Plant training techniques are widely used in horticulture to manage plant growth and optimize the use of light and space. The Screen of Green, commonly known as SCROG, is an advanced method designed to maximize light exposure across the entire upper surface of a plant. This technique transforms the plant’s natural vertical growth into a dense, horizontal canopy, leading to a more uniform and productive harvest. SCROG requires careful planning and continuous maintenance throughout the plant’s life cycle, providing a high-efficiency solution for growers with limited vertical space.
Defining the Screen of Green Technique
The SCROG technique involves placing a physical mesh screen or netting above the plants to control their shape and direction of growth. Instead of allowing the plant to develop one main central stalk, the screen forces the branches to spread out laterally. This manipulation creates a flat, even plane of foliage, resembling a “green screen” when viewed from above. The primary goal is to ensure every potential flower site receives a similar, high level of light intensity.
By training the plant to grow horizontally, the grower can maximize the usable area under the light source, especially in indoor environments where light intensity drops off sharply with distance. The screen acts as both a training guide and a support structure for the developing branches. This method typically results in fewer, but larger, plants compared to other techniques, as each plant is encouraged to occupy a much wider footprint.
The Mechanics of Light Maximization
The effectiveness of the SCROG method is rooted in plant physiology, specifically the principle of apical dominance. In nature, a plant’s main central stem produces a hormone called auxin, which concentrates at the apex, or highest growing tip. This high concentration of auxin suppresses the growth of lower side branches, giving the plant its typical “Christmas tree” shape.
The SCROG technique actively breaks this dominance by forcing the main stems to bend and grow horizontally, or by removing the main growing tip through pruning. When the apical bud is removed or bent below the height of the side branches, the auxin flow is redistributed, promoting the vigorous growth of multiple side shoots. These new shoots develop into numerous secondary growing tips, or colas, instead of a single dominant one.
By creating a uniform canopy where all tips are equidistant from the light, the plant’s energy is equally distributed among many productive flower sites. This prevents energy from being wasted on lower foliage that would otherwise be heavily shaded.
Essential Tools and Setup
Setting up a SCROG system requires specific materials to build the structural framework necessary for training. The centerpiece is the screen itself, which can be constructed from plastic trellis netting, strong string, wire, or framed PVC piping. The material chosen must be durable enough to support the weight of the developing branches and flowers later in the growth cycle.
The mesh size, or the size of the squares in the screen, is an important consideration, with a spacing of approximately 2 to 4 inches being widely recommended. This size allows enough room to weave the branches through while still providing adequate support and structure for the canopy. The screen must be installed at a fixed height above the growing medium, typically between 8 and 12 inches (20 to 30 centimeters).
This placement ensures the branches can be trained horizontally as soon as they reach the screen during the vegetative phase.
Step-by-Step Implementation and Training
The SCROG process begins early in the plant’s life, often in conjunction with initial pruning techniques like topping. Topping involves cutting off the main stem’s growing tip, which immediately encourages the plant to produce two new main branches below the cut. This early preparation helps create the foundation of multiple main stems needed to fill out the screen horizontally.
Once the plant has recovered from topping and the side branches begin to grow vigorously, the screen is introduced. The vegetative phase is extended to allow the plant sufficient time to grow and spread out across the entire mesh area. As the branch tips grow a few inches above the screen, they are gently bent or “tucked” back down and woven underneath the mesh, directed toward an empty square further away.
This continuous process of tucking and weaving ensures that all new growth is trained sideways to fill the screen. The goal is to fill approximately 70% to 80% of the screen squares before switching the plant to the flowering light cycle. Once the light cycle is changed, the plant will undergo a significant “stretch,” and the remaining screen space will quickly fill, resulting in a perfectly level and maximized canopy of flower sites.