The moon controls the movement of water ie the tides, well if the moon is in the wrong phase when you are trying to germinate your seeds they won't do so well. An example would be trying to grow the plant when the water is going out of the plant, the tide is going out.. The moon effects the water in your plant just like it effects the tides. So if you watch the moon and plant and harvest by the moon you yield more and better plants.

Hope this helps. if ya don't believe me try it.