High Stress Training (HST) vs Low Stress Training (LST)

Last updated: 13 February 2020

low stress training

Training your cannabis plants is important because it can dramatically increase the yield and quality of your crop. Low stress training (LST) and high stress training (HST) techniques can help achieve this through minimal monetary investment and a little extra time. LST involves bending your plants into a desired shape, and HST methods are based on intentionally wounding the cannabis plant.

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The Science Behind Training Cannabis

The growth of a cannabis plant is dictated by auxin, a plant hormone essential for the development of the plant’s body structure. Plants typically have one or a few main buds at the top of the plant, with smaller buds on the branches below. Auxin is highly concentrated at the top of cannabis plants, hence the one main cola that grows on untrained plants. The training techniques in this article can help reduce top heavy growth and instead focus on an even canopy of multiple colas, as well as function to maintain plants at a discreet height by simply bending the plants and encouraging horizontal growth.

Low Stress Training: A Breakdown

lst cannabis

Low stress training (or LST) is an artistic growing technique comparable to bonsai. The stems and branches are gently manipulated and tied into place, creating a level canopy and dramatically changing the shape of the cannabis plant without causing it any stress. By doing so, multiple bud sites can develop due to their exposure to more light and, thus, the opportunity to develop more auxin. As a result, bud sites on lower branches will develop in size and quantity. LST is also useful for plants that are getting too tall for your setup, or need to be reduced in height to maintain discretion. Low stress training is ideal for small spaces and thrifty growers, also appealing to those who work with auto-flowering strains, as this method places essentially no stress on the cannabis plants.

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Advantages of Low Stress Training

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low stress training results

At its core, low stress training gives the grower the opportunity to achieve a much greater yield from the cannabis crop in comparison to allowing the plant to grow naturally into a conical shape. Typically, a cannabis plant has one main cola at the top of the plant, otherwise known as apical dominance. Through the utilization of LST, it is possible to induce multiple viable colas by creating a spread-out canopy that all grows at the same height.

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LST has multiple benefits, mostly due to better light distribution. By bending the branches in a way that encourages horizontal growth, the lower branches have the opportunity to absorb more light. The grower can achieve a bigger yield without having to adjust the setup and grow lights; because the colas are all at the same height, the buds will be ready to harvest at the same time. This complete control over the shape, height, and size of the plant requires consistent attention, in that LST is an ongoing process throughout the vegetative state of the cannabis plant, but the grower will be handsomely rewarded with a healthy, hefty crop.

How to LST Your Cannabis Plant

how to low stress train

So, you’re ready to start low stress training? This method requires few materials and is a low-cost way to increase the yield of your crop. Here’s what you will need:

  • Plant wire or soft plant ties (string or wire not coated in rubber risk damaging the plant)
  • Small wooden stakes
  • Small hand drill
  • Duct tape
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Start by drilling small holes around the perimeter of the rim of your growing container. This way you can secure your tied branches to the container. Small wooden or bamboo stakes are ideal for extra support. One should gently pull the branches away from the plant in a star-shaped pattern, helping to expose them to more light and reducing the height of the cannabis plant. Consider the flexibility of the branches; it is optimal to tie them off from the ends of the branches, where they are more pliable and less likely to break. However, accidents happen! If a branch snaps during this process, that’s where the duct tape comes in. Simply bandage up the broken area and the plant is very likely to repair itself within the next several days.

low stress training tutorial

bending weed plants

Although many growers top their plants before beginning LST, it isn’t strictly necessary because the main stalk can also be trained to grow horizontally along with the lower branches. Topping is useful for breaking apical dominance, but it is encouraged to skip the topping process with auto-flowering strains, since their vegetative periods are typically not long enough to recover from topping if anything goes wrong. 

When is it optimal to start LST?

When to start low stress training

The easy answer: as soon as possible! LST can be started once the cannabis plant has 4-6 good nodes and has established itself in the vegetative state. Anytime during the vegetative state is an appropriate time to start LST, although the earlier the better. Proper LST does not cause the plant any damage and the crop should recover quickly with help from the optimal light exposure. It is not recommended to begin LST in the flowering stage, because by this point the stalks and branches are likely too rigid to respond to training and are at risk for breakage when the plant structure is compromised.

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Step-by-Step low stress training tutorial

Plant bending techniques

Step 1: Top or bend your plant when it has 4-6 nodes on the main stem

It is common practice to top your cannabis plant (a process explained later) at the beginning of the LST technique, but it is not strictly necessary. Combining LST with a HST method such as topping is a good way to encourage horizontal growth. However, it is possible to LST without topping. Instead, simply bend the main stem down to the same level as the rest of the plant. This step, whether you bend or top the plant, is crucial for breaking apical dominance. If you choose to bend the main stem, secure it in place using soft plant ties and fasten them to the pre-drilled holes around the rim of your container. Be careful to bend the stem at its most flexible point to avoid breakage.

Step 2: Bend the other tallest stems

Next, bend the other tallest stems to create an even canopy and begin encouraging horizontal growth. Once again, be gentle with the branches and work only with those that feel flexible enough to be suitably tied down without breaking. The main idea here is to maintain a level canopy so that all stems are equidistant from the light source. Secure the stems to the container using plant ties. The earlier you train your cannabis plant, the softer and more pliable the stems will be.

Step 3: Maintain a level canopy

Repeat step 2 throughout the vegetative stage once the canopy is uniform and the branches are starting to reach up again. LST is an ongoing process and requires diligent upkeep, and you will see how after a few days the stems start growing upward again. Continue bending and tying shoots horizontally and away from the main stem in a star shape. Pay close attention to your plant to ensure a flat canopy with even light distribution.

Step 4: Watch your cannabis plant flourish in the flowering stage!

Check out all those extra colas growing big and strong! Once your plant enters the flowering stage, all the buds should grow incredibly quickly and at the same pace. At this time, it is also advisable to prune the lowest branches on the cannabis plant, as they will no longer have the chance to get as much light as those on top. Pruning at this stage can boost production at the top of the plant, since the plant will no longer be wasting energy on the lowest branches which have no effect on the ultimate yield of your plant.

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Okay, But What About High Stress Training?

high stress training

High stress training (otherwise referred to as HST) is a process that involves breaking or removing parts of the cannabis plant in order to optimize the growth of the crop. When done correctly, the yield of your crop can be exponentially increased. This type of training is most common in large outdoor grow operations, and should only be applied to plants that are in the vegetative stage. Once a cannabis plant is flowering, any exposure to extreme stress may be too much to withstand and the plant is less likely to heal itself. The same goes for plants that are weak and sick; HST should be performed only on healthy cannabis plants.

HST: Not just one method to enhance your crop!

By intentionally wounding the plant, the grower can stimulate optimal growth in the cannabis plant. HST techniques involving cutting top growth and bending branches are utilized during the vegetative stage to increase the potency and production of buds during the flowering stage. There are several training methods including topping, FIM, and super cropping, which are detailed below.


topping marijuana

Topping is a very straight-forward, uncomplicated high stress training technique. The only tool you need is your own fingernails! The objective is to clip the top growth of the plant, prompting the cannabis plant to grow two new stems where the top of the plant previously was. This method sends a shock through the entire plant when it is topped, also boosting growth in the lower branches. Topping is an HST approach that may be repeated throughout the plant’s vegetative state, in order to induce a plentiful crop of healthy, hefty buds.

FIM (“Fuck I missed”)


Another HST method, a more complicated version of topping, is FIM, or “Fuck I missed” (humorously implying that topping went wrong). FIM involves the removal of a very specific amount of the top growth of the cannabis plant. When topping, the grower can achieve two off-shooting branches from the clipped portion of the plant; when FIM is executed correctly, the plant will produce four new branches instead of two. An important distinction between the two methods is exactly where the plant is cut. When topping, the entire new growth is removed from the top of the main stem, but with FIM, only the upper half of this new growth is trimmed.

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Since this method is more complex and stressful than topping, it does take considerably more time and requires a tool rather than only the fingernails. Recommended would be a pair of pruning scissors or a razor blade, properly disinfected to avoid introducing infection to the cut stalks. The cannabis plant is put at greater risk of illness or infection because the intentional wounding of the stalk is not done with a clean cut at the bottom of the new top growth. When done correctly, this method produces considerably more stems and, later on in the flowering process, plenty of buds.

Super cropping

Super cropping

Super cropping is a high stress training technique that utilizes stem mutilation to decrease the height of the plant and stimulate growth. The goal of super cropping is to break down the inner fibers of the branch so that the stalk becomes pliable and can be trained into another position, all without harming the outside of the stem in the process. Start by grabbing the branch where you would like to bend it, and roll it between your forefinger and thumb. After about ten seconds of rolling and wiggling, you’ll feel the inside of the branch loosen up and become more flexible. Once it is soft enough to bend without breaking, secure the branch to stay bent, ideally with plant twist ties (but regular zip ties should also be okay). If the outside of the stalk does happen to snap or tear in the process, bandage up the exposed area with some duct tape and remove after a week or so. Chances are, your cannabis plant will heal herself right up!

Although super cropping is an HST method, it mirrors the techniques behind LST in a more aggressive manner. As opposed to tying down the the branches of the plant, the grower bends the branches until the inner fibers break down and become flexible enough to fold over. This technique is best done while the cannabis plant is still in its vegetative state, or only very early in the flowering stage, because it is not recommended to stress your cannabis plants during flowering. Super cropping is a great method to give the lower branches of your cannabis plant the opportunity for more light exposure and to develop at a similar rate to the top stalk.

How HST can increase your success

High stress training cannabis

The benefits of high stress training are similar to those of low stress training, in that when done correctly, HST can result in shorter plants with many more buds than an untrained plant. It is also understood that high stress training can increase the levels of THC and CBD in cannabis plants, because cannabinoids act as the cannabis plant’s defense system in the wild. Topping and cutting the plant puts it under stress, and it follows that the crop would increase its protection when under attack.

The purpose of these cannabis training techniques is to modify the physical and chemical balances in the plants by reducing the naturally upward focused growth of cannabis plants and instead encouraging the plant to grow a level canopy. Especially in an indoor garden, the light source should only be as close as is ideal for the top cola. When all colas are at a similar level, the lower branches have the opportunity to absorb more light and grow larger at the same time as the main top cola. When done correctly, LST and HST methods can drastically increase the yield and potency of the crop. Plant bending techniques are very useful for growers with limited grow space, value discretion and thus need to maintain a specific height for their plants, or simply those who wish to maximize the potential of their grow.

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Meal..I always use HST and LST technology.. the Hulk trunks speak for themselves..after a month of growth, little trees were estimated to be 2 years old xD measured 37 mm in diameter ...woody...
i life in tropical country and It is very bright with the sun almost 11 hour, I have bought the Indica. will I have any problem when it grow? (to much light) is it enough to put in my room which have the light from the sun out side or just bring it out to get direct sun? please advise
Hello Bestben,The light itself does not damage the plant, but light also brings temperature. If it is too hot, the plant may suffer from dehydration or even sunburn, you will need to keep the temperature in mind and perhaps cover the plants with a net to avoid sunburn. Overextension light is no good, Sativa strains are more tolerable to it rather than Indice you've planted, the net should resolve the problem, perhaps additional watering will be needed as well. Do you grow in pots? If so, you can move the plants to the shade to let them cool down a bit
I've done a lot of tests comparing fimming to topping and everyone explains it incorrectly. The real difference between fimming and topping is that fimming doesn't stop the main stem from continuing to grow. It slows it down letting the plant focus on lower nodes while repairing where you fimmed it., but also forces the plant to spend energy growing back parts of the fan leaves you chopped so it's not a strategy I'd impliment in any scenario other than when one of your plants is getting too tall versus the others, but you don't want to top it yet.
and just to add, it doesn't give you 4 more colas other than the fact that the new node above it will grow back. That's a myth. Topping the plant will put even more energy into both the node you cut it above and the one below it than fimming will. If you want more colas, top those branches again or skip a node on each branch and then top them to do more of a manifold if you want to do it quicker.
Hello Stoner, The FIM allows to reroute the growth process, as you have mentioned to the other nodes. Which gives an opportunity for experimentation in this area to find the best way to FIM your plant. Thank you for sharing your experience with us.
What’s the most effective technique to control upward growth amongst these? My plants are getting too big and I wanted to save space for some new ones
Hello MC, most effective, but not easiest one method to control height of your plant is stress training
Turn the light off. jkI don't think you can really control growth... it’s in the plant’s DNA
Well that isn’t truth at all. I am into a particular style of gardening called “bonsai”. Which in essence is all about controlling plant growth to maintain a small canopy. This also can be done with cannabis and just about any type of plant.
Topping will slow the upward growth, but they will be bushy.
you know, i never know what i should do when i go into flower. do you remove the ties before you flip or do you leave them tied for the entire life of the plant? i've always left them but it's bugging me that i don't know for sure
Hello,Depends on how do you tie them, long ago so they will keep their shape or not. Also, sometimes you can even tie them to spread the flowers when they already in a flowering stage, usually compelled with hard stress training to make plant produce more THC about 2-3 days before harvest
It's all about personal preference, IMO. I like to leave mine tied...Truly like a SCROG, without the screen, but i know a lot of others like to untie theirs before or after the stretch. If you untie then the mainstem will straighten up and become the dominate top again, i do not want that as I want my canopy to be as even as I can get it.
I've got to say, a plant that has no LST or pruning is one heck of a lot easier to manicure the buds off of. There are so much less of them, but the same overall weight if enough room is allowed for the unmodified plant to grow in, like it would be if it were grown outside or in a room with a very tall ceiling. I used massive LST on my last grow and the manicuring was a nightmare. I didn't know if my arms would last long enough to finish!
nice to share the fact,,,, how is your yield get with that?
For LST I personally use those pipe cleaner type thingies. I start at about 3 weeks.
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