The Screen of Green (SCROG) technique is a high-yield cultivation method that manipulates the plant’s growth to maximize light absorption. This process involves using a horizontal screen or netting to form a flat, dense canopy where all potential bud sites receive uniform light intensity. Forcing horizontal growth instead of the plant’s natural vertical tendency distributes growth hormones more evenly, creating multiple main colas. The primary goal is to ensure that flowering tops are positioned within the light source’s optimal “sweet spot,” leading to a substantial and homogenous harvest. Implementing this technique requires careful timing and consistent manipulation of the plant’s structure.
Essential Setup and Timing
Establishing the physical screen is the first step, requiring specific materials and placement. The screen is typically made from plastic-coated string, wire, or nylon netting, featuring a grid size of approximately two to four inches (5-10 cm). This grid size allows for easy manipulation and tucking of new growth shoots as the canopy develops. The screen should be fixed horizontally above the growing medium, generally positioned between 12 and 20 inches (30-50 cm) from the top of the pot.
Growers should begin the SCROG process with healthy, well-established plants or clones that have developed several sturdy branches. The screen is introduced early in the vegetative stage, usually once the plant has developed at least four to six nodes and is around 6 to 10 inches tall. Sufficient vegetative time is important because the plant must fill a significant portion of the screen before the light cycle is switched to induce flowering. A longer vegetative phase is often necessary to create the dense, wide canopy required for maximum yield potential.
Training During the Vegetative Phase
To prepare the plant for the screen, initial high-stress training techniques, such as topping or fimming, are often performed. Topping involves removing the main growth tip, typically above the third to fifth node, which eliminates apical dominance. This forces the plant to divert energy and growth hormones into the lateral branches, encouraging the bushy, multi-stemmed structure necessary for SCROG. This manipulation causes the plant to spread outward rather than focusing energy on a single main stem.
Integrating Low Stress Training (LST) is a continuous process that begins as the side branches lengthen. The main branches are gently bent and secured horizontally beneath the screen to coax them into filling the allotted space. As new growth shoots emerge above the netting, the continuous process of “tucking” begins. Each growing tip is carefully woven back underneath the screen and directed toward an open square, forcing the branch to grow horizontally and spread the canopy.
Tucking must be performed regularly, often daily, as the plants grow rapidly to maintain a flat canopy. The goal during the vegetative phase is to fill approximately 70-80% of the screen area with actively growing tips. This strategy ensures there is still room for the rapid vertical growth that occurs after the light cycle is transitioned, preventing the canopy from becoming overly crowded. Once the desired coverage is achieved, the plant is switched to a 12-hour light and 12-hour dark schedule to initiate the flowering phase.
Canopy Management Through Flowering
The transition to a 12/12 light cycle triggers a rapid vertical growth phase, often called the “stretch,” which lasts for the first two to three weeks of flowering. During this period, the plants can double or even triple in height, requiring continued tucking to manage this surge. New growth tips must be continually woven beneath the screen to keep all potential flower sites at a uniform height. Maintaining this flat plane ensures that every developing cola receives intense light exposure from above.
Once the stretch phase is complete and the screen is fully utilized, attention shifts to optimizing energy distribution for bud production. Lower site pruning, commonly known as lollipopping, is performed by removing all small branches and growth below the screen. This technique redirects the plant’s energy reserves away from developing small, airy “popcorn buds” in shaded lower areas. By eliminating this undergrowth, the plant focuses its resources entirely on developing large, dense flowers in the well-lit canopy above.
Strategic maintenance defoliation above the screen is employed to enhance light penetration and improve airflow within the dense canopy. This involves removing large fan leaves that are directly shading bud sites or overlapping excessively, often performed around week three of flowering. Reducing leaf density helps prevent moisture buildup, lowering the risk of mold and pests, while ensuring light reaches deeper into the flower clusters. The screen then provides crucial physical support for the heavy, maturing colas until harvest.