How to Choose a Moon Planting Guide

Photo by Mike Cattell

I have done my planting by the moon signs as much as I can in the last 2-3 years, and hope to be better about it this year as I learn more. I have had some success, but my gardening has also been hit or miss because I didn't understand at first that there are TWO different methods of determining the moon signs. No wonder so many of us are confused and have unreliable or conflicting results!

One method is geocentric... that is, looking at the signs as if the earth is the center of the universe. (The Gardening by the Moon Calendar is based on the geocentric and astrological calculations.) When the Moon's position is computed geocentrically, it's computed from the center of the Earth. For planting, this is entirely correct and logical. We live on the Earth; we plant on the Earth. All our activities are "Earth-centered."

When a computation is made to find the Moon's location in the heavens as an astronomer does, it is computed from the center of the Sun, or heliocentrically. (The Old Farmer's Almanac is heliocentrically calculated.) This system is more complicated and also takes into consideration eclipses, trines, apogees and perigees as well as descending and ascending moons.

To clarify... If you compared a geocentrically calculated almanac with one calculated heliocentrically, you'd find that on the first day of January 1985, a geocentric calendar would show the Moon in Taurus, and a heliocentrically calculated one would show the Moon in Aries. This difference is a vital when planting.

Fortunately most calendars showing the Moon's signs are geocentric, as are most (but not all) almanacs. If you choose to plant by a heliocentric calendar (like the Old Farmer's Almanac) you will have very different results than if you plant by a geocentric calendar (like the Gardening by the Moon Calendar).

Update: Yes, The Old Farmer's Almanac is heliocentric. However I understand that their separate page of Planting by the Moon Signs is geocentric. It does not show the time of day the moon enters a sign but it is still usable as a general planting guide.