It's seedhead time...

Casey Sheehan
Assistant GC Superintendent

As we get into another golfing season, a common question that we often hear early in the season is “why are the greens so bumpy in the spring?” This bumpiness is due to the high population of poa annua or annual bluegrass in the putting greens.  Since the annual bluegrass is an annual plant it produces seeds in the spring, even at the low mowing heights of a putting green.  As a result, these seedheads produce a bumpy and untrue putting surface.



Poa annua seedheads



In an effort to minimize the number of seedheads that the poa annua population produces, two spray applications are made in early spring.  These applications are a combination of two plant growth regulators (PGR), which over the last few years have shown to be somewhat successful in controlling the emergence of seedheads.

Since every annual bluegrass plant will not produce seeds at the exact same time the goal of these applications is to try and reduce the number of seedheads that emerge.  Therefore, when to make these applications is the most important and most difficult factor to determine in achieving a sufficient amount of control in seedhead production. 

Here at Huntsville Golf Club we base the timing of these applications on two points.  One is the visual observation of annual bluegrass seedheads in fairways and rough.  Since the grasses in these areas are mowed at a higher mowing height the seedheads emerge sooner.  The second basis for the timing of these applications is on a growing degree day model.  The model uses a mathematical equation to determine the optimal application time using a day’s average temperature and dividing that by 32.  For example if a day’s high and low are 57˚F and 33˚F, the
average is 45˚F divide that by 32 and we get a growing degree day of 1.4.  There can be no negative numbers in the model so if a day is calculated to have, for example, -1.4 the day is given a 0 for a growing degree day.  We usually start counting growing degree days in early march and we will get a growing degree day every day until we start approaching 300 growing degree days.  The latest research out of universities is to have the first application on the greens as close to 300 growing degree days as possible.  We then follow up the first application with a second, two weeks later to try and control any stragglers. 

"...seedheads produce a bumpy and untrue putting surface."

Obviously both of these techniques will not guarantee 100% control, but as it was stated before, the goal of these applications is to minimize the effects of seedheads to ball roll.  The good news is that the flush of seedheads that the annual bluegrass population produces is only temporary. As we move into the summer months the seedhead production will greatly decrease and the greens should become smoother and true.

Article written by Casey Sheehan, Assistant Golf Course Superintendent