GenetixBayEST. 2009
Training · Intermediate · 2 min read

SCROG: screen of green

SCROG uses a horizontal net 20–40 cm above the pots to spread a few plants into a flat, even canopy: shoots are tucked under the net through veg and early stretch, then allowed to grow up through it. It suits small rooms and plant-count limits, at the cost of longer veg. Fill about 70–80 % of the net before flipping, since plants stretch to fill the rest.

Grower practice
Draft: awaiting expert review Updated
VegTransitionFlowerAny system

Short answer. Fix a net (5–10 cm / 2–4 in squares) 20–40 cm (8–16 in) above the pots. Through veg, tuck every shoot that pokes through back under, sideways, so the plant spreads across the screen. Flip to 12/12 when the net is ~70–80 % full; tuck for the first ~2 weeks of stretch, then let tops grow up. Below the net, strip small shaded growth (lollipopping). SCROG makes few plants fill a space evenly, which helps under plant-count limits; it trades extra veg time and labour for that. Head-to-head yield vs SOG is not published; light and canopy evenness drive both [1][3].

How to do it

  1. Top once or twice, then LST the branches outward (topping, LST).
  2. Install the net before the plant reaches it; make it taut and level.
  3. Tuck daily or every other day; always tuck sideways along the net.
  4. Flip at 70–80 % fill; tuck for 10–14 days of stretch.
  5. Around day 21 of flower, remove growth below the net that gets little light.
  6. A second net 20–30 cm higher supports heavy colas.

Numbers that matter

Item Typical
Net height above pots 20–40 cm (8–16 in)
Net mesh 5–10 cm (2–4 in)
Plants per m² 1–4 (1 per 0.25–1 m²)
Veg time 4–8 weeks depending on pot size and space
Fill at flip ~70–80 %
Stretch Many cultivars stretch 1.5–2.5× after flip (Grower practice)

Common mistakes

  • Flipping with a full net, then running out of space in stretch.
  • Tucking upward or twisting stems.
  • Leaving dense, dark growth under the net (larf and mould risk).
  • Too few plants for the space under a plant-count-free setup (longer veg = more power).

Evidence

The canopy-light rationale is Supported [1]; planting density strongly affects yield per area and uniformity [2][3]. SCROG technique and fill rules are Grower practice.

Questions this article answers

How does SCROG work?

SCROG uses a horizontal net 20–40 cm above the pots to spread a few plants into a flat, even canopy: shoots are tucked under the net through veg and early stretch, then allowed to grow up through it. It suits small rooms and plant-count limits, at the cost of longer veg. Fill about 70–80 % of the net before flipping, since plants stretch to fill the rest.

How high should the SCROG net be?

SCROG uses a horizontal net 20–40 cm above the pots to spread a few plants into a flat, even canopy: shoots are tucked under the net through veg and early stretch, then allowed to grow up through it. It suits small rooms and plant-count limits, at the cost of longer veg. Fill about 70–80 % of the net before flipping, since plants stretch to fill the rest.

When do I flip a SCROG to flower?

SCROG uses a horizontal net 20–40 cm above the pots to spread a few plants into a flat, even canopy: shoots are tucked under the net through veg and early stretch, then allowed to grow up through it. It suits small rooms and plant-count limits, at the cost of longer veg. Fill about 70–80 % of the net before flipping, since plants stretch to fill the rest.

SCROG vs SOG: which yields more?

SCROG uses a horizontal net 20–40 cm above the pots to spread a few plants into a flat, even canopy: shoots are tucked under the net through veg and early stretch, then allowed to grow up through it. It suits small rooms and plant-count limits, at the cost of longer veg. Fill about 70–80 % of the net before flipping, since plants stretch to fill the rest.

How many plants for a SCROG?

SCROG uses a horizontal net 20–40 cm above the pots to spread a few plants into a flat, even canopy: shoots are tucked under the net through veg and early stretch, then allowed to grow up through it. It suits small rooms and plant-count limits, at the cost of longer veg. Fill about 70–80 % of the net before flipping, since plants stretch to fill the rest.

Sources

  1. Rodriguez-Morrison V, Llewellyn D, Zheng Y, 2021. Cannabis yield, potency, and leaf photosynthesis respond differently to increasing light levels in an indoor environment. Frontiers in Plant Science 12:646020. doi.org/10.3389/fpls.2021.646020
  2. Danziger N, Bernstein N, 2022. Too dense or not too dense: higher planting density reduces cannabinoid uniformity but increases yield/area in drug-type medical cannabis. Frontiers in Plant Science 13:713481. doi.org/10.3389/fpls.2022.713481
  3. Backer R, Schwinghamer T, Rosenbaum P, et al., 2019. Closing the yield gap for cannabis: a meta-analysis of factors determining cannabis yield. Frontiers in Plant Science 10:495. doi.org/10.3389/fpls.2019.00495

Related

Grower practiceBeginner · Draft

LST: low-stress training

Low-stress training bends and ties stems outward and down so the plant grows as a flat, even canopy, without cutting anything. It is the safest training method, suits autoflowers, and works with topping and SCROG. Start in early veg, adjust ties every few days, and stop bending hard once stems lignify in mid-stretch.

SupportedBeginner · Draft

Topping: cutting the main tip for more colas

Topping removes the main growing tip above a node so the two shoots below take over, breaking apical dominance and producing a flatter plant with more main colas. Top healthy plants with 4–6 nodes, cut just above the chosen node, and allow 5–10 days of recovery before flipping to flower. In one controlled study, pruning twice (at transplant and at the switch to flower) gave the highest flower and cannabinoid yield per plant.

SupportedIntermediate · Draft

SOG: sea of green

Sea of green packs many small plants, usually clones, into the space and flowers them after little or no veg, so each plant makes one main cola. Higher planting density increases yield per square metre but lowers cannabinoid uniformity between plants, according to controlled research. Typical densities are 9–25 plants per m² with 0–14 days of veg; check local plant-count rules first.

SupportedIntermediate · Draft

Defoliation and lollipopping: what to remove, when, and the evidence

Lollipopping strips small branches and leaves from the shaded lower third at or near the flip; defoliation removes fan leaves that shade bud sites or block airflow. In a controlled study on large plants, neither defoliation three weeks before harvest nor lower-branch removal changed flower or cannabinoid yield per plant, and defoliation improved cannabinoid uniformity. Stripping within reason doesn't hurt yield, but in the founder's experience tucking helps more: tuck and train first. Whether tucking beats stripping, and whether defoliation raises cannabinoids, is an open GenetixBay trial question.

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