Cannabis training techniques: LST vs HST… Which one is better?

Growing marijuana is not just about planting and harvesting. Growers are constantly looking for ways to optimise plant growth and maximise yield. Two popular techniques in this field are Low Stress Training (LST) and High Stress Training (or HST). But which of these is the most suitable? In this post, we’ll analyse both methods to help you make the best decision.

No matter the size of your grow: Training your cannabis plants is a reliable ritual that will greatly increase their quality and yielding capacity. Genetic studies show that cannabis plants go into survival mode in adverse conditions, leading to several desirable benefits if addressed correctly. As a result, growers have learned to offer a controlled stress environment to stimulate and manage the productivity of their plants.

What effects does training produce?

The reason why many plants grow toward the sun in the shape of a Christmas tree is because they produce high levels of growth hormones (called auxins) closer to the top of the plant, whilst their side branches are inhibited from producing them. This phenomenon is called apical dominance and is the reason why cannabis plants grow a main tall cola in the centre and many smaller colas on the sides.

Training methods are used to reduce concentrated upward development and encourage the growth of a levelled canopy. This way, instead of diverting most of their energy towards their central cola, some plants spread it more evenly to produce more flowering sites and high calibre buds.

This allows plants to grow stronger, to have more access to light and better ventilation, and to produce higher yields. And, if you grow indoors in a reduced area, to also keep your plants from outgrowing the available space.

What types of training are there?

There isn’t a training technique that’s more popular than others. The two main training methods are the following:

Low Stress Training (LST)

LST consists of carefully bending the stems and tying them firmly to mould the shape of the plant in a more horizontal plane. A lot of care is required to ensure that none of the stems break, so it is best to do this when the plants are young and flexible.

When the plants are encouraged to grow a horizontal canopy, light can reach many more leaves so the plants have more energy to grow. This also means that, if you grow indoors, you can dim the grow lights to bring them closer to the canopy, meaning you can use lower-powered bulbs, which in turn saves energy and money.

Some of the most common low stress training techniques include:

• Bending of the branches: It consists in gently bending the branches and tying them with wires or string to redirect their growth horizontally.
• Spiral LST: This technique involves winding the main stem and branches around a spiral structure, such as a ring or mesh.
• Defoliation consists of selectively eliminating some large leaves to improve light penetration and air flow to the lower parts, which promotes the overall health of the plant.
• The SOG (Sea of Green) method involves growing many small plants together, forcing them to flower early to create a uniform “sea of green,” which maximises the use of the space and allows for a quick harvest.
• The SCROG (Screen of Green) method implies the use of a mesh to train the plants, extending their horizontal branches along the screen to ensure that all branches receive an even amount of light.

High Stress Training (HST)

High stress training is a somewhat more intensive technique which involves pruning, cutting, or even damaging the stems of the plants rather than gently bending them. The general idea is that plants have built-in hazard responses: when they feel threatened or injured, they produce trichomes and cannabinoid compounds that improve their quality and strength. HST can be more complicated than LST because, if plants aren’t in the best health, injuries can have the opposite effect.

Common high stress training techniques include:

• Topping: It consists of cutting the tip of the apical stem to stimulate the growth of multiple lateral branches, which can increase the number of flowering sites.
• Fimming: This is a variation of topping that involves cutting approximately 75% of the tip, encouraging the growth of multiple branches in a less precise way.
• Super cropping involves bending and slightly damaging the branches without breaking them, which induces the plant to strengthen those areas and increase its resistance to the weight of the buds.
• Mainlining is a technique that combines topping and low stress training to create a symmetrical structure with multiple main colas, thereby optimising the distribution of energy and resources in the plant.
• And lastly, Lollipopping consists of removing the lower branches and leaves that don’t receive enough light, focusing the plant’s energy on the higher and more productive shoots.

LST or HST? Which one to choose?

The choice between LST and HST depends on several factors which include your level of experience, the available space, and your specific growing objectives. For beginners, LST can be a safer and more manageable option, as it offers good control without the risks associated with high stress techniques. On the other hand, more experienced growers who are willing to invest time and care in the recovery of their plants can greatly benefit from implementing HST.

Combining LST with HST

These two training methods can also be combined, which can have both advantages and disadvantages. Benefits include yield maximisation, as HST can increase the number of flowering shoots, whilst LST optimises exposure to light and airflow.

This combination also allows you to precisely shape and direct plant growth to obtain a balanced and well-distributed structure. And the resilience of the plants is also improved since controlled stress can strengthen them and make them more robust in the face of possible problems.

However, mixing both techniques also requires a higher level of knowledge and experience. This process demands more attention, as regular and careful interventions must be made to ensure a proper recovery from the induced stress.

Finally, there’s an inherent risk associated to overtraining your plants, which can result in a major failure rather than an improvement. But high risk equals high reward. Therefore, if you keep track of your methods, find the perfect technique by trial and error, and evaluate growth factors, you can be sure that your next grow will lead to one of your biggest crops ever.