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The Garden Scoop

Our Moon and the Old Farmer's Almanac

This weekend, I will be traveling to southern Illinois for the experience of a lifetime—a total solar eclipse.  The eclipse will occur on Monday, August 21, and will only be viewable in “totality” within a narrow band of approximately 70 miles that extends across the US from Oregon to South Carolina.  Unfortunately, in our area we will only be able to view a partial eclipse, which is still fascinating, but does not carry the life-changing impact that many experience from a total eclipse.

As I was preparing to view the eclipse, I began to consider the potential impact the eclipse may have on plants.  Is there anything observable I should watch for?  Although the eclipse occurs over several hours, total darkness only occurs for a matter of minutes. It was interesting to see that some folks around the globe have researched plant and animal response during an eclipse.  Overall, it appears there is no major impact to plants.  Although some studies did find a measurable reduction in photosynthesis, it would be negligible in overall plant production and will not result in recognizable impacts.

While the eclipse will have little effect on our plants, when I was considering the impact of celestial events on plants, one interesting bit of folklore and tradition came to mind: The Old Farmer’s Almanac. It has been providing readers with farming recommendations since 1792.  The annual publication, which is one of the longest running periodicals in North America, has provided readers with advice on everything from when to plant or harvest crops, to long-term weather forecasting, to other predictions on social trends.  With its quirky ads and wide ranging subject matter, there is usually something for everyone.

I don’t want to present The Old Farmer’s Almanac as scientifically proven methodologies for crop production, as it certainly is not.  However, many farmers over past centuries have followed it closely when planting crops, and some refer to it as “planting by the signs.”  To me, it is an interesting part of our agrarian history in the US and provides a window into past understanding of the natural world. 

The planting and harvesting recommendations in The Old Farmer’s Almanac are based on the premise that the moon impacts water on earth, which we can see from tidal influences, and cycles of the moon will impact plant growth.  Therefore, planting and harvesting recommendations were based on the phase of the moon and the specific sign of the Zodiac for that particular day, thus the term “planting by the signs.” 

For example, one general rule is to plant annual flowers and vegetables that bear crops above ground during the waxing moon and to plant flowering bulbs and vegetables that bear crops below ground during the waning moon.  Signs such as Scorpio, Pisces, Taurus or Cancer are considered fruitful, and it is recommended to plant during those signs.  Other signs, such as Taurus and Cancer are attributed to more drought tolerance when planted at those times.

The Old Farmer’s Almanac also provides regional long-term weather forecasting, which is a tricky business.  According to the book’s website, “We derive our weather forecast from a secret formula that was devised by the founder of this almanac, Robert B. Thomas, in 1792.”  The original formula is kept in a black box that is locked, and few in history have observed it, adding to the mystic.  Thomas’ formula is noted to be based on the belief that sunspots influence weather on earth.  The website also notes that, “We have refined and enhanced the formula with state-of-the-art technology and modern scientific calculations.”  Over the years, the Almanac’s predictions have been criticized for being blatantly wrong and sometimes have been eerily correct. 

One professor emeritus at University of Illinois did take a scientific look at the accuracy of The Old Farmer’s Almanac.  John Walsh, in the Department of Atmospheric Sciences, conducted a study testing the accuracy of the almanac’s monthly temperatures and precipitation forecasts by comparing them to the actual weather data over a 5 year period.  Results of this study found that 51.9% of the monthly precipitation forecasts and 50.7% of the monthly temperature forecasts were accurate, concluding that these percentages are similar to the 50% success rate expected by chance. 

Overall, The Old Farmer’s Almanac is a very remarkable piece of US history and, beyond planting recommendations or weather forecasting, each addition does include a number of interesting, factual articles for gardeners and others.  It truly does have something for everyone and I encourage interested readers to pick up a copy.  I’ll leave it up to you as to whether or not you plan your crops around it!


More information on The Old Farmer’s Almanac is accessible at:

Dr. John Walsh’s research is accessible at: