Growing Degree Day Model


Signs of spring are showing up with each passing week. Although it is the 3rd driest stretch of weather from February 22-April 22 since 1871, we still see some of the usual spring blossoms. The forsythia bloomed, and the spring bulbs, like daffodils and crocus, have flowered, which are good early indicators of the start of spring. Typically we will start to see weeds begin to flower shortly after that. Most people think of the usual ones, such as dandelion, clover, and thistle, which are definitely on the move right now. It is a great time to try to knock those weeds back on the home front if you have an issue with them.

In the turfgrass management world, we also recognize this same time for the beginning of seedhead production for Poa annua, the often discussed grass by TV commentators. It has a place in the golf world, producing great surfaces in suitable environments. Still, we gear our management practices towards bentgrass growth and discourage the encroachment of Poa annua, particularly on the green surfaces. 

The greens are still pretty much free from this plant except for a few collars. The crew diligently removes much of it at this time of year by hand picking out individual plants before they become clusters and eventually larger patches. We also discourage this weed as much as possible through lean fertility, diligent water management, and a consistent growth regulation program that is based on a Growing Degree Day Model. Timing is critical for us, so using models like this in conjunction with monitoring our clipping yield per green helps us match what we are seeing visually with what we can expect to happen over time that correlates to these data points. This is the balance of art and science that is often eluded to in our profession. Ultimately, all of these decision points and data collection are used to drive a program that results in the best end product we can produce, with smooth and consistent putting surfaces.