Little scientific research exists on gardening according to the lunar calendar. Folklore associates the phases of the moon with gardening activities based on the moon's gravitational pull on water. Some modern practitioners of lunar gardening believe that the moon's position with reference to the zodiac is also important.
The new moon is one of the two points in the lunar cycle when the gravitational pull of the moon on water is strongest. Lunar gardeners believe that the new moon pulls moisture up in the soil, creating favorable conditions for germination. Folklore states that the new moon is the time to plant above-ground plants that produce external seeds, such as lettuce, broccoli, celery, cauliflower and spinach.
Lunar gardeners point to the moon's second quarter as favorable for leaf growth because of increasing moonlight. The best plants to sow at this time are those that produce their seeds inside fruit, including tomatoes, peppers, squash and beans. The full moon provides maximum moonlight and has a similar effect to the new moon on soil moisture. Lunar gardeners plant root crops by the full moon, including carrots, beets, onions, radishes and beets. Folklore considers the fourth quarter of the moon unfavorable for planting.
Scientists have mixed opinions regarding lunar gardening. Some believe any beneficial effects are due to meteorological cycles influenced by the moon. Others believe that lunar gardening may succeed simply because the gardeners are paying more attention to their gardens.