Low-Stress Training (LST) is a horticulture technique used to gently manipulate the shape of a cannabis plant without causing significant damage. This method involves bending and securing the main stem and branches to grow horizontally instead of vertically. The goal of LST is to break the plant’s natural apical dominance, which causes the central stalk to grow tallest, forming a single main cola. By forcing the top of the plant to an angle, LST encourages lower branches to grow upward, creating a uniform canopy to maximize light absorption across multiple bud sites. Autoflowering cannabis plants flower automatically based on age rather than changes in the light cycle, making their growth schedule fixed.
Why LST is Ideal for Autoflowers
Autoflowering varieties have a genetically determined, compressed life cycle, with a vegetative phase that typically lasts only three to four weeks before flowering begins. This short window of growth makes them sensitive to techniques that require a long recovery time. High-Stress Training (HST) methods, such as topping or fimming, involve cutting the plant, forcing it to divert energy into healing the wound.
Applying HST to an autoflower can result in stunted growth because the plant may not fully recover before its internal clock triggers the flowering phase. Since the plant’s size is determined during this brief vegetative period, any significant delay reduces the final harvest size. LST involves only gentle physical manipulation, allowing the plant to maintain uninterrupted growth momentum. This gentle approach permits the grower to shape the canopy and expose more flowering sites without sacrificing days to stress recovery.
Essential Preparation and Timing
Successful LST requires non-abrasive materials that will not cut into the plant’s tissues. Growers should use soft-coated garden wire, flexible rubber ties, or padded pipe cleaners, securing them to anchor points on the container or a surrounding frame. Using materials that are too thin or sharp can cause girdling, where the tie cuts into the stem as it thickens, hindering nutrient and water flow.
Training should be performed when the plant is sturdy but still flexible, typically around the third or fourth week of growth. At this stage, the plant will have developed at least three to five distinct nodes, meaning the stem is mature enough to withstand gentle pressure. Starting too early risks snapping the fragile seedling stem, while starting too late means the stem has hardened and is less pliable. It is important to cease any significant bending or tying once the plant enters the pre-flowering phase, which occurs around Week 5 or 6 for many autoflowers. Continuing aggressive training after this point can disrupt the hormonal shift toward bud development, potentially stunting the final size.
Step-by-Step Execution and Ongoing Maintenance
The initial step in LST is to carefully bend the main stem sideways, aiming for an approximate 90-degree angle to the soil surface. This action breaks the plant’s natural vertical growth pattern, signaling to the lower branches that they can now compete for light. The apex of the bent stem should be secured using a soft tie anchored to the edge of the pot or growing medium. This position encourages the growth hormone auxin to redistribute, stimulating the lateral side branches to grow upward toward the light source.
Once the main stem is secured horizontally, the side branches exposed to direct light will begin to grow vertically. Ongoing maintenance involves a series of “secondary bends” every few days to maintain a flat, even canopy. As new side branches grow taller, they must also be gently bent and tied down to the same height as the main stem. This continuous manipulation ensures that all potential bud sites receive uniform light exposure, maximizing the number of productive colas.
Canopy management also includes minimal, selective removal of large fan leaves that cast heavy shadows on developing bud sites below. While defoliation improves light penetration and airflow, it must be done sparingly in autoflowers to prevent stress that could slow growth. The focus should be on creating a consistently level plane of growth by regularly checking and adjusting the ties.