Does the Moon Affect Plants? Part 3: Gravitational Effects?

moon_tree.jpgDoes the Moon’s Gravity Affect Trees?

To me this sounds like a silly question.


Because I’d no more expect the moon’s gravity to affect trees than it affects the water in a pond or swimming pool.

If the moon doesn’t elicit tidal effects in such small bodies of water, then why would its gravity affect trees?

But, largely due to so-called “peasant beliefs” passed down through the ages, there are some who are convinced that the moon’s gravity does indeed have measurable effects on trees.

Do the Tides Correlate with Tree Rhythms?

In 1998, Ernst Zurcher and colleagues published this paper in the scientific journal Nature claiming that they had evidence that there was a correlation of tree stem diameters and the tides.

This, and other lunar effects on trees, was discussed by Zurcher in a subsequent publication (see ref. 1 below).

In 2000, a another team of scientists provided evidence against Zurcher’s conclusions (see ref. 2 below).

You Decide

Sequoia.jpgFrom the physics of gravity explained by a fellow by the name of Isaac Newton, it seems obvious that the moon’s gravity is too weak, the distance from Earth to moon too large, and even a giant Sequoia’s mass is too small for the moon to have any significant gravitational effect on trees.

But the notion simply won’t die.

So you, dear reader, weigh the evidence – even do the calculation – and be the judge.

1. Zurcher, E. (1999) “Lunar Rhythms In Forestry Traditions – Lunar-Correlated Phenomena In Tree Biology And Wood Properties .” Earth, Moon, and Planets vol. 85-86, pp. 463-478. (PDF)

2. Vesala, T., et al. (2000) “Do tree rings shrink and swell with the tides?” Tree Physiology vol. 20, pp. 633-635. (PDF)

Bottom Line: Despite what we know about the laws of gravity and even direct scientific evidence to the contrary, some still believe that the moon affects trees as it does the tides. Oh well. Sigh.

Dark Side of the Moon – “…Brain Damage/Eclipse” by Pink Floyd

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  1. Dear Editors,

    Thank you for dealing with this interesting subject.

    Concerning “Tides in Trees” let me please inform you that a recent extensive study could bring a very convincing proof of the phenomenon:

    Barlow, P, Mikulecky, M. and Strestik, J. (2010): Tree-stem diameter fluctuates with the lunar tides and perhaps with geomagnetic activity. Protoplasma online, 15.April 2010 (19 p).

    Yours faithfully

    E. Zürcher

    Ernst Zürcher,, Forest Engineer ETHZ
    Professor for Wood Science / Research
    Wood Division

    Bern University of Applied Sciences BFH
    Architecture, Wood and Civil Engineering AHB
    Burgdorf, Biel

    Solothurnstrasse 102
    CH-2500 Biel 6

    Phone: +41 (0)32 344 03 67
    Fax: +41 (0)32 344 0390

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