Cannabis high-stress training how-to tutorial

08/04/2022

Cannabis plants can be grown naturally without any training techniques. For the more experienced growers seeking to improve yields, there are the options of low stress and high stress training. Low stress training includes techniques such as SCROG, tying down branches etc.

High stress training (‘HST’) involves some radical deliberate damage to your cannabis plant in order to achieve some important benefits, including heavier yields. However, HST also carries certain risks. You will need to time your HST carefully to ensure optimum results and follow some rules to avoid issues. Less experienced growers will probably prefer to gain experience with LST before attempting HST.

What is high-stress training for cannabis?

Desfrán grown in a half-pipe SCROG with bending and super cropping.

High stress training for cannabis should only be conducted on strong, healthy plants. Attempting HST on a weak or diseased plant only causes unwanted additional stress. HST in the form of ‘super cropping’ involves taking a pliable branch (or the main stem) and gently crushing it between thumb and finger, between the internodes.

This squashes the cell walls, temporarily weakening the branch allowing it to be bent over so it is positioned in a horizontal rather than a vertical position. Using some twine/cord, the branch is firmly secured in its new horizontal position to prevent it reverting to vertical growth.

This is called super cropping and it produces an increase in levels of hormones associated with repair and growth. The plant will recover over a few days creating a tough, woody ‘knuckle’ at the point of HST. Once completely repaired, the plant is stronger than before.

High stress training – topping and fimming

Many growers also regard the topping and fimming techniques as HST. Topping is simply the removal of the growing tip of the plant. Without the growing tip (or ‘apex’), the plant adopts a shorter/bushier nature with extra side branching. Topping can be performed on both autoflower and feminised strains, but it does cost the plant several days of growth time while it recovers.

Fimming is a slightly more difficult/imprecise technique to perfect. The principle is similar to topping. However topping tends to replace the growing tip with two side branches whereas the FIM technique hopes to replace the growing apex with 3, 4 or more branches.

Master Kush grown organically with some bending/supercropping.

Pros and Cons of high-stress training (HST)

Cannabis high stress training isn’t universally recommended. It suits the more experienced grower who has the knowledge and practical skill to handle the situation. Not all cannabis plants will respond particularly well to it. So take your time, do your research carefully and if in any doubt gain experience with low stress training first.

Pros of high stress cannabis training

HST is a good solution for any grower with limited vertical grow space and a plant that is outgrowing the available headroom. By applying super cropping to the tallest branches, the grower can instantly accommodate the plant. Outdoor growers also use HST to tame vertical growth if security/visibility is a concern.

Growth, plant structure and vigour are all improved.

Yield will be improved. The release of growth hormone during repair aids future growth and subsequent yields.

HST with super cropping takes a branch that was growing vertically and moves it into a horizontal growth position. Skilled growers can use this to place numerous future bud points into the optical sweet spot of their grow light. This allows more of the buds to bathe under optimised PPFD light levels, optimising future yields. This is one of the ways that many super cropping converts are able to boost yields.

HST with topping is a great way to take a take stretchy strain (which may outgrow the available vertical space) and alter the growth structure to a more squat, bushy structure.

The Ultimate grown in a SCROG with some cropping/supercropping.

Cons of high stress cannabis training

Get the technique wrong and you could damage your plant and reduce future yield.

HST will take up to 5 days for the plant to repair the damage with a wood-like knuckle, it will cost time while the plant recovers.

Less knowledgeable growers can run into issues especially if they lack practical experience working with plants and applying training techniques. This can reduce final yields rather than increase them. Knowing how much stress a plant can take often comes with practical experience.

Allow insufficient time for the super-cropping to repair and you create extra stress for your plant which may reduce future yield or risk an infection in open plant wounds (tape is recommended if the stem splits during supercropping).

When to start high-stress training?

Experienced growers tend to apply LST or HST only during vegetative plant growth. When growing photoperiod feminised cannabis seeds that means training your plants before flipping them into 12/12 bloom conditions. By avoiding the additional stress of applying HST in bloom, you maximise your chances of success.

If growing autoflower seeds you should aim to apply training techniques while the plant is still in vegetative growth mode. Often this is in the first 4-5 weeks following autoflower seed germination.

High-stress training weed plants step-by-step

When supercropping, apply gentle pressure until you can just feel the firm plant tissues crush.

HST, for the skilled grower, shouldn’t seem daunting. The following step-by-step guide may help you plan your HST treatment more effectively.

Identify the branches where you want to apply HST. Ensure that you have all the materials (string etc) ready so you can tie-down the branches as soon as they are super cropped. If topping/fimming use a clean, sharp razor blade or similar.
Ensure your hands are clean and sterile. In the event of a super cropped branch breaking you don’t want to infect it with dirt. Instead, apply a small section of tape to cover the wound which should heal within 3-5 days.
When supercropping, apply gentle pressure until you can just feel the firm plant tissues crush.
Allow the branch/stem to slowly take on a horizontal position then tie it into place with some garden cord. If using airpots, you can thread garden cord through the air holes to tie the branches down.
The skilled grower will ensure that as many bud points as possible are kept in the optical sweet-spot of their grow light. This maximises future yields.
More than one branch can be super cropped, use HST as required to maximise and optimise yields from your grow space.
If applying the topping technique note that you can use the removed growth tip from a photoperiod feminised strain as a cutting to grow a new plant.

A note on mainlining cannabis

A high stress training technique known as mainlining is used by some cannabis growers.

An HST technique known as mainlining is used by some cannabis growers. Although it can be regarded as a somewhat fiddly and labor intensive technique it can allow growers to prune their plant into the classic mainline shape to maximise yields.

In general, the majority of those applying HST techniques do so with the super cropping principle or topping/FIM rather than the mainlining approach.

High-stress training autoflowers tips and tricks

Autoflowers can be grown with high stress training in the same way that photoperiod feminised strains are. However, one limitation with autoflowers is that they tend to have relatively short periods of vegetative growth, often around a month or so. That gives only limited time for the grower to apply HST techniques.

Problems may occur if the grower realises the autoflower main stem is stretching too close to the top of his tent after early bloom has started. So although it really is not recommended to apply HST in early bloom, there may be moments when HST in early bloom is the only way to allow the plant to fit in the available vertical space.

Less experienced auto growers should refrain from HST in bloom. Experienced growers who see HST as the only plant-saving option may prefer to roll the dice and apply HST during early autoflower bloom, accepting that there are no guarantees of success.

1. Ensure you have clean hands when applying the super cropping techniques to prevent accidental infections if the plant stem breaks open. Use clean/sterile tools when defoliating leaves or pruning/topping/fimming your plants.

2. Always allow your plants ample time to recover when performing H.S.T. You will note how the super-cropping wound recovers with a thick wood-like knuckle which needs time to form.

3. Avoid applying high stress training techniques once your plants are in bloom unless you are highly experienced. The combination of hormonal changes at the same time as high stress levels may cause hermaphrodite plants to occur.

4. Training cannabis plants really does takes time, experience and patience. Gaining practical experience with low stress training is recommended before considering HST.

5. Mainlining is an option for autoflower growers. It’s recommended to do some background reading/research first since it requires a lot of manual work to create the mainlined shape/structure.

In general, the majority of those applying HST techniques do so with the super cropping principle or topping/FIM rather than the mainlining approach.

Topping/fimming autoflowers: is this HST method recommended?

Many experienced growers routinely top their autoflowers feeling that the additional yield outweighs the time lost while the auto is recovering from the topping. However it is worth adding that not all auto growers are convinced that topping them is a good idea. Find out what works for your grow situation, and if in doubt you can always gain experience cultivating autos in the natural way before assessing HST effectiveness.

Don’t be afraid of HST with cannabis cultivation

Think Fast grown outdoors using some fimming.

The idea of deliberately crushing the supportive cell wall tissues to your prized cannabis plants or cutting off the growing tip may take some getting used to. It may feel inherently ‘wrong’ and indeed some growers don’t like using super cropping or any other HST technique.

If that sounds like you then you may find it useful to practice super cropping on your existing plants as you cut them down for harvest. If you make a mistake it won’t matter! Just take a few of the smaller branches on your harvest-ready plant and practise applying pressure until the branch crushes. The process feels a little different on old vs young branches but the process/principle is the same.

Once you are ready to try HST on a ‘real’ crop it’s important to focus on securely tying down the super cropped branch. If not, it will eagerly revert to vertical growth with a few days.

That aside, HST is relatively straightforward and nothing to feel intimidated by. Many growers love to apply HST to their tallest branches/stems, this allows more of the subsequent bud points to receive optimised light levels. Seeing the extra bud production come from your plant is a great reward for the work and risk!