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Predicting the End of Maple Sugaring Season – Caveat emptor

Back to the Growing Degree Days (GDD) calculation, and “knowing” that Sugar Maples budbreak between 30-50 GDD°C base 10 (54-100 GDD°F base 50), how then does that help us?  Even predicting the end of the season is of dubious value I suppose, but it seems like a good exercise.  So, I’m just taking a relatively uninformed shot at this prediction; I have not tested the results against “real life” as recorded in prior years, nor have I used records from real life in prior years to inform this prediction.  In other words, caveat emptor.

Below is a chart showing in the blue columns, against the left hand y-axis, growing degree days as they have been witnessed so far this year.  We started to see some growing degree days accumulate in the last week of February, prior to that 1 had been chalked up on Jan 21st.  We have accumulated year-to-date, that’s the bold orange line near the bottom of the chart, against the right-hand, and second y-axis, somewhere between 15 and 20 GDD°F base 50, the actual number is 16.  Remember, we need at least 54 to get to Sugar Maple budbreak, and the end of sugaring season.  The thin orange line, also against the right-hand axis, is a best-fit exponential curve predicting the future accumulation of growing degree days based on our history so far this year.

Now, there are few things that behave as straight lines in nature, so I chose not to have the spreadsheet fit a straight line to the data.  And, an exponential curve kindasorta looks like how I expect things will develop in the near future, so I had the spreadsheet perform that fit.  Call it another experiment.  We’ll see how reality stacks up against this curve as we continue into spring.

Again though, the experts say that budbreak for a Sugar Maple will occur between 54-100 GDD°F base 50, but what I want to know is when that will happen on the calendar! So, with the brute force offered by modern-day spreadsheet tools, we are simply able to start at Jan 1 and solve the best fit equation (see the equation below) going out as far as we would like. That is exactly what I did, and, voila, spreadsheet SAYS!

Brute Force calculation of predicted Sugar Maple budbreak

The spreadsheet says day 54 will come Mar 26th or 27th, and the 100th GDD°F base 50 will come between Apr 5 and Apr 6.  In other words, my prediction is  that we have  somewhere between 12 and 23 days left in the season.  The next 10 days look pretty favorable (see image below), a great deal of temperature fluctuation around freezing, and, no additional growing degree days, so my money is on the start of this range of dates being in the right place on the calendar.  The back end of the range, well, time will tell.  If nothing else, we’ll learn something “new,” or at least something new to me.

All the best,


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