A cannabis SCROG setup for a 4x4 tent turns one or two plants into a flat canopy that fills all 16 square feet under the light. You mount a horizontal screen 8 to 12 inches above the container, weave each new shoot back under the net as it grows, and keep filling empty squares until the screen is roughly 70 to 80 percent covered. Then you flip to 12/12 and let the buds rise through the net.
how to build a scrog screen for weed
What you need for a 4x4 SCROG
- Tent and light: a 4x4 footprint pairs well with a 400 to 600 watt LED or a 600 watt HID. Match the fixture to the full 16 square feet so the canopy gets even intensity to the corners.
- Containers: one large pot in the 10 to 15 gallon range, or two to four smaller pots if you want to run different plants. Fewer plants means less crowding below the screen.
- Screen material: trellis netting with 3.5 to 4 inch squares, or a DIY frame made from PVC pipe and string. Wider squares are easier to work with when you have big hands.
- Air and climate: an exhaust fan with a carbon filter plus one or two oscillating fans. One fan belongs above the canopy, one below the screen.
- Tools: soft plant ties, garden wire, pruning shears, and a drip tray. A watering wand or small pump helps reach the back of the tent.
Screen height and square spacing
Set the first screen 8 to 12 inches above the rim of the container. Lower than that and you cannot reach under it to water or prune. Higher than that and the plants stretch before they hit the net, which wastes vertical space.
Best Scrog Net for Cannabis Grow: Comparison Review
Square size matters more than most growers expect. A 3.5 to 4 inch grid holds shoots in place without pinching stems. A 6 inch grid lets branches flop sideways and defeats the purpose. If you plan to grow a stretchy sativa, add a second screen 8 to 10 inches above the first for extra support.
When to install and when to flip
- Vegetate until the plant has 4 to 6 main tops and reaches the screen.
- Install the net and start tucking shoots the same week.
- Keep tucking outward and into empty squares. Direct growth toward bare areas rather than letting tops stack in the middle.
- Flip to 12/12 when the screen is about 70 to 80 percent full. Flowering stretch generally adds another several inches of height, and that growth is what finishes the canopy.
Flipping too early leaves gaps you cannot fill. Flipping too late means the canopy crowds itself and airflow drops.
When to Start SCROG Training Cannabis
Building the screen
You can buy a ready-made trellis net or build a frame from half-inch PVC. Cut four legs, join them into a rectangle that matches the tent interior, and drill small holes every 3.5 to 4 inches along each side. Run string or mason line through the holes in both directions to create the grid.
Attach the frame to the tent poles instead of the pot. A screen fixed to the tent stays level when you move or rotate containers, and it keeps the canopy height consistent across the whole 4x4 area.
Training and weaving shoots
Tuck, do not tie, whenever possible. Slide a growing tip under the net and point it toward the nearest empty square. Come back every two or three days during stretch, since shoots can grow an inch or more per day.
- Keep the canopy flat. Any shoot that rises above the net gets bent back under.
- Move outward first, then fill the middle. Corner squares are the last to fill and the easiest to forget.
- Use soft ties only for stubborn branches that refuse to stay down.
- Leave the main stem slightly loose so it can thicken without girdling.
Defoliation and canopy upkeep
Once the screen is full, light stops reaching the lower half of the plant. Remove large fan leaves that sit directly on top of bud sites, and strip growth from the bottom third of the plant, a practice often called lollipopping. Take a little at a time. Leaves drive photosynthesis, so heavy stripping in one session slows the plant for days.
Check under the screen once a week for dead leaves, pests, and trapped moisture. A small clip fan aimed below the net keeps that zone from turning into a mold risk.
Watering and access in a full canopy
A filled screen blocks the top of the pot, so plan your watering route before you start training. Options that work in a 4x4 tent:
- A long watering wand with a curved spout.
- A small submersible pump and hose running to a reservoir outside the tent.
- Blumat-style drip stakes or a gravity-fed drip line.
- Elevated pots over a drain tray so runoff collects in one spot.
Check runoff pH and EC through flower. Salt buildup in a large pot is harder to flush once the canopy is dense.
Common mistakes
- Screen too low or too high. Aim for 8 to 12 inches above the pot rim.
- Too many plants. One or two well-trained plants usually beat four crowded ones in the same footprint.
- Flipping before the screen fills. Gaps at flip time stay gaps at harvest.
- Forgetting the lower canopy. No airflow below the screen invites mold and pests.
- Over-defoliating at once. Spread leaf removal across the first three weeks of flower.
- Ignoring stretch. Indica-leaning plants may double in height, sativas can triple.
Quick checklist
- Set the net 8 to 12 inches above the container.
- Keep squares at 3.5 to 4 inches.
- Tuck shoots every 2 to 3 days during veg and stretch.
- Flip to 12/12 at 70 to 80 percent screen coverage.
- Clean the lower third and keep air moving under the net.
Check your state and local rules before you start a grow. Home cultivation is legal in some jurisdictions and restricted or prohibited in others, and plant counts, tent size, and location rules vary.