Basically, it depends if you're growing inside or out. If you are playing under the lights, then gallon containers would be sufficient (hell, I've seen 16-20 oz cups work for SOG). If you're using mother nature's lighting (the sun), the plant will grow as large as the size of the container allows. Normally, I would use nothing smaller than a 3 gallon container outside (unless you planted late and the plant will be kept under 3 ft.). The lumens are a big contributing factor to the healthy height of the plant. If growing indoors, you want ample light to avoid "stretching", which creates a gangley, weak plant.