Gardening by the Moon

"Plant by the Moon" sounds like one rule. It is really three separate systems that grew up at different times, use different parts of the sky, and quite often give different answers for the same day. Most confusion about lunar gardening comes from mixing them up.

This lesson takes them one at a time, then shows how they combine and where they disagree. It builds on The Moon in the almanac.

As always: this is a tradition, offered as history and as an interesting way to plan a garden. Weather, soil, season and the instructions on the seed packet matter far more than any day in a calendar. The stars incline; your tomatoes still need water.

System one: the phase

The oldest and simplest system looks only at the Moon's phase — how much of her is lit. It goes back at least to Roman farming writers, and it rests on one idea: as the Moon grows in light, things above ground grow; as she shrinks, the strength goes down into the roots.

American almanacs split it into four quarters, and this is the version most people meet:

Some gardeners simplify it further to "sow above-ground crops on the waxing Moon, root crops on the waning Moon", and many avoid sowing on the exact day of the New or Full Moon.

System two: the sign

The second system looks at the zodiac sign the Moon is in — the ordinary tropical sign, the one in any ephemeris. It comes from traditional astrology's division of the signs into fruitful and barren.

• Fruitful: the water signs, Cancer, Scorpio and Pisces. The best days for sowing, planting, grafting and watering.
• Semi-fruitful: Taurus, Capricorn and Libra. Good for sowing, Taurus and Capricorn especially for root crops and anything meant to last.
• Barren: Aries, Gemini, Leo, Virgo, Sagittarius and Aquarius. Not for sowing — kept for weeding, mowing, clearing ground, pest control and harvesting crops that should come in dry and keep.

William Ramesey, writing in 1653, gives the flavour. For trees and plants that should be long-lived he wants the Moon in Taurus or another fixed sign; for sowing seed, the Moon increasing in Cancer or Capricorn; and he allows that peas, oddly, do better sown on a waning Moon. Modern almanacs have kept the fruitful–barren division almost unchanged.

System three: the biodynamic calendar

The third system is the youngest and the most different. It was developed by the German gardener Maria Thun from the 1950s onwards, within the biodynamic movement that followed Rudolf Steiner's agriculture lectures of 1924, and her family still publishes it every year.

It assigns every day to one part of the plant, by the element of the star group the Moon is passing in front of:

Two things make it unlike the other systems.

It uses the constellations, not the signs. The biodynamic calendar follows the real star groups along the ecliptic, which are of very unequal size — Virgo stretches over forty degrees, while the Moon crosses Scorpius proper in well under a day. And because the equinox has drifted backwards against the stars over two thousand years, the constellations now sit almost a whole sign behind the tropical signs of the same name. This is a sidereal system: it follows the stars, not the seasons.

It adds the ascending and descending Moon. This has nothing to do with waxing and waning. Over about 27 days the Moon's path across the sky climbs higher each day, then sinks lower. While she climbs, sap is said to rise, and it is a time for sowing and taking cuttings; while she sinks — "planting time" in Thun's calendar — it is the time for transplanting, pruning and spreading compost.

The calendars also mark short unfavourable spells, around the Moon's nodes, perigee and eclipses, when nothing should be sown.

How they combine — and where they disagree

On a good day the three systems agree, and almanacs love those days. A waxing first-quarter Moon in the last degrees of tropical Cancer, just arrived in front of the stars of Cancer, is a day for leafy crops by phase, a fruitful water sign, and a leaf day: lettuce, three times over. Because the constellations sit almost a sign behind, such days are rarer than you might expect.

But because the systems count the sky differently, they often don't agree, and sometimes they flatly contradict each other. Take a waxing first-quarter Moon at 10° Gemini on the tropical zodiac:

• By phase: first quarter, so sow leafy crops.
• By sign: Gemini is barren, so don't sow anything — weed instead.
• Biodynamic: at 10° tropical Gemini the Moon is in front of the stars of Taurus, so it is a root day.

Three systems, three different answers. None of them is "wrong" by its own rules — they are simply different traditions.

Gardeners who follow the Moon tend to choose one of three approaches:

1. Pick one system and stick to it. The simplest, and the most common. Phase gardeners and biodynamic gardeners usually work this way.
2. Use the phase for timing and the sign for the task. The traditional almanac approach: the phase says whether to sow at all, the sign says which kind of crop, and a barren sign overrides both for sowing.
3. Look for agreement. Save the most important sowings for days when the systems line up, and treat the rest as ordinary days.

What you should never do is mix a tropical sign with the biodynamic table — reading "the Moon is in Gemini, so it's a flower day" — because the biodynamic calendar is not using Gemini the sign at all.

What the evidence says

The trials have not settled it either way. Thun reported clear differences from her own decades of trials. A long, careful study by Hartmut Spiess in 1990 could not find the constellation effect; a 2001 review by Nick Kollerstrom and Gerhard Staudenmaier argued for it on a re-analysis. The phase and sign systems have had even less formal testing. Many gardeners who follow it are sure of the difference in their own beds, and the fairest test is yours: keep notes for a season or two and compare. Weather, soil and season still come first.

Whatever you conclude, lunar gardening gives the month a shape. It takes you outside, has you look at the sky, and tells you the next job.

In the Almanac

The Moon section of the Almanac keeps the three systems apart, each in its own tick box:

• Gardening by phase shows the quarter and the jobs given to it.
• Gardening by sign shows whether the Moon's sign is fruitful, semi-fruitful or barren, and what it suits.
• Biodynamic days shows the root, leaf, flower or fruit day, worked out from the Moon's constellation — not her tropical sign — and whether she is ascending or descending.

Tick one, two or all three. When they disagree, the panel shows each answer side by side and doesn't pretend they are the same thing.

One last thought

The three systems are a good reminder of something true about astrology in general: there is rarely one "correct" reading of the sky, only traditions with their own logic. Choose the one that makes sense to you, notice what happens in your own garden, and let the Moon be a companion rather than a rulebook.