SCROG Method (Screen of Green): How to Maximize Cannabis Yields

The Screen of Green technique forces your canopy flat, puts every branch tip at the same distance from your light, and converts wasted vertical space into dense, productive bud sites.

What Is the SCROG Method?

SCROG — Screen of Green — is a horizontal training technique that uses a rigid or semi-rigid mesh screen suspended above the plant canopy. As the cannabis plant grows and branches extend upward through the mesh openings, the grower weaves each branch horizontally rather than allowing it to grow straight up. Over two to four weeks of vegetative training, this creates a wide, flat canopy where every branch tip sits at approximately the same height and receives the same intensity of light from the grow lamp above.

The core principle is light efficiency. A cannabis plant left to grow naturally concentrates most of its upper foliage at the apex, directly under the light. The lower and outer branches receive progressively less light intensity and produce smaller, less dense flowers. By flattening the canopy with a SCROG screen, the grower eliminates this intensity gradient. The result is that the entire canopy footprint — not just the central apex — becomes a productive bud-producing zone.

SCROG is considered an intermediate technique. It requires understanding of plant structure, patience during the training phase, and discipline in timing the switch to flower. Growers who master it consistently report it as one of the highest-yield methods available without significant equipment investment beyond the screen itself.

SCROG vs. Sea of Green (SOG)

SCROG vs. LST vs. Topping

Equipment and Screen Setup

The screen is the only piece of equipment specific to SCROG. Everything else in your grow setup remains the same.

Screen material options:

• Nylon string or paracord: The most popular choice among home growers. Cheap, easy to cut away at harvest, and available in any hardware store. Tie a grid of 5 to 7 cm squares across a wooden or PVC frame.
• Wire mesh (galvanised or coated): More rigid and reusable. The rigidity helps with heavier branches during late flowering. Ensure any metal mesh is coated to prevent rust in humid grow environments.
• Pre-made SCROG nets: Available from grow equipment suppliers in standard tent sizes. Convenient but often use larger mesh openings (10 cm) that give less control over branch placement.

Screen specifications:

• Mesh opening size: 5 to 10 cm (2 to 4 inches) — 5 to 7 cm preferred for precision training
• Screen height above pot: 40 to 60 cm (15 to 23 inches)
• Frame material: Wood dowel, PVC pipe, or tent support poles — the frame must be stable enough to support branch weight during late flowering (up to several kilograms per plant)
• Screen should cover the full floor area of the grow tent to maximise usable canopy space

The Weaving Technique

Weaving is the core physical skill of SCROG training. The process continues for several weeks during the vegetative phase and requires visiting the grow space every one to two days.

As each branch tip grows up through a mesh opening, rather than allowing it to continue growing vertically, the grower gently bends it horizontally and tucks it under the next mesh opening in the desired direction. The branch tip now points outward rather than upward, and a new lateral shoot will quickly emerge from the bend and grow upward through the next available opening.

Key weaving principles:

• Always weave toward empty screen space, not toward already-filled areas
• Younger, flexible branches weave easily without risk of snapping. Older, woody growth may resist — never force a branch to the point of cracking
• Weave evenly across the entire screen surface. Avoid letting one side fill while another remains empty
• After each weaving session, step back and look at the whole canopy from above. Identify thin areas and redirect nearby branches to fill them

When to Flip to Flower: The 70-80% Rule

Timing the switch from vegetative to flowering light schedule (12 hours light / 12 hours dark) is the most consequential decision in any SCROG grow. Flip too early and you waste canopy potential. Flip too late and explosive flowering stretch causes unmanageable overgrowth above the screen.

The standard guidance is to flip when 70 to 80 percent of the screen surface is filled with woven branches. This accounts for the stretch that cannabis plants undergo in the first two to three weeks after the flip. Most strains will add 50 to 100 percent of their current height during flowering stretch, and some sativa-dominant varieties can stretch 150 to 200 percent. When the stretch fills the remaining 20 to 30 percent of the screen, the canopy reaches full saturation at exactly the right point in flowering development.

After the flip, continue tucking branches that grow through the screen for the first two to three weeks of flowering. Once the plant has committed to flower development and growth slows, stop all training to avoid stressing buds.

Lollipopping After Screen Fill

Once the screen is fully filled and the plant has been flipped to flower, lollipopping becomes highly beneficial. Lollipopping refers to the removal of all foliage and bud sites below the SCROG screen — everything that will not receive adequate light because it is shaded by the canopy above.

This removes growth that would consume nutrients and energy without producing viable buds. The plant’s resources are now directed exclusively to the upper canopy sites that are receiving full light intensity. Well-executed lollipopping visibly improves bud density on the upper colas in the final weeks of flowering.

Perform lollipopping in two stages: once immediately after the flip (remove the lowest, weakest growth) and a second time at week two or three of flowering (remove anything clearly below the canopy that has not developed significant bud structure). Avoid heavy defoliation late in flowering as the plant needs some leaf mass for photosynthesis.

Expected Yield Data

SCROG consistently outperforms untopped, untrained plants in yield per square metre. The improvement derives entirely from light efficiency: the same wattage illuminates a productive canopy surface rather than being partially wasted on an uneven, single-apex structure.

Grower data and controlled grow comparisons suggest the following ranges:

• Untopped single-cola plant (600W HPS, 1.2m x 1.2m): 200 to 350g
• Topped plants without SCROG (same setup): 300 to 500g
• SCROG-trained plants (same setup, 70-80% screen fill at flip): 400 to 600g+

The combination of topping before SCROG training and a correctly filled screen at the flip point consistently delivers the highest results in this range. Individual results vary with strain genetics, light quality, nutrition programme, and environmental conditions.

Best Strains for SCROG

Common SCROG Mistakes

• Flipping too early: Switching to flower before the screen is 70 percent filled means you harvest a partially filled canopy, wasting most of the light footprint and undershooting yield potential.
• Wrong screen height: A screen positioned too low restricts plant development. Too high and branches fail to hold their trained position. The 40 to 60 cm above pot guideline works for most strains; adjust higher for tall sativa-dominant genetics.
• Insufficient defoliation: Allowing a thick mat of fan leaves to develop above the screen shades lower bud sites. Strategic defoliation during weeks 3 to 5 of flowering improves light penetration to mid-canopy bud sites.
• Training in late flower: Weaving or bending branches after week 3 of flowering damages developing buds and stresses the plant at exactly the wrong phase of its life cycle. All training should be complete by week 3.
• Neglecting airflow: A dense, full SCROG canopy can impede air movement, creating humid stagnant zones that promote mould and mildew. Ensure oscillating fans circulate air both above and below the screen.

Frequently Asked Questions

What is SCROG?

SCROG stands for Screen of Green. It is a cannabis training method that uses a horizontal mesh screen positioned above the plant canopy. As branches grow up through the screen, the grower weaves them horizontally to create a flat, even canopy that maximises the area receiving direct light from the grow lamp above.

How full should a SCROG screen be before flipping to flower?

The screen should be 70 to 80 percent filled with woven branches before switching to a 12/12 flowering light schedule. Flipping earlier leaves unused canopy space and reduces final yield. Flipping after the screen is overfilled risks unmanageable flowering stretch that blocks airflow and creates humid microclimates ideal for botrytis.

Does SCROG increase yield?

Yes. SCROG typically produces 20 to 30 percent higher yields than untopped plants in the same footprint because it ensures that every square centimetre of the canopy receives direct light rather than only the apex. Combined with topping, the improvement can exceed 50 percent over single-cola untrained plants.

How many plants for a SCROG setup?

In a 120 x 120 cm tent, most growers use 1 to 4 plants under a single SCROG screen. Fewer plants with more vegetative time and pre-topping can fill the screen just as effectively as more plants, and may be preferable in jurisdictions with plant count restrictions. One large, well-topped plant can fill a 120 x 120 cm screen in approximately 6 to 8 weeks of training.

SCROG Training Schedule: Week-by-Week Overview

Understanding the rhythm of a SCROG grow from seed to harvest helps growers plan their vegetative period correctly and avoid the most common timing errors.

Weeks 1 to 3 (Pre-screen): Germinate, establish the seedling, and allow the plant to develop 5 to 7 nodes. Top once or twice during this period to initiate multi-cola branching. The plant is not yet interacting with the screen — focus entirely on root zone establishment and healthy vegetative growth.

Week 3 to 4 (Screen installation): Install the screen at 40 to 60 cm above the pot rim. The plant’s current canopy should be at or below the screen height. This is the correct installation timing — branches are still short enough to begin weaving immediately without forcing or stressing established growth.

Weeks 4 to 7 (Active weaving): Visit the grow space every 1 to 2 days. Weave each branch that extends through a mesh opening horizontally toward empty screen space. The screen should fill gradually and evenly. Maintain nutrient and water schedules appropriate for vigorous vegetative growth.

Weeks 6 to 8 (Flip assessment): Monitor screen fill percentage. When 70 to 80 percent of the screen surface is covered with woven branch tips, prepare to transition to flower. Do a final check of plant health, root zone condition, and environmental parameters before the flip.

Flower weeks 1 to 3 (Stretch management): Continue tucking any new growth above the screen as the plant stretches. Perform lollipopping in two stages. This is the final active training period. Once vertical growth plateaus, all physical canopy intervention stops.

Flower weeks 4 through harvest: Hands-off management. Focus on nutrition (transition to bloom ratios), environmental conditions (lower humidity to 40 to 50 percent for mould prevention), and monitoring trichome development for harvest timing.

SCROG in Legal Markets: Plant Count Considerations

In jurisdictions where home cultivation is legal but plant counts are restricted — commonly 2 to 6 plants per household — SCROG offers a significant strategic advantage. Because SCROG achieves maximum yield from a small number of plants rather than from plant volume, growers in these markets can extract the maximum legal production from their permitted plant count.

A single well-managed photoperiod plant in a 120 x 120 cm tent, topped three times and trained under a full SCROG screen, can produce yields equivalent to 4 to 8 untrained plants in the same space. This makes SCROG not just a yield-maximizing technique, but a legally optimal cultivation strategy in restricted-count markets.

The trade-off is time: one large SCROG plant needs 6 to 10 weeks of vegetative training to fill its screen, while multiple smaller plants in a SOG setup flower much sooner. Growers must weigh the value of their time versus their plant count limit when choosing between these approaches.

Diagnosing SCROG Problems Mid-Grow

Even experienced growers encounter problems in SCROG grows. Knowing how to identify and respond to common issues mid-train prevents minor setbacks from becoming crop failures.

Uneven screen fill: One side of the screen fills faster than the other, creating an imbalanced canopy. Cause: uneven branch distribution in early weaving, or asymmetric topping that created more branches on one side. Fix: actively redirect over-performing branches toward the thin side of the screen and slow down weaving on the full side for 3 to 5 days.

Branches snapping during weaving: Woody, older growth resists bending and snaps when forced. Cause: training too late on established stems. Fix: support snapped branches with soft plant ties and tape if partially attached — they often recover. In future, weave earlier when growth is still flexible.

Screen overcrowding before 70 percent: The screen appears full but the plant has only been in training for 2 to 3 weeks. Cause: too many plants for the screen size, or a very vigorous strain. Fix: begin the flip assessment early and flip at first 70 to 75 percent fill rather than waiting for 80 percent.

Mould developing under the screen: White or grey fuzzy growth appearing on stems below the canopy. Cause: insufficient airflow beneath the screen combined with high humidity. Fix: increase extraction fan speed, add a fan directed under the canopy, and perform lollipopping immediately to open up airflow at the base of the plant.

Nutrient Management in a SCROG Grow

Nutrient management in a SCROG grow follows the same general principles as any cannabis cultivation, but the extended vegetative period and large canopy create some specific considerations that are worth addressing explicitly.

During the vegetative training phase, the plant’s demand for nitrogen is high and consistent. It is producing large amounts of leaf and stem tissue to fill the screen. A standard vegetative formula (higher N, moderate P and K) at the recommended dilution rate for your chosen nutrient line is appropriate throughout this phase. Pay close attention to any yellowing of lower leaves, which may indicate that the plant is mobilising nitrogen from older tissue to feed the rapidly growing new branches.

In the final week of vegetative training, before the flip to flower, many experienced SCROG growers perform a light flush (plain pH-adjusted water for 1 to 2 days) to reset the root zone and prepare for the transition to bloom nutrients. This is not universal practice, but it provides a clean baseline from which to introduce the higher phosphorus and potassium ratios appropriate for the flowering phase.

During late flowering (weeks 6 through to harvest), a gradual reduction of nutrients to plain water — commonly called flushing — is widely practised to clear residual salts from the growing medium before harvest. The effectiveness and necessity of flushing is debated, particularly in soil grows, but the approach causes no harm if water quality is good and the plant is not stripped of nutrients too early.

SCROG for Autoflowering Strains: Is It Worth It?

Autoflowering strains and SCROG training have a complicated relationship. The conventional guidance is that SCROG is best suited to photoperiod strains, and this remains largely true for most home growers. However, experienced cultivators do achieve excellent results running autoflowering genetics under a screen, provided they understand the constraints.

The fundamental challenge is time. Autoflowering strains begin flowering automatically at 3 to 5 weeks of age regardless of light schedule, leaving a very narrow window for vegetative training. To fill even a modest 80 x 80 cm screen before flowering begins, the grower must start weaving aggressively at week 2 or 3 and rely on a high-vigour strain that branches rapidly without topping.

Topping autoflowering strains before or during SCROG training is technically possible but high-risk for beginners. The recovery time required after topping (5 to 10 days) may consume a significant portion of the available vegetative window. LST combined with a screen — weaving without any cutting — is a lower-stress approach that achieves partial canopy flattening without the recovery time penalty.

If running autoflowers under a screen, choose genetics specifically bred for vigour and fast vegetative growth: strains like Gorilla Glue Auto, White Widow Auto, or AK-47 Auto are better candidates than compact or slower-growing auto varieties. Use a smaller screen (60 x 60 cm) that can be filled with fewer branches and in less time. Accept that the screen fill will likely reach 50 to 60 percent rather than 70 to 80 percent, and flip to flower (i.e., continue on 20/4 light) based on plant age rather than screen fill.

Light Burn and SCROG: Managing Canopy Distance

A filled SCROG screen sits at a fixed height below the grow light, creating a uniform light-to-canopy distance across the entire growing area. This uniformity is one of SCROG’s primary advantages, but it also means that if the canopy rises above the screen during flowering stretch, the distance to the light decreases — potentially causing light burn or heat stress on the tops of the tallest colas.

The risk is highest with fast-stretching sativa-dominant strains in small tents where there is limited headroom between the screen and the light fixture. To manage this:

• For sativa-dominant strains, install the screen 5 to 10 cm higher than you would for indica genetics, giving more buffer for flowering stretch above the screen level
• Flip to flower at 60 to 65 percent screen fill (rather than 75 to 80 percent) when growing fast-stretching varieties, allowing the stretch to complete the fill rather than overfilling the screen
• Continue tucking during the first 3 weeks of flower to keep colas from growing straight up and reducing light distance
• Raise the light fixture if possible during peak stretch (flower weeks 1 to 3) and lower it again once vertical growth stops

Modern LED quantum boards with dimmer controls offer an additional option: reducing lamp intensity by 10 to 20 percent during the most active stretch period reduces light burn risk without requiring physical adjustment of the fixture height. Restore full intensity once the canopy has stabilised.

Recording Your SCROG Grow: Why Data Matters

Keeping a grow journal through a SCROG cycle transforms each grow into a learning tool for the next. At minimum, record: screen fill percentage at each weaving session, date of flip, date lollipopping was performed, weekly plant height above the screen, any environmental anomalies (temperature spikes, humidity excursions), and final dry weight at harvest.

With even 2 to 3 harvests of data from the same strain in the same setup, patterns emerge that would otherwise be invisible: which strains fill the screen fastest, at what fill percentage the flip produces the best final canopy, how many weeks of flowering the specific plant ran before peak trichome development. This data eliminates guesswork from the most consequential decisions in the grow and consistently improves results over time.

Simple grow journals can be kept in a notes app, a spreadsheet, or a physical notebook. Photography is particularly valuable — photographing the canopy from above once per week during training makes screen fill percentages objective rather than estimated, and creates a visual record that is impossible to replicate from written notes alone.

Summary: SCROG Method Key Points

SCROG is the most light-efficient training method available to home growers working with photoperiod cannabis plants. Its yield advantage is structural and reliable: by forcing every branch tip to the same height under the screen, the grower converts a light-inefficient conical plant into a light-efficient flat canopy where every square centimetre produces viable, dense buds. The technique requires patience, consistency during the weaving phase, and disciplined flip timing at 70 to 80 percent screen fill. For growers willing to invest the vegetative time, SCROG consistently delivers among the highest yields per watt of any indoor growing method.

Begin with a single topped plant in an 80 x 80 cm or 120 x 120 cm tent, a simple nylon cord screen, and a reliable strain with documented vigorous growth response to training. Document your training sessions, photograph the canopy weekly, and record the flip date and final dry weight. With two or three SCROG cycles of data, the timing intuition that separates average from exceptional results becomes second nature.

Jordan Price

Senior Cannabis Cultivation Editor at ZenWeedGuide. Jordan covers high-stress and low-stress training techniques, grow room optimisation, and strain-specific cultivation guides. All content is verified against current horticultural research and grower field data.