Friday, December 22, 2017

The Shortest Day of the Year .... and Why it Matters

Today, December 21, is the winter solstice and that means it’s the shortest day of the year for those living in the northern hemisphere. Technically speaking, the winter solstice is when the sun is directly over the Tropic of Capricorn, or 23.5 south latitude. Non-technically speaking, it's the day when the sun rises and sets to our south at the lowest angle, and it marks the first day of winter.

Because the earth orbits around the sun on a tilted axis, between September and March the entire northern hemisphere gets less exposure to sunlight. Because of our location, it’s not a coincidence that these months coincide with the seasonal influx of residents to Southwest Florida and the play at Olde Florida Golf Club is at its peak.

In basic terms, for turfgrass to thrive it needs sunlight, the correct amount of water, adequate fertilizer and a good soil structure. Of these needs, the one that is least in our control is sunlight, which 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. That means it grows 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 do everything in our control to maintain plant health for the next 60 days. By March 1, 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.

Hole 9 (pictured above) is the southernmost hole at Olde Florida Golf Club. The hole plays from east to west, so the sun rises to the southeast of  the tee and it sets to the southwest of the green.  On the day after the winter solstice, the angle of the sun will continue to shift slowly to the north until the sun rises to the east of the back 9 holes at Olde Florida.