A method of training the growing shoots with a trellis, netting, or chicken wire. This method uses very few plants, perhaps one per four square feet, and grows them vegetatively to fill the space needed.
The trellis is held in place 8 to 12 inches above the plant containers, proper spacing should be 2 to 3 inch holes in the trellis. As the growing shoots reach the trellis and poke through the hole, pull them aside to the next hole. Every time a shoot goes through a hole, pull it aside to the next one. Eventually the plant will branch all around the trellis and have growing shoots filling the canopy. Depending on the strain, you start flowering when the canopy is almost full. Then let the buds grow straight through the canopy.
The result is that all of the good growing buds are held in place at equal distance from the light source-- you should get a screen full of top buds. Pruning must be done below the trellis canopy to ensure ventilation. This method is most effective with smaller HIDs and fluorescent tubes since it maximizes the surface area exposed to light while not requiring deep penetration down tall plants.
See also the treatise on SCROG by SCW.
You can comment this FAQ