Fimming Cannabis: Everything You Need to Know

Adam Parsons

Cannabis Journalist & Staff Writer at Zamnesia

Adam Parsons

13 June 2019

The objective is to promote multiple main colas and make plants bushier. Fimming might not be the neatest pruning for yield method, but it is proven to be effective. By the end of this grow guide, you will be able to experiment with the FIM method yourself. We recommend topping and fimming at least a couple of plants in the grow op.

WHEN TO FIM

As is the case with virtually all pruning and training for high yield methods, it’s best to FIM during vegetative growth. Whenever you clip parts away from your cannabis plants, they will be stressed and will need some time to recover from the pruning. This is the primary reason to prune prior to the onset of flowering.

In the US it’s common for growers to pinch off the tops from infant cannabis plants barely out of the seedling phase. Although this ensures plants will grow like bushes, it needs to be followed by LST and/or a ScrOG. If you have got the hands-on experience in all the above techniques, go for it. But for the novice grower or growers without the time for a lengthy vegetative cycle, this is not ideal.

European cannabis growers prefer to wait until plants are around 30cm tall before applying pruning for yield methods. Allowing plants 3-4 weeks of vegetative growth to get to a decent size and develop means they will recover faster. Fimming can be applied anytime in the vegetative phase. No need to rush. Being patient in the early plant lifecycle can save you time later.

HOW TO FIM

To apply the FIM method couldn’t be easier. You have a choice between pinching and snipping. It all comes down to what is the most comfortable style for the grower. If you prefer to prune with scissors, then stick with your sterile clippers.

It’s best to keep in mind that Fimming originated from an instance of inaccurate plant topping. Fimming is the process of removing approximately 75% of the tip from the main shoot. Pinching off the area between the fingertips allows more room for error and often results in a more successful FIM.

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Just make sure to FIM during vegetative growth. Precisely when to FIM is at the grower's discretion. Take note plants will need about 1 week to recover and for the new growth to develop. Expect an ugly sight in the aftermath. A set of torn leaves if you pinch and a Medusa head of colas are typical.

Topping a cannabis plant neatly with scissors by completely removing the tip from the main shoot gives rise to two new main colas. Fimming usually gives rise to 4 new main colas. These numbers can vary slightly depending on strain and how much of the main stem was removed. Furthermore, the FIM will also encourage the plant to bush out and fill lateral grow space too.

BENEFITS OF FIMMING

Fimming can be even more effective than topping for increasing the yield of cannabis plants. Obviously, 4 main shoots are more than 2. Furthermore, fimming seems to effect the auxin distribution in marijuana even more profoundly than topping. Plants that have been fimmed not only develop a greater number of tops but also branch more abundantly.

Fimming is a very flexible pruning for yield method and can be blended into a mix of other training and pruning techniques for maximum yield. A FIM crop of a handful of cannabis plants combined with a ScrOG can be just as productive as a SOG with 2-3 times the number of plants.

An early applied FIM, as is preferred by US growers, is tremendously effective at transforming plants of any strain into squat branchy bushes. Plus the FIM method can be applied multiple times until the grower is satisfied with the density of the weed bush.

The greatest benefit of the FIM method is that it's forgiving. Accuracy is not the primary objective. A sloppy Topping can often turn out to be a fantastic multi-cola FIM.

DISADVANTAGES OF FIMMING

Fimming is a technique that does not lend itself to Autoflowering cannabis varieties. The stress of pruning the main stem and the associated recovery time will stunt the growth of Autos. On average growers using the FIM method will keep plants in vegetative growth for 4-6 weeks. That’s just too long for an Auto grower to wait.

Later in the bloom phase in the absence of a ScrOG, it can be difficult to keep the grow space orderly. If you decide to FIM as a standalone high yield method, it’s probably best to stake plants for support. All those heavy colas can make marijuana bushes top heavy with bud, but this is a good kind of problem.