though there are traits that are strain dependent, you can ensure the maximum density of your flowers by limiting the temperature fluctuations as much as possible. When there are dramatic changes in the temperature it causes the fluids within the plant to expand and contract, stretching them out. Say for example you were able to keep a temperature of 70 degrees in a room for the entire grow with 0 fluctuation, provided the plant was fed sufficient nutrients, maximum density would be obtained for that temperature. The lower you can keep the temp without stressing the plant out the more dense the end result will be.