Lunar control? Or lunacy?

Yesterday one of my dear skeptical colleagues sent me a link to a new article on lunar influences on plants (you can find it here).  Briefly, the authors argue that scientific evidence supports the concept of a lunar cycle influence on plants.  Interspersed within the discussion are references to seasonal and daily plant cycles, along with legitimate references to these verifiable phenomena.  (Had these references to circadian and diurnal rhythms been left out, the literature citations would have been rather paltry.)  Plants depend on these daily and seasonal cues for a variety of physiological and behavioral activities; lunar cycles have little obvious relevance to plants.  Nevertheless, “planting by the moon” is a belief system that has existed since ancient times.

This article is a great example of how pseudoscience insinuates itself with legitimate science.  Many of the references used as evidence for lunar effects on plants are of nebulous quality as they haven’t been reviewed by the scientific community; these include self-published books or lectures.  Furthermore, for every article that claims a lunar effect, I can find another discounting it entirely.  That being said, there are some legitimate papers indirectly linking lunar cycles with plant biochemistry.  Coincidentally, the lead author of one of these articles is a close friend and colleague whose research credentials are impeccable.

Here’s where the fascinating and complex nature of species interactions helps explain conflicting data.  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. It’s likely that these biochemical changes have been erroneously attributed to direct lunar influence rather than herbivore defense.

To demonstrate direct lunar influence, one would need to study plants in an herbivore-free, controlled environment so that the only variable under consideration was lunar cycle.  Under such controlled conditions, would the same changes be noted over time if plants weren’t eaten by moon-managed insects?  Would you see changes if you modified the lunar cycle to make it longer or shorter (again without insects)?  Positive and repeated results would be necessary to establishing a role for lunar control.

As with so many other mystical explanations of natural phenomena, the real story is infinitely richer and more satisfying.

11 thoughts on “Lunar control? Or lunacy?”

  1. I couldn’t agree more.
    At a party only a few weeks ago a lady found out I was a horticulturist and began to go on ad infinitum about the ‘moon method,’ as she called it. She seemed to be under the impression that because I was a horticulturist I would agree with all the mysticism-laden detailing she gave of lunar planting. When I mentioned the diurnal cycle’s influence on plant responses she kind of went cross-eyed. She’d never heard of it before.
    She told me she’d paid $300 for a weekend course on lunar planting and that it had improved her vegetable garden yields immensely. I asked how she gardened before she did the course and she said she’d had many failures and planted irregularly. With the lunar method she was planting something at least once a week and seeing great results.
    When I suggested that the change in her planting frequency and the seasonal (she wasn’t planting only seasonal vegetables before) produce she was planting can easily account for her vegetables’ increase in growth and yield, she got quite stroppy!
    When I said to her that I would even go as far to say that the lunar method works, not for it’s espoused mysticism qualities but rather it’s seasonal recommendations and its methodical nature, she was still quite irate.
    There’s no pleasing some people!

  2. Any papers about these “..herbivorous insects which are dependent on moonlight for feeding”? They can’t see?

    Seems that the moon’s gravity could effect the uptake of water in plants, or at least water available to plants. While I like your article above, and appreciate the points you make, has research also been done to prove that the moon does NOT have an effect on plants? My point is, I doubt if there is only one answer to this question, and wouldn’t stop with near-sighted bugs.

    1. Paige, there have been several studies documenting lunar effects on insects, especially in tropical areas. When researchers study this and other scientific questions, if they don’t find evidence to support their hypothesis they have effectively disproved it (in science talk, this means “accepting the null hypothesis”). There very well could be some lunar effect on plants – but such an effect must be consistently demonstrated under controlled conditions. Until then, planting by the moon and other similar notions can’t be considered science-based practices.

    1. Jon, it’s an excellent question. I did run into this article back in 2007. It *is* a peer-reviewed journal. That being said, there are some serious concerns I had with the article. I’ve summarized some of them here:
      Page 167: Photoperiodic effects of moon (literature review) – all of these are old and/or obscure references. Nothing in current scientific literaure suggests this. In fact, plant scientists pretty much agree that moonlight does NOT have a photoperiodic effect on plants. It is not intense enough to disrupt plant perception of daylength. It would be bad for plants if it did, since daylength perception is the FIRST signal plants have of seaonsal change. Temperature is secondary.
      Page 168: Plot size varies, making it difficult if not impossible to compare treatments statistically. The article does not explain how this discrepancy is reconcilled.
      Page 171: All the significant effects are due to temperature effects; they have nothing to do with lunar rhythms.
      Page 174: “Due to lack of space, only selected results are presented here…” This is cherry picking the data – and a serious error on the part of the author.
      Page 175: “…no significant differences between planting dates for five years.”
      The author has established in this work that lunar rhythms are not significant. What the study does show is the complexity of plant growth, and the fact that temperature has a significant impact.
      Bottom line: no significance to data; therefore lunar rhythms have no impact to rye growth and yield.
      This leads me to another problem – quality of the peer review process in some journals. Here are some of the flaws:
      Authors allowed to choose referees
      Reviewing process not blind
      Reviewers not well versed in area of study
      Finally, it’s worth noting that no one has published anything similar to this study since the article came out over 20 years ago. Considering that the preponderance of the scientific evidence on the topic says that lunar cycles have no direct effect on plants, that’s where the state of the science currently lies.

    1. Not sure what you are looking for, Kevin. I linked to an article that supports an indirect effect of lunar phases (i.e. insect activity). There is no high quality, peer-reviewed, published work that supports a direct effect of lunar phase on plant physiology. I have a very long list of articles that I can send you if you wish to email me, but I’m not going to post them here.

  3. This is what I do not understand. I know that objects with a large mass produces gravity. OK, the moon is a large object and it has an effect on the earth and the tides. The only difference between a new moon and a full moon is that the sun is shinning on its surface relative to it’s position to the earth. The moon does not go away just because the sun rays are not hitting it, therefore I do not see how the gravitational pull on earth is affected by the phases of the moon lighting.

    1. Mike, I think what proponents would probably say is that it’s the relative positioning of the sun and moon. If you look up “spring and neap tides” on Wikipedia you can find a good discussion on the phenomenon. Anyway, you can have the gravitational forces of each working against each other or with each other depending on their relative positions.

  4. Hello, I´ve been looking for this kind of information for years… Thank you!

    I´ve always heard about lots of different moon effects on plants (specially on grafts, cutting trees for wood, etc.), but when I´ve tried to find a scientific answer, a probably true one, I always got nothing.

    Then, sometime ago, I found this article:

    “Influencia de la Luna en la Guadua – Fundeguadua” by Tito Morales Pinzon

    Here, they found some relation between sugars in bamboo and moon phases!!

    So, as you explain, maybe not direct, but in can and does exist some moon effect on plants, through predators or other non yet found ways. I´d like to understand much more on all this. Maybe behind some ideas of those “believers of the magic” we can find some reality.

    So, is it possible that loggers and plant growers methods evolved (by hitting the target and falling through hundreds of years) until the better way was found?

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