the jew is right, 6" square post will give you 64 plants in a 4x4 under a 1000hps and your in bizz.....4 per square ft is the rule and trim up the bottom 3rd of the plant to lollipop it and increase air flow throughout the grow. if you dont trim it it will be too crowded and mold will put a whoopin on you but properly trimmed sog style plants will work everytime.