Home Page Science Frontiers

No. 118: Jul-Aug 1998

Issue Contents

Other pages

Other Interesting Sites











Lunacy In Trees

More than a half-century ago, Yale biologist H.S. Burr inserted electrodes into trees and found that the voltages between them varied with the phase of the moon. (Ref. 1)

The influence of the moon upon trees is even more palpable: the diameters of tree stems also bloat and shrink with the position of the moon in the sky. There is a tide in the affairs of trees, it seems. If tides occur twice a day, so do the swellings and shrinkings of trees.

These tidal patterns are evident even when the trees are kept in darkness and at constant pressure and humidity. Even more surprising, chunks of tree stems that are sealed to prevent water from flowing in or out will still expand and contract according to the 24-hour, 49-minute lunar cycle as long as the cambium, the most active growing region, survives.

The dimensional changes are small -- only tenths of a millimeter, but even these seem too large, given the weakness of the moon's gravitational field here on earth. (Ref. 2 and 3)


1. Burr, H.S.; "Moon Madness," Yale Journal of Biology and Medicine, 19:249, 1944.
2. Zurcher, Ernst, and Cantiana, MariaGiulia; "Tree Stem Diameters Fluctuate with Tide," Nature, 392:665, 1998.)
3. Milius, S.; "Tree Trunks Swell in Synchrony with Tides," Science News, 153:245, 1998.)

Tree-stem diameter (Top) Tree-stem diameter. Ordinate scale marks are 0.04 millimeters apart. (Bottom) Todal force. Ordinate scale marks are 20 milligals apart.

From Science Frontiers #118, JUL-AUG 1998. 1998-2000 William R. Corliss

Science Frontiers Sourcebook Project Reviewed in:


  • "A sourcebook of unexplained phenomena is therefore a valuable addition to a collection of scientific literature. William R. Corliss has provided this in the past with his source books of scientific anomalies in several subjects, and now he has provided it for astronomy. He has done an excellent job of collecting and editing a large amount of material, taken in part from scientific journals and in part from scientific reporting in the popular or semi-scientific press." -- "The Mysterious Universe: A Handbook of Astronomical Anomalies", reviwed by Thomas Gold, Cornell University, in Icarus, vol.41, 1980

  • "An interesting, systematic presentation of unusual weather [..] This book is recommended for a general audience" --"Corliss, William R., Tornados, Dark Days, Anomalous Precipitation, and Related Weather Phenomena, Sourcebook Project, 1983.", revieweed in Choice, September 1983
  • "..the science is necessarily somewhat speculative, but Corliss's symthesis is based on reputable sources." -- "Corliss, William R. (Compiler). Lightning, Auroras, Nocturnal Lights, and Related Luminous Phenomena" reviwed by Joseph M. Moran, Univ. of Wisconsin in Science Books and Films, Sep/Oct 1983

  • "Before opening the book, I set certain standards that a volume which treads into dangerous grounds grounds like this must meet. The author scrupulously met, or even exceeded those standards. Each phenomenon is exhaustively documented, with references to scientific journals [..] and extensive quotations" -- "Book Review: The moon and planets: a catalog of astronomical anomalies", The Sourcebook Project, 1985., Corliss, W. R., Journal of the Royal Astronomical Society of Canada, Vol. 81, no. 1 (1987), p. 24., 02/1987