Cannabis Plant Training: LST, Topping, and ScrOG to Maximize Yield
Learn how to break apical dominance and shape your canopy to get the highest possible yield per watt from your indoor space.
Why train your plants?
Left to grow naturally, cannabis adopts a Christmas tree shape with one main top cola (apical dominance) and many shaded, underdeveloped lower buds (popcorn buds). Indoors, where light intensity drops dramatically with distance, this Christmas tree shape is extremely inefficient.
Plant training overrides apical dominance. By bending, cutting, or guiding branches, you distribute growth hormones (auxins) evenly, creating a flat, wide canopy where every bud site is equidistant from the grow light. This dramatically increases both yield and overall bud quality.
Low Stress Training (LST)
Low Stress Training (LST) involves bending the main stalk and side branches and tying them down. Because you are not cutting the plant, LST causes minimal stress and does not stall vegetative growth, making it ideal for autoflowers and young photoperiods.
Start LST early, around week 2 of veg, when stems are still soft and flexible. Bend the main shoot horizontally and secure it with rubber-coated garden wire attached to the pot rim. Side shoots will quickly turn upwards, seeking light, creating a multi-top canopy.
Pro tip
Never use thin string or twist-ties that can slice into the tender stems like razor blades. Always use thick, soft horticultural wire.
High Stress Training (HST): Topping and FIMing
High Stress Training (HST) involves physically removing growth tips. This triggers a hormonal shock that temporarily stalls growth for 2-4 days, but splits the main growth shoot into multiple main branches.
Topping: Cut the main stem completely off between the 4th and 5th node. This removes apical dominance, forcing the two side nodes below the cut to grow into two new main stalks. Only top healthy plants during active vegetative growth.
FIMing ('Fuck I Missed'): Pinch off the top 80% of the main growth tip instead of cutting it clean. This leaves the lower cells intact, which sprout into 3 to 4 new main branches with slightly less stress than a clean top.
Pro tip
Do not top seedlings with fewer than 4 nodes or plants that are already in the flowering stage, as this will severely stunt their yields.
ScrOG (Screen of Green) method
ScrOG involves placing a flat trellis net (usually made of plastic, rope, or string with 3.5″ to 4″ mesh holes) about 12 to 18 inches above the pots. As branches grow up through the screen, you tuck and weave them horizontally under the mesh.
This forces the plant to grow outwards instead of upwards, creating a solid blanket of foliage. Keep weaving during veg until the screen is 70-80% full, then flip to a 12/12 photoperiod. The flowering stretch will fill the rest of the grid with dense, vertical colas.
Use the Light Calculator to check PPFD coverage across your SCROG screenLollipopping and Defoliation
Training is only half the battle. You must clean up the under-canopy to focus energy on the tops. Lollipopping involves removing the bottom 1/3 of all branches, fan leaves, and bud sites prior to flowering.
This lower foliage receives almost no light and only produces loose, leafy popcorn buds. Stripping it improves airflow, lowers relative humidity, prevents mold, and redirects sugars to feed the main colas.
Pro tip
Perform your main defoliation and lollipop on day 1 of flower, and a second light cleanup on day 21 of flower. Avoid stripping leaves late in bloom.
Disclaimer: This article is for educational purposes only. Cannabis laws vary by jurisdiction. Always comply with local regulations.