There are some nutes that some people swear by, but the only one that I believe because I have seen it done is through cloning. Supposedly every time you clone a plant the THC content goes up slightly. This is where the strain G-13 comes from, its the 13th clone of the oringinal strain. It also has alot to do with when you harvest the bud as far as trichome color goes. Just my two cents im sure there are things that I havent mentioned or dont even know about...