Low Stress Training (LST) is a gentle horticultural method used to shape a plant’s growth structure to maximize efficiency and overall production. This technique manipulates the natural growth pattern to create a more desirable and productive form. LST is popular among growers seeking greater yields within limited spaces, such as indoor grow tents, because it achieves structural change without the severe trauma or cutting involved in other methods.
Defining Low Stress Training
Low Stress Training involves the physical manipulation of a plant’s stems and branches to encourage a flatter, more horizontal canopy. The “low stress” designation distinguishes it from methods requiring topping, cutting, or damaging plant tissue. LST works with the plant’s natural physiology, minimizing the recovery time required.
The core principle behind LST is disrupting apical dominance, the plant’s natural tendency to grow primarily from a single, central vertical stem. This dominance is maintained by the hormone auxin, concentrated at the main growing tip, which suppresses the growth of lower, lateral branches. By gently bending the main stem so it is no longer the highest point, the flow of auxin is redistributed. This shift encourages suppressed side branches to grow upward, transforming them into multiple primary growth sites.
Practical Application and Technique
Applying LST requires simple, non-abrasive materials and a consistent approach starting in the vegetative growth stage. Growers use soft plant ties, rubber-coated wire, or specialized clips to secure branches, avoiding thin string or wire that could cut the stem tissue. Timing is important; stems must be young and pliable enough to bend without snapping, often when the plant has developed three to five nodes.
The initial technique focuses on the main stem, which is slowly and gently bent until it is positioned nearly parallel to the ground or growing medium. The bend must be gradual, avoiding sharp angles that could crimp or break the stem. The main stem is then secured to an anchor point, such as the edge of the pot or a stake, to hold its new horizontal position.
As the plant grows, the side branches, released from apical dominance, will begin to grow upward toward the light. These new vertical shoots must also be trained down and outward to maintain a flat, even plane across the entire plant. This bending and securing process is continuous throughout the vegetative phase, requiring regular adjustment to ensure no branch is significantly taller than the others. The consistent manipulation forces the plant to spread out, filling the available space with an even layer of foliage and future flower sites.
Structural Outcomes of LST
The physical act of bending and securing the main stem initiates a significant physiological response within the plant. When the main stem is forced into a horizontal position, the concentration of the growth hormone auxin shifts from the primary tip to the new growth points. This redirection of auxin stimulates the dormant lateral buds along the main stem and side branches, causing them to develop into robust, vertical shoots.
This change in growth pattern creates a wide, flat canopy, moving away from the typical Christmas-tree shape seen in untrained plants. The most significant benefit of this structural change is the optimization of light exposure. Instead of having a single, dominant terminal bud that monopolizes the light, the even canopy ensures that light is distributed uniformly across all growth tips. This allows previously shaded bud sites on the lower parts of the plant to receive sufficient light energy for vigorous growth.
The result is a plant structure with numerous primary flowering sites, or colas, all developing at a consistent height and receiving equivalent energy. Furthermore, the open, spread-out structure of the canopy enhances air circulation around the developing flowers and foliage. Improved airflow helps manage humidity and reduces the risk of mold and pest infestations, contributing to the overall health and productivity of the plant.