Low-Stress Training (LST) is a gentle technique used to shape a plant’s structure without severe damage. This method involves carefully bending and securing stems and branches to encourage horizontal growth, creating a wide, flat canopy. The goal of LST is to ensure all potential bud sites receive optimal light exposure, promoting a uniform and productive harvest. Knowing when to cease the training is important for maximizing yield and plant health.
The Critical Transition Point
LST should be completed before the plant commits its energy to the reproductive phase, marking the shift from vegetative growth to flowering. For photoperiod plants, this transition is triggered by switching the light cycle to 12 hours of light and 12 hours of darkness. The period following this change is the “flowering stretch,” where the plant experiences a final burst of rapid vertical growth.
LST should generally be stopped just before this light flip or during the first one to two weeks of the 12/12 cycle. Continuing manipulation after this point is counterproductive, as the plant focuses on flower production, not structural development. This timing allows the plant to set its final structure and dedicate resources to the vertical elongation of the colas. Once the framework is established, the plant needs to be left alone to fill out the canopy.
Physical Indicators to End LST
Growers should look for physical signs confirming the plant has entered the flowering stage, signaling that LST must stop. The earliest visual cue is the appearance of pre-flowers—small, wispy hairs that emerge at the nodes where branches meet the main stem.
Another indicator is the rapid hardening and stiffening of the main stems and branches. During the vegetative stage, stems are flexible, but as the plant transitions to flowering, the cell walls thicken, causing them to become rigid and woody. This loss of flexibility means that further bending will likely cause permanent damage.
The most dramatic sign is the onset of the flowering stretch, characterized by a sudden increase in the distance between the nodes. Once this vertical surge begins, the plant’s structure is largely fixed, and continuing LST will interfere with the final upward growth.
Management After Training Ceases
Once Low-Stress Training stops, the focus shifts to supporting the existing plant structure and optimizing light for flower development. Any ties or wires that are digging into the thickening stems should be promptly removed to prevent girdling, which restricts the flow of water and nutrients. The branches will have set their position due to the hardening of the stem tissue.
Because the plant is about to enter a period of vertical growth, introducing structural support becomes necessary to manage the stretch and prepare for the weight of the developing flowers. This often involves setting up a trellis net or using stakes to secure the main colas as they elongate. This ensures the uniform canopy created by LST is maintained without the risk of heavy branches collapsing later in the flowering stage.
The plant’s nutrient requirements also change, moving away from high-nitrogen formulas that promote vegetative growth. Growers should transition to a nutrient regimen higher in phosphorus and potassium to support flower and fruit production. Finally, a strategic, light defoliation can be performed to remove fan leaves that are blocking light from lower bud sites, ensuring all parts of the fixed canopy can access the light necessary for dense flower formation.