Here at Big Buds Magazine, we’ve gone deep on screen of green (SCROG) marijuana growing, a favorite technique for growers who want to get large yields from fewer plants.
Previously, we’ve explained the advantages and disadvantages of scrogging, the ideal SCROG root zone, feeding and lighting SCROG plants, how to physically support SCROG plants, and choosing the best strains for SCROG growing.
Now, let’s deal with the most hands-on and crucial aspect of scrogging — low stress training, commonly referred to as LST.
LST is the nuts and bolts of scrogging. It involves minor trimming of marijuana plants, along with manipulating branches so they’re supported by and grow through a horizontal screen.
Some SCROG gardens use minimal low stress training. The marijuana plants are allowed to grow vertically as they naturally would, but vertical growth is channeled through a screen to provide branch support.
SCROG gardeners who want higher yields trim their plant’s topmost growth tip and channel lower branches through the screen with varying degrees of horizontal training to spread the plant canopy wide rather than tall.
LST and SCROG processes are best learned practically. For that reason, we’ve sourced the most easy-to-follow videos to show the tried and tested techniques you can adapt for your gardening situation, plus given you a written summary. We suggest you watch all the videos before you make decisions about how you want to run your SCROG garden.
Helpful Tips For LST Scrogging
You can LST clones or seedlings. Make sure you’re growing only feminized marijuana seeds if you’re starting plants from seed.
After your clones or seedlings have 5–7 sets of true leaves, trim the top apical growth shoot. This creates physiological and hormonal changes in the plant that push growth to lower ancillary stems off the main stalk.
Three days after you’ve trimmed the apical growth tips, place the horizontal screen over the plants and let the branches grow into the screen. The distance between a SCROG screen and your plant canopy depends on what week of grow or bloom phase the plants are in, how fast they’re growing, and how much more length you expect buds and branches to grow.
My general approach is to place the first screen so there’s at least eight inches between the top of the plant canopy and the first screen. If I stack several screens on top of each other to provide several feet of vertical screen support, I may leave eight inches or more between each screen, depending on the factors previously mentioned. Some growers prefer a larger gap than that.
As branches grow taller and butt up against the screen, separate them from each other, pulling them away from the main stem to create as close to a 360-degree horizontal growth pattern as you can. You can weave the growing branches into and through the screen, and in some cases you’ll use plant tape (a soft tape used to bind plants and support them) to ensure branches are properly placed in and throughout the screen.
Some growers simply distribute branches through the square holes in their SCROG screen, with minimal attempt to pull and place branches. This is an easier technique than bending, pulling and tying, and uses the screen as a gentle support for vertically oriented buds. If you have several plants, and limited horizontal area but adequate vertical height, this might be your best strategy. If you have only a couple of plants, lots of horizontal space, and limited vertical height, force the branches horizontal for a few days to spread them out, before allowing them to resume natural vertical growth.
Be careful when you pull and train branches, but if they break or snap, gently join them back together, then wrap plant tape around them to close the wound. If your plants are healthy, the broken branch will heal itself. However, if the branch has broken completely in two, healing is very unlikely if not impossible.
Using LST, you often need longer in grow phase than is typical because you’re stressing the plants, which temporarily slows growth rate. Instead of my usual 4–5 weeks in grow phase, with SCROG I’ll go 5–7 weeks in grow phase.
However, you must always be conscious that at the start of bloom phase, cannabis plants go into a growth spurt that can double branch length. Plan for the bloom-phase growth spurt as you size and place your screen, as you decide how long your plants should be in grow phase, and as you place your branches into the screen. Growers in outdoor gardens using SCROG LST techniques with unlimited height often place multiple stacked screens about every two feet to support buds that can grow as large as baseball bats!
After 3–4 weeks in bloom phase (depending on the strains you’re growing), your branches have likely ceased most if not all their linear growth and will be at their ideal length. At the same time, developing buds will be growing vertically through and above the screen.
Some leaves will get in the way of light penetration, air movement, bud fattening and branch fastening, so they should be removed. But excessive leaf removal damages plants and can delay flowering and floral maturation. In general, it’s best to stop removing leaves after week-two bloom phase, and to never remove more than 15 percent of all leaf mass at one trimming.
It’s useful to lollipop your plants. Lollipopping means removing the bottom branches growing near the root zone that will never get direct light penetration. Do this in the final two weeks of grow phase, and know that your plants will need time to recover.
One of your main goals as you trim and weave your branches is to keep an even canopy. You want your buds to be at roughly the same height across the screen plane. If they’re not, your light penetration will be uneven and bud production will suffer.
Be sure to have strong fans pushing lots of clean, carbon-scrubbed air through the underside of the horizontal canopy. Ensure good grow-room exhaust ventilation, plus control of relative humidity. SCROG branches are crammed next to the screen, and to each other. They need lots of air movement and air exchanges so you avoid an environment in which gray mold, diseases and insect invaders can thrive.
Because LST and SCROG is a high-stress process, feed your plants B-complex vitamins found in such products as B-52, a known stress-buster for plants.
During grow phase and until primordial flowers develop, foliar spray your SCROG plants with a 5.7 pH, 160 ppm solution combining equal parts Rhino Skin (which contains potassium silicate) and B-52.
After you’ve flipped to bloom phase lighting, and until early flowers develop, add Bud Ignitor to the foliar spray, using all three products in equal amounts and maintaining 5.7 pH and 170 parts per million. Spray when the lights are off and use only reverse osmosis water. Be sure to spray the undersides of leaves, not just the top surfaces. Spray no more than twice a week.
Harvesting SCROG plants is more time-consuming and has different logistical challenges compared to cannabis plants grown without LST. You’ll have a horizontal plane filled with spiky colas arising from the woven branches. You won’t be doing a main stalk cut-and-hang when you’re growing LST SCROG plants. Rather, you’ll be cutting individual buds and in some cases unfastening buds from the screen. Use a drying rack for your buds.
Yes, the SCROG technique is a labor-intensive cannabis-growing method involving extra equipment and skills above and beyond regular marijuana growing.
But as with bonsai gardening and topiary, training marijuana plants is an interesting, relaxing, pleasurable activity. It’s a way of creating living sculpture. And the wonderful payoff is that SCROG marijuana growing gives you large yields from a handful of cannabis plants. It’s definitely worth trying at least once.