Gardening by the Moon?

by Carol Barany, Master Gardener

Just in case you need something to do, the moon is in a Waxing Gibbous phase today, 73% illuminated, and in the sign of Sagittarius. According to traditional lunar planting guides, it’s a great day for planting above-ground crops.  You could also go out and mow the lawn, kill some plant pests, catch up on your weeding, and dig some holes. Just don’t plant any root crops.  

Gardening by the moon is an ancient practice originating thousands of years ago in early agricultural civilizations in Mesopotamia, Egypt, and ancient Rome. Early farmers used lunar cycles for more than timekeeping. They believed the moon’s gravitational pull influenced the movement of soil moisture and sap much like it influenced ocean tides.    

During a Waxing Moon, it was thought that lunar gravitational pull brings moisture up to the soil surface and into plant tissues. That tradition says this is the time to plant above-ground crops and leafy greens. The theory suggests that seeds absorb the most water during the New and Full Moon phases, when gravitational forces are strongest making these dates especially favorable for germination.  

During a Waning Moon the pull decreases and moisture slowly recedes downward. Tradition says to plant root crops, weed, and prune.

Gardening by the moon is not only an ancient concept but remains a fundamental part of the Farmers’ Almanac philosophy.For over 200 years, the Farmers’ Almanac has published an annual Planting Calendar that uses phases and the position of the Moon to predict the best times for planting crops and performing specific gardening tasks.

Readers of the Almanac have long sworn by this method. 

We know that the moon impacts the tides because of the gravitational force it applies to earth across the lunar cycle.  This relationship has scientific support and has been accepted as a principal of basic physics.

What about the beliefs and traditions surrounding the lunar influence on plant life?

In a 2022 publication, University of Illinois Extension cited a 2020 paper in the journal Agronomy titled, “What Has Been Taught and Thought on the Lunar Influence on Plants in Agriculture?’ 

In that paper, researchers reviewed over 120 scientifically supported references to assess whether or not the moon’s influence on earth extends beyond tidal movements to significantly effect the lifecycle of plants.

The moon’s gravity as it influences earth is approximately 300,000 times less than the effect of the earth’s own gravity. It was concluded that this influence is so negligible that it cannot have significant influence on plant physiology. 

The moon’s gravity and its affect on other factors in plant life, such as the force required for the capillary action that moves sap upward in plants, has also been determined.  In the case of capillarity, the force of the moon’s gravity was concluded to be completely imperceptible when compared to the force required to move sap up plant stems.

Researchers also looked at other aspects of the moon’s influence on plants, such as the light it reflects from the sun.  This lunar illuminance during a full moon was found to be 128,000 times less than sunlight provides and was not found to be significant in photosynthesis or plant lifecycles.

Based on their review and the factors we know about the moon’s influence on earth, the authors of the Agronomy paper found that there was no reliable science-based evidence for any relationship between lunar phases and plant physiology in any plant-science related textbooks or peer-reviewed journal articles that could justify agricultural practices conditioned by the Moon. 

The University of Illinois publication did mention some interesting relationships discovered in the Agronomy review.  In one case, a Middle Eastern shrub was found to produce more pollen under a full moon which correlated with higher pollination success since it attracted pollinators better able to navigate by full moonlight. 

The authors of the Agronomy study concluded that additional research is needed, especially in light of the widespread global traditions surrounding perceived lunar-plant relationships.  While additional research may uncover new and interesting aspects, it also serves to promote critical thinking and use of the scientific process over simply following tradition.

Farmers’ Almanac readers have long sworn by gardening by the moon as a method of managing their gardens and crops.  However, the Farmers’ Almanac authors also ask that readers consider their regional weather and climate before following the suggestions they make in their planting guides. The Farmers’ Almanac uses broad formulas that do not match every microclimate.  Local soil temperature and frost dates matter more than calendar days. 

They also recommend that gardeners talk with their local agricultural extension office for specific gardening guidance.