Labor Day

Happy Labor Day. This holiday can sometimes signify the end of summer and the beginning of fall or it may just be a bump in the road as summer rolls along. Whichever it is, a few things do change for sure when the calendar turns to September (including the start of another football season!).

One change noticed by everyone is that day-lengths begin to shorten dramatically as we move into September. Sunrises move later and sunsets move earlier. With this change at both ends of the day we typically lose 1 to 2 minutes of daylight per day. For most, this is an unwelcome change because outdoor activities that used to stretch well into the evening are now squeezed into shorter days. For turf grass though, it is significant because the daytime is when the turf grass is subjected to stress. The sun gets a later start in drying the grass out and finishes earlier in the evening. This translates to the window of stress on the turf being smaller. Less stressed time means that we can push the turf harder and can expect better tolerance and recovery.

Another change that occurs is that the angle of the sun begins to change. With each passing day the sun gets lower in the sky and thus the intensity of suns’ rays decreases. In the middle of summer, when the sun is directly overhead and beating down most intensely, the turf is under the most stress. Each passing day thereafter, the sun begins to shine on the turf at ever decreasing angles. The smaller angle diffuses the heat intensity that the rays can impart on the turf and the grass is much more capable of managing the warmth.

Finally, the overall average daytime and overnight temperatures begin to drop significantly in September as well. Many sources are available to check average temperatures but generally for August the average daytime high temperature is 85-87 degrees Fahrenheit. However, for September, the average drops to around 81-83 degrees Fahrenheit. Similarly, the overnight lows drop from 65-67 degrees down to 61-63 degrees. These both are significant changes. The daytime highs are somewhat clearer as to the importance of lower temperatures. Lower temperatures cause less direct heat stress and the turf grass is far more tolerant. Somewhat less well-known, is the importance of lower overnight temperatures. When the overnight temperatures drop below 70 degrees the level of disease pressure drops drastically. Also, as the overnights continue to drop down into the low 60’s, the turf grass can “catch its breath” overnight. The grass can recuperate from most stresses of the day more efficiently and effectively. Recovery overnight means that the grass is not still under stress from the previous day as it heads into the next day.

So as we all head in a little earlier because the summer-time sun is going down sooner, the turf is breathing a small sigh of relief as it recovers for tomorrow.
 

 

See you on the course!

Joe

jvillegas@bwrc.org