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Does Planting by the Moon Work?

The idea that the Moon affects plant growth is an old one that is believed by many people. It can be found in the folklore of ancient societies ranging from the Celts in Britain to the Maoris in New Zealand. Roman historian, Pliny the Elder, in his History of Nature, Book 18, gives much advice on planting by the moon phases. Today, it is still a rural tradition and in most countries you can buy moon gardening calendars.

The lunar experts suggest that you pick fruit at the full moon for the market as it will weigh more and pick at the new moon for personal consumption because the fruit stores better. Seeds also germinate faster when planted under the right phase of the moon.

A picture was posted recently in a Facebook Group showing a Planting by the Moon calendar on sale. I made a comment about being surprised people still believe in such things. That was a big mistake. Dozens of people castrated me for not being a believer. How dare I say anything derogatory about what granny believed. Not one person came to my defense. The belief in planting by moon phases is still very common.

Planting by the moon phases

Planting by the moon phases

Planting by the Moon – The Biological Clock

Mammals, including humans, have an internal timing mechanism called the biological clock which controls circadian rhythms on physiology, biochemistry and molecular events. We all know how screwed up our system gets when we fly across time zones.

It is a tiny leap of logic to think that plants, which are so dependent on light, also have such a system and in fact they do. But their system is external and controlled by the environment. It is incorrect to think that plants behave like animals. They don’t have an internal 24 hr clock like we do. Updated Dec 22, thanks to a comment by Chuck Chapman. It has now been shown that plants do have a internal circadian rhythm (ref 7).

The fact that they have a biological clock is not proof that changes in moon light have an effect on plants.

Planting by the Moon – Gravitational Pull

Issac Newton’s laws of gravity explains that tides exist because the water in the oceans is being pulled by the moon’s gravity. Both the moon and sun pull on earth but since the moon is so much closer it has a greater effect than the much larger sun. Our oceans are affected the most when the moon and sun pull from opposite sides of the earth, or when they pull from the same side, resulting in higher tides.

If the moon can pull water in the ocean to cause tides, surely it also affects the water in plants and in soil. It is claimed that at the new and full moon more water is pulled to the surface of the soil which has the effect of speeding up the germination process. I found this statement on line, “a lunar gardening calendar that combines the best moon phase and sign together will help you achieve optimum results”, and it comes as no surprise that the website that makes his claim also sells lunar calendars.

Let’s return back to earth and look at the facts. The moon definitely affects ocean tides and produces waves. It also affects everything else on earth, but, and it is a big but, the effect on most things is so small we can’t see it and in many cases can’t even measure it. We don’t see the tides on small lakes because wind and currents from incoming rivers have a much greater effect (ref 1) than gravity from the moon or sun. The Great Lakes, some of the largest on earth, haves tides that are at most 2 inches high.

I could find no scientific evidence that water levels are raised in soil during different phases of the moon nor is there evidence that the moon or sun affects the water level inside plants.

Claimed Research

A lot of the material on the internet refers to a 10 year study by Dr. Frank Brown, of Northwestern University. He found that in lab studies, plants absorbed more water during the full moon.

None of the dozen or more sites that refer to this work provided a reference. I have seen this before with other topics. People like to quote scientific studies to validate their belief without ever looking at the work. Dr. Brown did study the moon’s effect on animals, so the plant study may exist. If you find it, let me know.

Other legitimate scientific sites say that there has been no real research on the moon’s effect on plants.

Biodynamic Agriculture

“In Biodynamic agriculture the entire farm, the surrounding terrain, the influences of the waning and waxing moons, even the positions of the stars are all seen as integral to soil health and crop vitality. ” (ref 2)

They never went on to explain how the moon and stars affect soil health.

Different Moon Systems

Although many people believe in gardening by moon phases it is not common knowledge that there are actually three different belief systems.

Moon Phases

The more common one is based solely on the phases of the moon. Jackie French explains it well (ref 3), “Plant growth is supposed to follow the increase or decrease in the Moon’s light. So you plant crops or pick grapes during the waxing (increasing) phase, and harvest crops or cut timber during the waning phase. A refinement says you plant crops like peas whose yield is above ground during the waxing phase, and crops like carrots whose yield is below ground during the waning phase. Note how the refinement contradicts the original view. Other contradictory views exist. Thus one says you should sow seeds just before New Moon so the seeds will germinate and start growing in the waxing phase, while another more widespread view says you should sow seeds just before Full Moon. They can’t both be right.”

Moon Phases and Zodiac Signs

Since the moon passes through the signs of the zodiac it is only natural to conclude that they also affect plants. This belief is more fine tuned and takes both systems into account to decide the right time to plant and harvest.

Sidereal vs Tropical Moon Signs

In this system it is believed that sidereal moon signs are more important than tropical moon signs – whatever they are?

Which System is Right?

In my mind this is one of the big problems with this whole story. When you have three competing beliefs and even the believers can’t agree on which one is true, it really makes you wonder if any of them are valid. If one of these really worked, would someone not be able to show that it worked better than the other two?

Professor Stefan Buczacki, the former chairman of Gardeners’ Question Time on Radio 4 has been quoted as saying “It’s baloney,” he says. “If there was anything seriously in it, why over the centuries has not every gardener or, more importantly, every horticulturalist, followed these maxims? Why is it that people who plant by the moon don’t win all the prizes at the shows, or develop all the new varieties?”

Moon Light Affects Plants

There is scientific evidence that moon light does affect plants. The extra light can affect plants directly, and insects feeding on plants are also affected. But these effects don’t correlate with phases of the moon the way that is claimed by people gardening by the moon.

Lunar cycles do affect certain species, including some herbivorous insects which are dependent on moonlight for feeding.  During the full moon, such insects feed more heavily and affected plant populations retaliate by altering the digestibility of their tissues.

The only plants that use moon light for photosynthesis are certain types of phytoplankton which are not normally found in gardens. (ref 4)

Is Frost More Likely During a Full Moon?

Garden Myths - Book 1, by Robert Pavlis

Garden Myths – Book 1, by Robert Pavlis

This is a myth I believed for a long time. I discuss it more fully in my book Garden Myths but the bottom line is that there is no correlation between full moons and frost.

Full Moon and Lunacy

But surely it must be true that during a full moon people act more irrational, cause more murders and have more visits to hospital emergency rooms? No, that is not true either.

There is no support to the idea that the phases of the moon affects things like, births, heart attacks, deaths, suicides, violence, psychiatric hospital admissions and epileptic seizures. (ref 5).

Man has come up with many crazy theories about the moon and none are true, not even werewolves.

Rational  Thinking About the Full Moon

Non-believers plant according to calendar dates that reflect the last frost date. In my area the last frost date has always been around May 24. Global warming has thrown that out of whack, but I wanted to see how well the phases of the moon correlated with this date.

I got the date of the full moon that was closest to May 24, for each year between 2000 and 2020 (ref 6). The earliest was May 13 and the latest was June 9. That is a variation of almost 4 week. Even with the current erratic weather the last frost date does not vary that much.

Planting by the phases of the moon will surely get warm growing crops killed in some years.

What about other planting zones? Lets assume the phase of the moon is perfect for planting in my garden. Gardeners that are 2 zones warmer or 2 zones cooler will have the full moon on exactly the same day. Is it reasonable to think  that the weather and last frost date will be the same in all of these zones?

This is one of these myths that just does not make sense.

Why then do so many people believe in planting by the phases of the moon?

I used to believe that frost is more likely on a full moon, but as soon as I saw the data it was clear that my belief was wrong. I no longer believe it. Wouldn’t it be great if the world started believing in facts? Most disagreements and conflicts would end.

References:

  1. Why are there no tides in rivers and lakes, except oceans; https://www.theguardian.com/notesandqueries/query/0,,-199833,00.html
  2. Biodynamics; https://foodism.com/2017/05/09/biodynamics/
  3. Planting by the Moon; http://www.undeceivingourselves.org/S-plan.htm
  4. Moonlight Photosynthesis; https://www.thenakedscientists.com/articles/questions/moonlight-photosynthesis
  5. It’s Just a Phase: The Supermoon Won’t Drive You Mad: https://www.livescience.com/7899-moon-myths-truth-lunar-effects.html
  6. Full Moon Dates; http://home.hiwaay.net/~krcool/Astro/moon/fullmoon.htm
  7. Plant Circadian Rhythms: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1425852/

 

 

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Robert Pavlis
Editor of GardenMyths.com
I live in southern Ontario, Canada, zone 5 and have been gardening a long time. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

I hope you find Garden Myths an educational site that helps you understand your garden better.

19 Responses to 'Does Planting by the Moon Work?'

  1. Blythe says:

    What never made sense to me was the idea that at a certain point in time, the moon changes to waxing or waning, and so the advice of moon-phase gardening changes accordingly. However, I live by the ocean, and the tides are the most extreme a few days on either side of the full and new moons. It is never an abrupt change from one day to the next; it is a gradual influence that builds (or decreases) over time. It would seem that if we were to plant according to the greatest (or least) gravitational pull of the moon, we would plan our activities on either side of the moon phases. All the advice in the moon-phase calendars are just a few days off. So, I will stick to planting according to the NOAA forecasts and what has worked in my various microclimates, prune when I can get to it, and harvest when the stuff is ready. Thanks for another great post.

  2. pj772009 says:

    I saw that other Facebook post. I was about to come to your defense but that would have meant joining another group and who wants to hang out in places where misinformation is the flavour of the day.

    It’s surprising how rigorously people will defend old folk tales and refuse to consider science. I’m sure garden centers love those people if it means more sales.

  3. Andy P says:

    The light levels given off by the sun and moon are hugely different. For one thing, even though the moon looks bright, it still only reflects between 3 and 12% of the Sun’s light. Therefore if the moonlight had any effect it would be 90% down on what the sun can do.

    Also, with alternative theories, why do the effects of these things always have to be thought of as positive. Maybe, the effects of gravity, with full moons etc, have a negative effect on plants. The positive effects are certainly small, or non-existent, but perhaps the real effect, if it exists, is actually negative.

    Moonlight has less blue in it’s spectrum, and more red compared to direct sun light . So, even the light is of a different make up.

    Plants will have developed to deal with direct sunlight, since it is far more prevalent. Plants in general don’t want green light (or not much) since they reflect it, and the want blue and red light. Upset this balance and you would expect a negative effect.

    To detect water level differences in plants and soil due to the moon I would think that you have to control the air pressure and temperature in a very controlled way in order to see the gravitational effect of the moon. I would also think that this would be easy to achieve in a lab – how ever, probably not worth while because outside of the lab you can’t control these two things. Air pressure and temperature have such a huge effect on water any gravitational effect of the moon must be tiny on a tiny body of water.

    You can physically see the effects of temperature on water in a kitchen, just pour boiling water in a flask….then watch it shrink as it cools within seconds. You can never see the effect of the moon on a glass of water.

    The effects of air pressure on water can be seen in your toilet on a windy day. The air pressure in the drains alters with the wind gusts and you can see the water in the bowl go up and down.

    Moon phases can’t have much of an effect, and even if they did, the effect would be happening all the time as the phase changed hour by hour and day by day. No one day would stand out from the day before, or the day after.

  4. Rae Wade says:

    Robert: Another well-researched analysis that debunks a gardening myth. Keep up the good work. Rae Wade, Georgia Master Gardener

  5. Ram Gopal says:

    Similar to this is vedice farming as explained by Swamis Omkar.
    Giving the link below.
    Please read it by translating from Tamil to English.
    http://vediceye.blogspot.in/search/label/வேளாண்மை

  6. claire pare says:

    I think you may have been castigated by many people rather than castrated!
    Claire in Melbourne Australia

  7. Paul Alaback says:

    Glad to see you took on this common myth. I have also met people that say “its scientifically proven”, yet like you when I tried to find the proof all I found were many articles showing that it has no basis in fact, and certainly it does make any sense from a plant physics point of view, especially in terms of water transport.

  8. J Williams says:

    Wow! Evidence based gardening. Who knew? The best rational, scientifically based gardening site I have been able to find on the net.

  9. marianwhit says:

    Castrated you? Really? Wow, strong words…chastised maybe? I can’t imagine anyone succeeding in doing this to you. I like the method you use to correct your own errors…very scientific with a readable strike-through. We all make mistakes, and it may be that some day the romantics will be proven right, but until the evidence exists I will plant when I can find the time, lol. It takes a real man to own up to his errors, and that raises your credibility as scientist, teacher, and journalist in my book. Big cahones;)

  10. hff33725 says:

    facts? what are you, some hippy liberal? just kidding, politically speaking

  11. Planting by moon phases seems to be more romantic then scientific. But plants do have circadian rhythms, internal 24 hour clocks. The genes have been identified. They will follow these clocks when they have 24 hours of light, or dark. Not exactly 24 hours, as temperature affects the biological processes involved.

  12. Kate Russell says:

    Thank you for reminding us all to use our heads before taking those convenient leaps of faith. I categorize ‘lunar planting’ along with ‘companion planting’ – they both simplify gardening, in theory, but neither of them actually works.

  13. Even if the moon had some small affect on plants the weather during and for a few weeks after planting has a much larger affect on the success of that crop.

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