There are a number of factors which play into the efficacy of seed head control, one of the greatest being that all Poa is not the same. We often speak of Poa as if it's a single, uniform grass, however hundreds of unique biotypes of Poa have been identified, some of which are truly annual grasses, while others (despite the name Poa annua) are perennial in nature. Because of this, there is great variability in seed production from one Poa biotype to another.
The lack of uniform control from start to finish this spring is also weather-related. The cool temperatures for much of April and May likely gave Poa a wider window during which it could produce seeds--basically, the Poa waited out the impact of our control sprays made in March and April. The timing of these applications is based on past, current, and (anticipated) future weather conditions. An additional seed head control spray was not an option, as it can adversely alter the way the grass plants grow, leading to scalping of the greens.
As you can see, there is a great deal of variability in Poa seeds from green to green. While #2 looks really good (in the picture above), just up the hill on #3 (in the picture below) it is a different story.
Lastly, we need to keep in mind that each green has a unique micro-climate, where growing conditions are different. Certainly #8 and #15 greens, while only being separated by a few hundred feet, are entirely different growing environments. These types of differences have long-term effects on which types of Poa will dominate the turf stand, as well as short-term effects on the timing of Poa seed production during the spring.
Currently, we are using several techniques to remove the seeds, and reduce their impact on the smoothness of the greens. One of the mechanical tools we turn to are verticutting units for our triplex mowers. This machine helps to remove horizontal growth in the green, as it also cuts away seeds, and lifts them up prior to the hand mowers following behind.
The bottom line is that what appeared to be excellent control this year, is "meh" at best. As always, we work to put together a strong science-based plan, which will yield great results. Our first treatment for seed head control actually started six months ago, late last fall, so it's definitely a bummer when it doesn't work out as we hoped. Once again, this illustrates that you'd need a really good crystal ball to hit the bullseye every time when working with Mother Nature.