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How To Do High Stress Training (HST) On Cannabis

Created by
JoshuaHolt JoshuaHolt
Added 23 October 2020

This guide deals with high stress training. Learn how HST can help you maximise efficiency in your grow space and provide you with higher yields.

High Stress Training Techniques On Cannabis

Manipulating your cannabis plants can be a tough move if you've never done it before. Stressing a perfectly healthy plant can seem counterproductive, but it actually has the potential to improve your grow. This guide explains why and shows you how you can start stressing your plants safely.  

You may have seen some weirdly shaped cultivars before and wondered why growers choose to change the structure of their plants so drastically when there is a potential risk involved. High risk equals high reward so if you play your cards right the results can be more than satisfying.

Fortunately, high stress training techniques don't have to be stressful for you as well. Even though some plants can handle a heavy battering, the most important thing is to take it slow and not expect results too quickly. Manipulating the shape of your cannabis plants should be done with extra care so you don't damage them heavily during the process.

What Is High Stress Training (HST)?

High stress training (HST) is similar to low stress training (LST), but involves more rigorous manipulation. HST can be performed in a number of ways, and is often paired with LST techniques to achieve the desired plant shape and size. Applying high stress techniques usually requires us to cut, bend or break areas of the plant repeatedly, leaving time in between each manipulation for recovery. 

The principal of high stress techniques is to break the apical dominance of the plant, which its understanding of its own height. A cannabis plant concentrates its energy on the highest flower. It does this as a reproductive technique because it has more access to light and it increases the probability of pollen landing.

High Stress Training (HST) Manipulates Plant Shape and Size

Naturally, a cannabis plant will grow one long main stem with branches shooting off in alternating fashion. By preventing the main cola to extended higher and manipulating the lower branches to catch up in height, we allow hormones to be more evenly distributed across the tops of a plant. This creates an even canopy with buds of more or less the same size. Chemical activity increases at the top buds because they receive more light, meaning they can produce more resinous goodness.

The Benefits of HST on Cannabis

If you've ever accidentally bent a branch on one of your plants you may have realised how efficiently it manages to heal itself. Just like the human body, a cannabis plant has a response system that works hard to repair any damages. Often wounds heal to be even stronger than they were before. New, stronger cells grow in the affected areas, usually leaving a scar or deformation.

High Stress Training Strengthens Plants

Plants function in a similar way and are working constantly to keep themselves in a state of balance (homeostasis). Any stress they receive can cause them to adjust to try and fix the problem as quickly as possible. Done in a controlled way, and stress can actually make a cannabis plant sturdier and more robust.

Other than making your plants stronger, there are lots of reasons to experiment with high stress training. We wouldn't be using this technique if there weren't some extremely valid reasons to do so. Let's go over why a grower would apply HST to their cannabis plants.

  • Increases Yield
  • More Top Buds
  • Maximises Space
  • Controls Size
  • Efficient Use Of Light
  • More THC

Is HST safe for my Cannabis Plants?

Remember, we are stressing our plants here, so there is always a risk of something going wrong. Too much stress can kill a plant so it is recommended that HST is applied gradually in the most hygienic way possible. Removing lots of foliage at once or bending too many branches means the plant is more susceptible to infection. Open wounds can be a health risk if the grow area is not completely clean and pest free.

The conditions must also be well maintained so the plant can focus its energy on growing and repairing itself. If there are imbalances with temperature or humidity while you are applying training techniques it could slow the whole process and growth may be heavily stunted due to other problems. Most growers perform training during the vegetative stage and preflowering stage so that plants have plenty of time to heal before full blooming.

High Stress Training Can Be Applied Once A Plant Has 4-5 Nodes

Applying LST and HST is safe to do with most strains of cannabis, but you must follow some simple steps in order to keep things as smooth as possible.

  • Check if your strains can handle stress techniques.
  • Sterilize your equipment before and after every training session.
  • Give the plant time to recover before applying more stress.
  • Keep stable grow room conditions.

How To Perform High Stress Training

In this next section, we want to discuss the ways a cannabis plant can be trained using high stress methods. There isn't one set way to apply stress, and how you proceed depends on your objective, as well as the space you have available. You might be simply trying to control the height of your plant or maybe your goal is to produce more sticky top buds.


Cannabis Defoliation

Defoliation is a technique that involves removing a large amount of leaves growing at the branch internodes. The idea behind this is to reduce the energy spent on maintaining leaves lower on the plant that are not receiving enough light. Removing leaves that are not serving their purpose well can help to direct the plant's energy to the tops where light is most available.

Fan leaves tend to block areas that would favour more exposure. By removing some of the foliage, we allow more light to pass through the canopy to bud sites lower down on the plant. This can prevent excessive stretching as the plant doesn't have to work as hard to 'search' for light. Airflow will be greatly increased too, helping you to control humidity levels around the plant more efficiently.

How To Perform Defoliation:

  1. Start during vegetative phase, working in stages.
  2. Use sharp, sterilized clippers or scissors.
  3. Do not cut off leaves around the tops. Start from the bottom.
  4. Firstly, remove the lowest 20% of the leaves, including fan leaves.
  5. Wait for the plant to recover.
  6. Then, prune areas of the plant that could benefit from more light and airflow. Make sure you do not cut off too many leaves.


Cannabis Topping

The topping technique is commonly used in indoor growing to control plant height. Topping involves snipping off the new growth at the top of the main stem or lateral branches. This allows the side shoots just below the cut to develop into main colas. Those two new colas can be topped again to create four colas. This process can be repeated as many times as you like, provided you give enough time for the plant to heal between each topping.

Topping creates a short and bushy plant with a wide structure. Usually, LST is applied after topping to allow lower branches to reach the same height and eventually even out the canopy with a flat top.

HST by BodyByVio from GrowDiaries.

How To Perform Topping:

  1. Wait until the plant has developed 5 - 6 nodes before topping.
  2. Sterilize your clippers or sharp scissors.
  3. Snip off the new growth right above the two newest shoots, leaving a small stump.
  4. Wait 1 - 2 weeks until the plant has shown solid growth before topping again. Lateral branches can also be topped if you wish.
  5. Repeat until you have the desired amount of colas.


Cannabis FIMing

The FIM, or 'Fuck I Missed' technique is essentially topping gone wrong, but with a surprisingly positive outcome. FIMing takes the same process as topping, but instead of cutting off the whole top shoot of new growth (including the stem), the leaves are shaved above the main stem. This makes recovering from FIMing much faster than topping, as we are not cutting a part off its main circulatory system.

By removing just a portion of the top, upward growth is halted, and the stress forces the plant to grow outwards by developing new shoots. This method can produce 2, and if you're lucky, 4 branches from the FIMmed site.

How To Perform FIMing:

  1. Pinch the top of your cannabis plant with your thumb and forefinger so you can easily cut through the new growth at once.
  2. Using sterilized clippers or scissors, snip between 70 - 80% of the new leaves off in one clean cut. You want to leave around 20%.
  3. Wait 3 - 5 days for new growth to appear.
  4. Repeat on other branches for more colas. 


Cannabis Supercropping

If you've ever grown outdoors you may have experienced cannabis' miraculous ability to fix itself. Strong winds can cause some pretty heavy damage, often bending branches at all kinds of weird angles. The drive to survive gives cannabis plants the ability to rectify kinks and small breaks without too much difficulty, and you'll be amazed with its recovery.

Supercropping is basically the act of bending stems at a 90 degree angle so the plant grows horizontally instead of upwards. Doing this causes the plant to focus on repairing, which strengthens the branches for heavier bud production later on. Within a few days a branch that has become bent or twisted can be completely healed.

When the damage isn't too severe, i.e. the branch hasn't completely broken off, affected areas can heal even stronger than they were before. A thick knuckle-like scar develops which helps protect and support the branch. The horizontal growth also allows lower buds to receive more light.

How To Perform Supercropping:

  1. Wash your hands thoroughly.
  2. Select the tallest branches. The main stem is usually supercropped first to allow lower branches to catch up.
  3. Using your thumb and forefinger, gently rub or roll the area of the stem you plan to bend. This warms and softens the inside by exercising the outer fibres.
  4. At the soft point, bend/fold the stem or branch in the required direction and position.
  5. Provide the branch with support until the bent area has healed.
  6. After 2 - 3 days the branch will try to grow vertically again so you may need to tie it down.

Tip: It is not recommended to apply supercropping techniques after the first 2 or 3 weeks of flowering.


Cannabis Mainlining

Mainlining involves chopping off most of the lower growth of a plant so that only top buds remain. That includes all the lower foliage, branches, popcorn buds and other small flowers that do not form part of the canopy.

It is especially important to apply this technique gradually so plants do not become too stressed or have many open wounds at one time.

Normally, mainlining is used in conjunction with other training techniques such as topping. Growers will often top their plants, apply LST and let them recover before moving onto mainlining, but it can also be used on its own. Removing foliage in this way directs energy to the top of the plant, resulting in only primary buds. It makes harvesting extremely easy.

How To Perform Mainlining:

  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 all foliage and branching up till the 3rd node. Make sure you leave 1 or 2 sets of fan leaves.
  5. Tie down the two remaining branches of the 3rd node.
  6. Once the plant has recovered and new shoots grow, they can be topped. Topping should be done in a symmetrical fashion.
  7. Repeat until you have achieved the desired number of tops.

Tip: You don't necessarily have to throw away the shoots you cut off. Consider keeping any chopped stems as you may be able to save them for clones.


Cannabis Lollipopping

Although it is recommended that you avoid using too many stress techniques during flowering, sometimes a small amount can give your plants that extra push. It has been shown that some stress during flowering can actually cause plants to be more productive. Lollipopping does just that. Instead of wasting energy on leaves and flowers that will never fully develop anyway, it makes sense to remove them so the areas of the plant receiving light can work even more efficiently, and in the end produce bigger buds.

To properly lollipop your plants it is important that you do not remove too many popcorn buds. It is advised that no more than 50% of the growth is removed as this might stress your plant too much. Usually, this technique is applied during the 2nd or 3rd week of flowering. Applied too early on in veg and the popcorn buds might just grow back before flowering.

How To Perform Lollipopping:

  1. Sterilize clippers or sharp scissors.
  2. You can either remove growth gradually each day or at once.
  3. Working your way from bottom to top, remove 30% of lower leaves and popcorn buds. Do not remove more than 50%.
  4. Let your plant recover before stressing again (not recommended to stress further during flower).

Lollipopping on Cannabis Plant

Risks Associated With HST

There are of course some risks involved with HST. Be aware that training your plants too heavily during flowering (especially late flowering) may cause them stress from which they cannot recover properly. Most training should have been completed by the time the stretch period during the preflowering stage has ended. You want your plants to be at their best so they can focus on producing bud.

Make sure you take extra care when performing HST so you can avoid some annoying problems:

  • Hermaphrodites - Especially problematic if a cannabis plant becomes stressed too late into the flowering stage. Remember, some plants can handle stress better than others. Choose resilient strains that are not prone to mold and pests.
  • Mold - Manipulating your plant too heavily too often increases the risk of mold because wounds become the perfect breeding ground for bad bacteria, if things are not kept hygienic.
  • Broken Stems - It is possible that while applying stress techniques you can accidentally break off a whole branch or bud. Cannabis can handle a bit of rough and tough, but make sure you do not force or over-do it.


Stress techniques are definitely worth looking into if you already have some experience growing cannabis. It can be a difficult process to come to terms with, but once you have experimented with HST you'll understand your strains better and know what their limits are. If you keep at it, your harvests will be bigger and you'll be able to fit more weed into a smaller grow space. And what stoner doesn't like more bud?

High Stress Training MethodVegetationPre-Flowering

If you found this article useful, please consider leaving a comment. We'd love to hear about your high stressing training efforts and how they worked/did not work for your favourite strains.

External References

Apical dominance. Current Biology. - Barbier, Francois & Dun, Elizabeth & Beveridge, Christine. (2017)

Bonsai: their forms and planting techniques. - Mewar, Deepak & Joshi, Udit & Negi, Ruchin & Dhyani, Ajay. (2020). 

Evaluation of the Effect of Topping on Cannabidiol (CBD) Content in Two Industrial Hemp (Cannabis sativa L.) Cultivars. Bulletin of University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca. Horticulture. - Folina, Antigolena & Kakabouki, Ioanna & Tourkochoriti, Evangelia & Roussis, Ioannis & Pateroulakis, Harry & Bilalis, D.. (2020).

This article was updated October 2020.



Great :+1:


Great article, very informative. Always using as a resource during my grows.


Turns out, in my past grove I used the technique “Lollipopping” :point_up_2: :smiley:




Greate lecture!:+1:

Is it possible to mark a journal so you can find it again more easily?