ScrOG Guide: How to Screen of Green Cannabis

ScrOG stands for screen of green. You stretch a net or mesh horizontally over your plants and keep weaving the growing shoots under it until the whole canopy sits at one height, close to the light. Every bud site then gets about the same light, instead of one tall cola shading the rest. The price is work: you check and weave the plants almost every day for weeks. We do not recommend ScrOG to beginners, and it is not meant for autoflowers.

This guide covers what a ScrOG does, which plants suit it, how we set up the nets, when to weave, when to flip to 12/12, and the mistakes we see most. Where something is a general fact it has a source. Where it is how we do it, we say so.

Is ScrOG right for you?

ScrOG and low-stress training are not for beginners. If this is one of your first grows, keep the plant simple and come back to the net later. Our guide to low-stress training is a good next step once you have a grow or two behind you. A ScrOG punishes small errors: a late flip, a snapped branch or a damp, dense canopy can cost you a large part of the harvest.

Autoflowers are a poor fit. They run on their own clock, so you cannot hold them in vegetative growth until the net is full, and we do not top them either. We run ScrOG with feminized and regular photoperiod seeds only.

The reward is a flat canopy. Light reaches many bud sites at about the same distance, air moves through the top, and a small number of plants can fill a whole net. If you want that and you are willing to spend a few minutes every day on the plants, read on.

Which plants work best

In our experience hybrids and sativas work well in a ScrOG, and we prefer sativa-dominant strains. They stretch easily, and their long, flexible branches are easier to guide under a net. They also take longer in the growth phase than indica-leaning plants, so plan for more time before the net fills. We do not give a number of weeks, because it depends on the plant, the pot, the light and how hard you top.

Indicas and indica-dominant plants are bushier and shorter. You can use them, but expect a denser canopy that needs more leaf removal and more attention to airflow.

How many plants? We always put as few plants as possible under one net. A plant needs room to do its best, and one well-trained plant with space usually beats several crowded ones. More plants also means more branches to weave and more places for moisture to hide.

AMS strains that suit a ScrOG

For a net you want tall, sativa-dominant or hybrid photoperiod plants, so these four feminized strains from our shop are a good place to look. The figures are the ones on each product page.

• 
  Happy Haze Feminized: 75% sativa, up to 150 cm indoors, flowering time 10 to 16 weeks.
• 
  Kali Jack Feminized: 90% sativa, up to 160 cm indoors, flowering time 8 to 12 weeks.
• 
  Blue Dream XTRM Feminized: 80% sativa, up to 120 cm indoors, flowering time 8 to 12 weeks.
• 
  Chocolope Feminized: 90% sativa, up to 150 cm indoors.

Tall plants fill a net with fewer stems, but they stretch a lot, so they need an early switch to 12/12 (we explain the 75% rule below) and a bare bottom.

Setting up the nets

We hang two or three nets, between 30 and 50 cm above the pots. The upper nets have a mesh of 5 by 5 cm and the lowest net is finer. We leave 6 to 12 cm between the nets. Squares of 5 by 5 cm are big enough to pull a shoot through and small enough to give each branch its own square.

Build the frame from timber or PVC pipe, a little smaller than the grow space, with the net stretched tight. A sagging net defeats the purpose. If you are unsure of the size, go slightly larger rather than smaller, because an oversized net is easier to live with than a cramped one.

Light and air are part of the setup. In the growth phase we run 18 hours of light and 6 hours of dark, and in flower 12/12. Keep the lamps high at first, especially with cuttings, and let the roots establish. We sometimes add a root stimulator here. Once the plants reach about 20 to 25 cm, bring the lamps down, but not so low that the tips burn. We keep the air moving and keep the room under slight negative pressure with intake and extraction so the smell stays inside.

The gap between the lowest net and the pots matters. Air has to move through it, and it should be as free of leaves as you can make it and, above all, clean.

Weaving in the growth phase

As the plants grow, tuck the shoots under the net again and again, and guide each one into its own square. Cannabis branches do not climb like vines, so every shoot has to be placed by hand. Do it gently. If a branch resists, leave it for another day and try again.

Our rule for the flip: when the net is about 75% full, switch the lights to 12/12. The plants will keep stretching after the switch, so the last quarter of the net fills itself. It is a mistake to wait for a net that looks completely full, because once the plants stretch you will have buds crowded on top of each other. This general behavior is documented: flowering in photoperiod cannabis is usually triggered by dropping to 12 hours of light and 12 of darkness (Plants, 2023), and plants often grow a lot in the first one to two weeks afterwards, described as the pre-flowering stretch (overview of cannabis cultivation). How much your plant stretches depends on the genetics.

Keep weaving after the flip, until flowers start to form. If one shoot races far above the rest, pinch it back.

Bending and broken branches

We bend and place branches at the end of the day, when they are more flexible and less likely to snap. If a branch does crack, tape it if the break is clean and not too severe. Otherwise cut it off cleanly. Do not leave a hanging branch to rot.

Stop adjusting once flowers form

As soon as the flowers form, stop making adjustments. Bending a branch that carries flowers bruises the tops, and damaged flower tissue is where rot can start. Utah State University Extension lists preventing injury to the flower buds as a basic step against bud rot in hemp (USU Extension).

Clearing the bottom

Remove the leaves under the net. We cut the lower part bare shortly before or around the flip to 12/12. Growth down there never reaches the light anyway, and leaves and small branches in that zone hold moisture and block air. That is what keeps the zone under the net open and clean.

Humidity and bud rot

A full ScrOG canopy is dense, and dense flower is where bud rot (gray mold, Botrytis cinerea) tends to start. Utah State University describes the pattern in hemp: cool conditions, high humidity and moisture on the plant favor the fungus, and prolonged greenhouse humidity during bud formation is a risk. USU recommends keeping greenhouse humidity below 50% and says an infection cannot be cured, so prevention counts (USU Extension).

A 2025 study in Frontiers in Plant Science compared low canopy humidity (37 to 58%) with high humidity (78 to 98%) in one CBD-dominant cannabis cultivar. Under high humidity flowering was delayed by about three weeks and cannabinoid levels fell (Corredor-Perilla et al., 2025). It was one cultivar and the study did not look at bud rot, so it supports the general point and nothing more specific.

This is what we do. We aim for about 50% humidity in early flower, about 30% in advanced flower and about 20% at the end of flowering. The 30% and 20% figures are our own experience. They are lower than most published advice, and we found no university source that recommends 30% or 20%. None of the figures are exact: the real value drifts a few points either way, and the weather plays a part, because rainy weather raises the humidity in the room. Temperature changes how humidity affects a plant too, so treat our figures as a starting point to compare with your own room and your own plants, and watch the plants. Whatever target you use, a hygrometer in the canopy zone, a fan that moves air through the net and a bare bottom matter more than any single number.

Check your buds regularly for rot. USU advises removing infected plants immediately to reduce the spread of spores, and disinfecting tools and the space afterwards.

The mistakes we see most

• Flipping to 12/12 too late. This is the main one. A net that is already completely full before the flip leaves no room for the stretch.
• Breaking shoots and branches while weaving, usually by forcing them or working with dry, stiff plants.
• Bud rot in the top of a dense canopy, often after humidity was left too high.
• Too many plants under one net.
• Adjusting branches after flowers have formed.

Combining ScrOG with other training

In our experience, ScrOG works well with topping, low-stress training, main-lining and super cropping. Topping early gives you more shoots to spread across the net. Low-stress training helps you bend side branches outward before they reach the net. Main-lining builds a symmetrical set of stems that fit a net well. Super cropping, where you pinch and bend a stem until it softens without breaking, should be done in the growth phase and well before the plant reaches the net.

Final thoughts

A ScrOG is a patient way to grow. Start with as few plants as you can, give them room, fill about three quarters of the net before the flip, weave until flowers form, and then leave the plants alone and watch the humidity. If you are new to growing, get a grow or two behind you with simple plants first, then try topping and low-stress training.