Main-lining Cannabis Plants To Increase Yields

High stress training is known for improving yields, but what is main-lining? This advanced technique is used by growers to maximise efficiency in the grow room and we want to show you how. This guide teaches you the ins and outs of safely main-lining cannabis plants so you can achieve larger harvests in a limited amount of space.

What Is Cannabis Main-lining?

Main-lining is used by many growers these days, with the intention to produce the highest yields possible in a small area. Height restrictions are a big deciding factor when it comes to main-lining, although the technique is just as viable when vertical space isn't an issue.

The process of main-lining takes time and patience. Main-lining is a gradual process and requires you to wait for the plant to heal before proceeding to the next stage. It is important that we do not induce too much stress at one time or the plant may suffer and take longer to recover.

Main-lining involves fairly rigorous training and tends to be used along side other training methods such as topping and LST (low stress training) to achieve the desired shape and size. The goal is to break the plant's apical dominance (usually one main cola) and even out the canopy so we end up with a flatter, bushier plant that grows wide instead of tall, with lots of top buds.

The Pros and Cons Of Main-lining?

There are loads of benefits to performing main-lining, however the main reason growers use this method is without a doubt to improve yields. Aside from more bud, main-lining done correctly can help to strengthen a cannabis plant, making it more resilient against problems later on such as pests or mold.

Of course, there are always some risks involved, so make sure you take it slow and do not rush the process. First-time growers may want to hold off using main-lining until they have a couple of grows behind their back, along with some understanding of how stress training works.

Lost Coast OG / Organic / Mainlining /

Once you're comfortable handling your plants, know how they perform and are effectively meeting their demands, you may want to start thinking about how to further improve yields. Otherwise, you may have too much to manage and possibly end up with smaller harvests than expected.

How to Perform Main-lining

Main-lining can be performed in steps. It is usually applied in stages during the vegetative cycle to give the plant a balanced, symmetrical structure before the flowering phase. After main-lining, additional training during the pre-flowering stage can help the plant focus more energy towards the canopy.

Step 1: Growth

In order to begin training, a cannabis plant should first be in the healthiest state possible. If the plant is already suffering from deficiencies or other problems, stress training may not be the wisest idea. There is a risk of stunting growth and your grow cycle could be extended.

Main-lining can begin once a cannabis plant has at least 5-6 nodes along the main stem (normally about 3 weeks from seed). Starting any earlier than this may cause too much stress for the plant to handle, and could potentially stunt growth. We want to make sure the plant has enough time to develop a strong root structure for support and repair once the training does start.

Step 2: Topping

Topping is actually very easy to perform and simply requires you to snip off the new growth emerging at the top of the main stem. This results in a 'split' of the main cola as the plant directs it's energy to the two branches below the cut, which develop into two main colas. These branches can also be topped to leave 4 branches, and so on. The process can be repeated over and over until the desired number of tops has been achieved.

For main-lining, plants should be topped down to just above the 3rd node, making sure to leave a stump. That means removing everything above this point. After each topping, you need to wait until the new branches are well established before topping further (have at least 2-3 nodes). If you are still unsure about topping, why not check out our guide on high stress training (HST)?

Tip: Tops can be used for cloning if you do not want to throw them away.

Step 3: Trimming

After the plant is topped above the 3rd node, we must also remove some growth below it. Leaves are very important at this stage in a cannabis plant's life so make sure to leave some otherwise we may slow growth.

The lower shoots (1st and 2nd node) can be removed so the plant starts to direct its energy to the remaining 2 branches at the 3rd node. Once these two branches have grown out and have 2-3 nodes, they can be topped again. If you like, the lower nodes can be also be trimmed again.

Step 4: LST (low stress training)

The next step is to apply some low stress training (LST) to prevent the plant from returning to its vertical positioning. LST helps to guide the branches horizontally. Both sides of the plant need to be the same height to encourage even growth across the tops. If one side is higher, the plant prioritises those top buds and they will grow bigger than the other side.

Low stress training involves gently bending and tying branches down. In the case of main-lining, this would mean directing them outwards and away from each other in a symmetrical fashion. This allows the tops to grow upwards and make fair use of the light above them.

Tip: Tie branches down using soft ties or thick string that doesn't damage the outer walls of the branches. 

Step 5: Additional Training

Depending on how big you want your plants to get, a 3rd topping can be performed, with the result of 8 colas. During this time, be sure to continuously adjust and add more ties to keep the plant even across the canopy.

Pruning/Defoliation - Once your plants are fully mainlined, additional training can be applied. Pruning or defoliation can take place in the first 2-3 weeks of the flowering period as the plant matures into a strong, structured cultivar. Any bud sites or leaves low down that are not receiving enough light can be removed to allow the tops more energy. Just remember not to cut off too many leaves; the plant still needs them to photosynthesise.

Summary of Main-lining Technique

Let's summarize the process of main-lining so you can easily follow along.

Steps To Perform Main-lining:

1. Wait until your plant has 5 - 6 nodes.
2. Sterilize your clippers or sharp scissors.
3. Top the plant down to the 3rd node.
4. Working your way from the bottom, cut off the shoots up till the 3rd node. Make sure you leave at least 1 or 2 sets of fan leaves.
5. Once the plant has 3-4 nodes on the new branches, they can also be topped.
6. Tie down the main 2 branches using LST.
7. Once the plant has recovered and the 4 tops are growing out, they can also be topped.
8. Repeat LST and topping until you have achieved the desired number of tops.

Main-lining by PlainFieldPuff from GrowDiaries.

Conclusion

It can be a daunting task to manipulate your plants so heavily when they are young, but taking that step has the potential to improve your grow significantly. After you successfully train your first cannabis plants, you'll understand the limits and the process becomes much easier. Hopefully your big harvests at the end will make you want to continue experimenting with stress techniques, as they really can do wonders for your garden.

If you found this article useful or have any tips to add about main-lining, feel free to share your thoughts down in the comments section.

External References

Auxin, cytokinin and the control of shoot branching, Annals of Botany, Volume 107, Issue 7 - Dörte Müller, Ottoline Leyser (2011)

Shaping Plant Architechture, Front. Plant Sci. - Thomas, Teichmaan and Merlin Muhr (2015)

Early topping: an alternative to standard topping increases yield in cannabis production. Plant Science Today. - Gaudreau, Sylvain & Missihoun, Tagnon & Germain, Hugo. (2020).

This article was updated November 2020.