Unpredictable Weather February 29, 2016 By Bob Vavrek, regional director, Central Region

Only a few days of warm weather during late winter can deacclimate Poa annua to cold temperatures and make the turf highly susceptible to winterkill.

Golf facilities throughout the Central Region have experienced a fairly mild and uneventful winter so far. The golf economy was buoyed by the unanticipated revenue of late-season play, the dreaded polar vortex never materialized and no one is complaining about below-average heating bills. A few brief episodes of sweater weather have us eagerly waiting and watching for the arrival of robins and blooming forsythias.

Keep in mind winter is not over, and the wide swings in weather conditions during March can be just as stressful to grass species susceptible to winterkill as several months under solid ice. USGA funded research at the University of Massachusetts indicated that Poa annua will deacclimate – i.e., lose its ability to tolerate cold temperatures – much faster than creeping bentgrass as temperatures increase during late winter and early spring. Just a few consecutive days in the high 50s or low 60s can set the stage for significant losses of turf if the temperatures plunge back into the teens or single digits in the absence of insulating snow cover. This should come as no surprise considering how quickly Poa annua breaks dormancy and greens up during the spring.

As usual, low-lying, wet spots on the course will be most susceptible to winterkill when extreme shifts in temperature occur during March. These areas typically possess the highest percentage of Poa annua and also are more likely to collect water and experience crown hydration injury versus the turf across slopes and high spots that drain well.

The bad news is that playing surfaces dominated by Poa annua can suffer a great deal of turf loss in the blink of an eye when conditions for winterkill are ideal during March. Unfortunately, golfers tend to have far more patience with recovery procedures and are more willing to accept a valid explanation of why injury occurred after they experience a harsh winter versus a mild winter.

The good news is that a bout of winter stress is just what the doctor ordered if you have relatively new creeping bentgrass greens with minimal Poa annua contamination. An extreme drop in temperature can cull out those weak, young Poa annua plants that germinate and grow from seed unnoticed in greens during the previous fall/early winter. Never underestimate how much Poa annua encroachment can occur in a playing surface after an exceptionally mild winter.

Mother Nature will deal a few more hands before the ball washers are filled and the new flags flutter in a warm breeze. Until then, let's hope for the best but be prepared for whatever the weather dictates.


Central Region Agronomists:

Bob Vavrek, regional director –

John Daniels, agronomist –


Information on the USGA’s Course Consulting Service 

Contact the Green Section Staff

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