or outward growth, and more flowers.  

The funny thing is, this wasn't an official technique used by professional growers for a long time. It was actually an accident that stemmed (no pun intended) from a grower applying the topping technique incorrectly and giving a quick trim rather than a full snip.

 The result was a bushy plant with better yields.

Both of these techniques cause the chemical balance of the plant to change. When we break or remove parts of the plant, it is considered a high-stress training technique, or HST. If you employ an HST, you should give your plant an extra week in its grow schedule to recover.

If You Choose Topping

  • Removes the top part of the plant between nodes.
  • Creates 2 main colas at a time at the top of the plant.
  • Topping is stressful for a young plant and recovery time is longer than that of a plant that has been FIMmed.
  • Topping can be performed to reduce the vertical height of a plant during its vegetative cycle.
  • Forms a large, bushy structure that will require less structural support than FIMmed plants.
  • Newly-formed colas are evenly spaced.

If You Choose Fimming

  • Removes the newest growth without cutting between the nodes.
  • Fimming is less traumatic to the plant, allowing for quicker recovery time.
  • Creates four main colas at once, whereas topping only creates two.
  • Perfect for growers with limited space, as the plant will begin to grow laterally instead of only vertically.


If you’re looking to increase yield or just want to keep your girls short, then you should definitely consider incorporating topping and/or fimming into your gardening style. These techniques can help you a lot.

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