The Winter Solstice

Today is December 21... and all golf course superintendents in the south are keenly aware of the importance of this day. It means the winter solstice has arrived! This is a key date for those of us living in the northern hemisphere because it marks the shortest day of the year. 

The winter solstice is when the sun is directly over the Tropic of Capricorn, or 23.5 south latitude, which is the day when the sun rises and sets to our south at the lowest angle. Because the earth orbits around the sun on a tilted axis, between September and March the entire northern hemisphere gets less exposure to sunlight. It’s also not surprising that these months coincide with the seasonal influx of residents to Southwest Florida, and golf play is at its peak. 

So why is this important to a golf course superintendent? In basic terms, for turfgrass to thrive it needs sunlight, water, air and nutrients. Of these needs, the one that is least in a golf course superintendents control is sunlight. This is why an understanding of the earths rotation and the winter solstice is vital. Also influenced by the angle of the sun are air and soil temperature. Bermudagrass, the turfgrass that comprises the playing surfaces at Olde Florida, is a warm season turfgrass. Warm season grasses grow best when the average daily temperatures are above  75°F.  In addition, soil temperature, as influenced by air temperature is also important to the growth of bermudagrass. Soil temperatures above 65°F are required for significant growth, and the optimum soil temperature for root growth is around 80°F. 

Since the duration and intensity of the sun's rays (and air and soil temperature) is out of our control, it is extremely important to have plant health peaking on this day and then do everything in our control to maintain plant health for the next 60 days or so. By March, the nighttime temperatures have increased, the sun is high enough in the sky and  the days are long enough that sunlight essentially becomes a non-factor.

December 2022

Holes 8 and 9 are the southernmost holes at Olde Florida. Both play from east to west, so on December 21 the sun rises to the southeast of  8 and 9 tee and it sets to the southwest of  9 green.  

Tomorrow, the day AFTER the winter solstice, the sunrise and the angle of the sun will slowly begin to shift to the north. This will bring a little more sunlight to our turfgrass each day!