In keeping with Isaac Newton’s law of gravity, the Earth is influenced by the gravitational pull of the moon. The tides are highest at the time of the new and the full moon.
 
Just as the moon pulls the tides in the oceans, it also pulls upon more subtle bodies of water, causing moisture to rise in the soil (and in seeds), which encourages germination and growth. The highest amount of moisture is in the soil at this time, and tests have proven that seeds will absorb the most water at the time of the full moon.