Low Stress Training (LST) is a technique used by cultivators to gently manipulate a plant’s shape without causing significant damage. The purpose of LST is to increase the amount of light that reaches the lower sections of the plant, encouraging more uniform growth. Autoflowering plants transition from the vegetative phase to the flowering phase based on age, not the light cycle. This fixed, rapid life cycle makes precise timing and a gentle approach like LST crucial for maximizing potential yield.
Identifying the Optimal Window for Starting LST
The timing for initiating LST on autoflowers is critical because their vegetative phase is short and cannot be easily extended. The most effective window to begin training is when the plant has developed sufficient structure but the stem remains highly pliable. This stage typically aligns with the development of the third to fourth true node, usually around the second or third week after the seedling sprouts.
Starting the process too early risks damaging a fragile young plant that has not yet established a strong root system. The stem is thin and can easily snap under the slightest pressure, which would severely stunt the plant’s growth and recovery. Conversely, delaying LST until after the fourth node is well-developed allows the main stem to thicken and become rigid.
A late start makes bending more difficult and increases the risk of snapping the stem, negating the “low stress” advantage of the technique. Furthermore, autoflowers begin their pre-flower stretch quickly, often around week three to five, meaning the opportunity to shape the plant efficiently is brief. Initiating the bend during this sweet spot allows the plant to adjust its hormone flow and begin lateral growth before the flowering stage.
The Unique Physiological Need for Training Autoflowers
Autoflowering varieties possess a unique physiological constraint due to their ruderalis genetics, which dictates a fixed and short growth schedule. Unlike photoperiod plants, which remain in the vegetative state until the light cycle changes, autoflowers transition to flowering regardless of the grower’s input. This means the time available for a plant to recover from any setback is severely limited.
The plant’s natural tendency, known as apical dominance, is to grow a single, dominant central stem, or cola. This results in a Christmas tree shape where lower branches are shaded and produce smaller, less dense flowers. LST is used to break this dominance by pulling the main stem horizontal, which signals the plant to redistribute growth hormones evenly to all side branches.
This gentle manipulation encourages the side shoots to grow upward, creating a more uniform canopy where multiple bud sites receive equal light intensity. Because LST does not involve cutting or wounding the plant, the required recovery time is minimal, allowing the autoflower to continue its rapid growth without interruption. Maximizing lateral growth is paramount before the plant commits its energy entirely to the short flowering phase.
Step-by-Step Guide to Applying Low Stress Training
Applying LST involves gathering the necessary tools, such as soft, pliable plant ties or coated wire, and a way to anchor the ties, typically through holes drilled in the pot or weighted stakes. The main goal is to gently pull the dominant growing tip away from the vertical light source.
To make the first bend, stabilize the base of the main stem with one hand, which prevents the young plant from being pulled out of the growing medium. Use the other hand to gently bend the main stem over, aiming to angle it between 45 and 80 degrees from the vertical. The stem should be secured with a tie near the apical tip, anchoring it to the edge of the pot.
This initial bend redirects the growth hormones, causing the lower side branches to stretch upward toward the light source over the next few days. As the new shoots grow and compete for the highest point, they must also be tied down and spread out to maintain an even, flat canopy.
The grower should regularly check the main stem where the bend occurs, often called the “elbow,” to ensure the tie is not digging into the expanding stem tissue. Continuous adjustment of the ties, moving them further along the growing branches every few days, is necessary to keep all potential bud sites at a relatively equal height.
Practices to Avoid and Knowing When to Stop
Given the fixed, short life cycle of autoflowers, any practice that forces the plant to spend time recovering must be avoided. High Stress Training (HST) techniques, such as topping (removing the main growing tip) or FIMing, inflict wounds that cause a temporary but significant halt in growth. Since autoflowers cannot simply extend their vegetative period to compensate, this lost recovery time directly reduces the final harvest size.
The process of actively bending and securing new growth should cease when the plant enters the heavy flowering stretch. This phase typically begins around week four or five, marked by the rapid vertical growth and the emergence of distinct pistils. Continuing to aggressively bend branches at this point is risky because the stem tissue begins to harden and become less flexible, making it prone to snapping.
While new bending should stop, the existing ties should generally remain in place to maintain the desired horizontal structure throughout the flowering phase. The only adjustments made late in the cycle should be gentle repositioning to prevent branches from shading each other or to ensure good airflow. Once the vertical growth slows significantly and the plant is focused solely on flower production, the training period is officially complete.