They Don’t Call It ANNUAL Bluegrass For Nothing

By Bob Vavrek, senior agronomist, North Central Region
January 17, 2012

Unfortunately, when the old Poa in a green dies from winter stress, it’s usually the same, if not weaker, biotypes of Poa that eventually fill into the thin and bare areas from seed already present in the soil.  This tends to promote an endless cycle of turf loss from winter and/or summer stress that will become more prevalent if the predictions for milder winters and hotter summers come true.  

No one seems to be overly concerned with winter injury as we enter 2012. This low level of anxiety is understandable considering the extended period of unusually mild weather throughout the Region leading up to the New Year. A number of courses even managed to garner some unexpected, but more than welcome, revenue from late season green fees due to the absence of snowfall during the holidays. 

Yet, I would argue that it’s the mild winters that should be feared the most when Poa annua or annual bluegrass is a significant component of the playing surfaces. Like most of us, Poa doesn’t like change or extremes. It sure didn’t respond favorably to the abrupt transition from a cool spring to an oppressively hot and humid July and August last summer.  Similarly, Poa at many of the Region’s courses had difficulty surviving thaw/freeze events and the occasional midwinter rainfall over snow cover that sealed off and suffocated low lying areas of greens and fairways.    

The one-two punch of winterkill and summer stress caused considerable losses of turf at many courses these past two seasons. Maybe you were persistent and fortunate enough to establish bentgrass into thin or dead areas of greens and significantly increase the ratio of bent to Poa in the putting surface. If so, you were in the minority. The best efforts of many resulted in little more than the eventual re-establishment of Poa annua into problem areas from seed already present in the soil. 

Unfortunately, it’s never the desirable perennial type of Poa that we find filling into the dead spots. As a rule, the seedy, fast growing, clumpy biotype of annual Poa is what finally provides the majority of turf cover for a devastated putting green and this same Poa will be extra-susceptible to heat, drought, diseases, and winter stress for the upcoming seasons. In the absence of these stresses and extremes the annual types may slowly transition into a more perennial type of Poa, but this takes time and weather patterns conducive to the transition, which have not been overly cooperative in recent years.

Then again, why should this come as any surprise? After all, the name of the grass is annual bluegrass and we often forget that annual plants live to produce seed and die. However, if the climatologists are correct, we can expect more mild winters and more extreme summers across the upper Midwest, and these predictions do not bode well for Poa growing old enough to reach the perennial stage. If true, I can’t help but wonder if the most sustainable option for old Poa greens in this Region is renovation to creeping bentgrass - not a bad topic for a regional update in the future.

Nevertheless, there is always hope that climatologists are more or less specialized meteorologists…and “we all know a weather forecast is never, ever wrong.” So keep the faith for the New Year that the mild weather so far will lead to an early, warm spring and no surprises in between.

Source:  Bob Vavrek, or 262-797-8743 


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