Low-Stress Training (LST) is a horticultural technique used to physically manipulate a plant’s growth structure to maximize light exposure and manage the canopy size. This method is particularly effective for indoor cultivation where space is limited, shifting the plant’s growth from a tall, narrow shape to a shorter, wider one. By guiding the plant’s development, growers ensure that lower branches receive sufficient light to develop into productive growth sites. LST increases a plant’s yield potential without causing severe trauma.
Defining Low-Stress Training
LST is defined by its gentle approach, utilizing physical manipulation to redirect plant growth without cutting or causing significant injury. This technique directly counters apical dominance, a biological phenomenon where the main, central stem grows fastest and suppresses the growth of lower, lateral branches. This dominance is regulated by the plant hormone auxin, which is produced in the terminal bud at the plant’s apex.
When the main stem is bent over, the apical bud is no longer the highest point, disrupting the flow and concentration of auxin. This hormonal redistribution signals the previously suppressed lower branches to grow vigorously toward the light source. LST converts these side shoots into multiple primary growth sites, or “colas,” transforming the plant’s shape from a single-stemmed structure into a broader, bushier form. This manipulation redirects the plant’s energy to form a uniform, level canopy.
Essential Materials and Timing
LST requires materials that are soft and non-abrasive to prevent stem damage. These tools secure branches without cutting into the stem as it expands. Traditional string or bare wire should be avoided, as these materials can constrict and girdle the stem over time.
Materials
- Soft plant ties
- Coated garden wire
- Specialized LST clips
- Anchor points, such as holes drilled around the rim of the container or components of the grow tent frame
The optimal time to begin LST is during the early vegetative stage of the plant’s life cycle. This typically occurs when the plant has developed between four and six nodes, or sets of leaves. Stems are young and pliable at this point, making them easy to bend without breaking. Training should continue throughout the vegetative phase and stop just before the plant enters the flowering stage, as hardening stems make further bending risky.
Step-by-Step Implementation
The LST process begins by gently bending the main stem horizontally until the tip is level with or slightly below the surrounding branches. This horizontal positioning is secured by looping a soft plant tie around the stem, ensuring it is not tied too tightly, and then anchoring the other end to the side of the pot or a fixture. The goal is to encourage the plant to grow outward rather than upward.
As the plant grows, new shoots will quickly turn and grow vertically toward the light (phototropism). These newly upright branches must also be bent and secured outward and downward to maintain the level canopy. This ongoing maintenance involves adjusting existing ties and adding new ones to continuously spread the canopy, aiming for an even, table-like surface. Regular monitoring is necessary to ensure fan leaves are not shading potential growth sites, sometimes requiring minor tucking or repositioning to maximize light penetration. Patience and gradual adjustment are necessary, as forceful bending can easily snap the branches.
Advantages for Home Growers
LST offers advantages, particularly for home growers operating in small indoor spaces. By forcing the plant to grow wide instead of tall, the technique allows growers to manage the plant’s vertical height, preventing it from outgrowing the grow tent or light fixture. This efficient use of space is a key benefit for those dealing with height constraints.
The resulting level canopy ensures that all potential bud sites receive a uniform distribution of light energy. While only the top layer receives maximum light in an untrained plant, LST exposes a greater surface area to photons, maximizing photosynthetic efficiency. This uniform light exposure and hormonal distribution across the numerous “colas” translates directly to increased yield potential. The improved airflow around the spread-out foliage also helps reduce the risk of mold and pest infestations, contributing to healthier plant development.