A couple of years later, now in grad school, I told the stories of Don Juan and my father-in-law to a Colombian plant physiologist. He immediately said they were both correct. He went on to explain that the effects of the moon on plants are well documented in countries near the equator where the moon orbits closest to the earth. The effect is less pronounced at higher northern or southern latitudes farther away from the moon's orbit. The moon orbits the earth in an 18-year cycle on either side of the equator between 10 degrees of north and south latitude. The moon and sun's gravitational pull causes tides in the ocean and also in the earth's biosphere which is also almost entirely composed of water.