Plant Preview

Welcome to Plant Preview, a blog dedicated to helping gardeners learn about gardening techniques and preview new plant cultivars. Read about new plants here first and hear how your "comrades in compost" are making use of new plant introductions in their gardens and landscapes. Blog author Geri Laufer is a life-long dirt gardener, degreed horticulturist, author and former County Extension Agent. Plant Preview is copyrighted by Geri Laufer.

Monday, December 20, 2010

Winter Solstice, Full Moon, Lunar Eclipse and Plant Photoperiodism

And now for something completely different due to the season of the year! I am fascinated by the heavens. As the days grow shorter and shorter and winter approaches, astronomers tell us the Winter Solstice arrives at 6:38 EST on Dec. 21, 2010. This is the shortest day and the longest night of the year.

In the early evening the maximum tilt or declination of the North Pole away from the Sun (its axis is 23.7 degrees away from the vertical) will begin to reverse itself as the Earth begins to shift on its axis, and as the planet "straightens up" the days in the Northern Hemisphere will begin to grow longer in anticipation of summer. 

December 21 is the turning point when the days begin getting longer again, so it has been celebrated as the ‘return of light’ since the Stone Age. The famous site known as Stonehenge in England has standing stones arranged to pin point the last rays of sunshine at sunset on the Winter Solstice, an event that was seen as the reversal of the sun’s ebbing presence in the sky and the rebirth of the year.  Originally, the burning of the Yule log was significant during the Winter Solstice, representing the return of the light, and eventually becoming a well-loved Christmas tradition.

Living organisms are affected by the day’s length. During those short winter days, people can experience SAD or Seasonal Affective Disorder, also known as the winter blues, which is treatable with bright light therapy and other strategies.

Plants respond to day length in more direct ways. Photoperiodism is the term used to discuss plant responses to day length or more accurately, night length.  “Short day plants” flower as the days grow shorter during late summer and fall (a couple of examples are goldenrod and chrysanthemum). Well-known as a Christmas flower, the poinsettia develops its showy bracts as the year approaches the Solstice, while the day length is decreasing and there are a long, unbroken periods of darkness each night.

Other plants (like clover, foxgloves and garden pinks) are called “long day plants” because they bloom as the days get longer and the nights are short. Still others are “day neutral  plants” because they are less responsive to the length of the daylight period. Spring and Fall Equinoxes are the midway point of the solar year.

This year in addition to the Winter Solstice, two other celestial events will occur on December 21: a Full Moon and a Lunar Eclipse! The Moon’s orbit will take it to the far side of the Earth, positioning Planet Earth between the Sun and the Moon, and causing the Earth’s shadow or umbra to fall on the face of the full moon and turning it a dark copper or brown color for a few hours.

According to NASA, here’s a Time Table for these occurrences:  

Early morning Dec 21 1:33 am EST         Full Moon begins to enter Earth’s shadow
Early morning Dec 21 2:41 am EST         Moon will be completely eclipsed
Early morning Dec 21 3:53 am EST         Moon begins to come out of the Earth’s umbra
Early morning Dec 21 5:01 am EST         Moon is fully visible
Morning Dec 21 7:34 AM EST                   Moonset/ Daylight
Early Evening Dec 21 5:25 PM EST         Moonrise-- Full Moon  
Late night December 21 6:38 pm EST     Winter Solstice; Earth begins to change the tilt on its axis, moving the northern hemisphere toward the Sun  

Dear Readers, All good wishes of the season from gardengeri

photo credits: Stonehenge:; moon during eclipse:  Thank you


  1. Thanks for the info friend! All good wishes to you as well

  2. So nice to find that you are reading the Blog. Best wishes for a Happy New Year!