Winter injury on Poa annua greens can develop from a number of causes, which is why the winter season creates feelings of uncertainty for so many in the Northeast. Creeping bentgrass greens, however, are much more tolerant of winter weather than Poa annua, so the amount of concern is significantly lower for courses that have creeping bentgrass.
At this point, most of the Northeast is blanketed with a decent snow pack. Some locations, however, have experienced a snow/rain mix that has left portions of golf courses covered with ice. In this situation, some turf managers will remove ice from Poa annua greens, while others are content with letting nature take its course. The frustrating fact is that turf injury can occur regardless of the decision made. Ice remaining on Poa annua greens for an extended period can cause anoxic conditions (low levels of oxygen), which can be lethal to turf. A freeze/thaw cycle on ice-covered Poa annua greens in late winter/early spring can cause severe injury, which is why many turf managers choose to remove the ice. On the other hand, ice removed during very low temperatures can be lethal as well, just adding to the difficult decision of ice removal from Poa annua greens.
Try assessing Poa annua health by cutting through the ice and taking several plugs from ice-covered greens. Bring the plugs indoors and place them under a grow-light for a few days and evaluate percent green-up. If a foul smell is detected immediately after breaking through the ice layer, turf injury has likely occurred to some extent via anoxia, and ice removal is necessary. However, Poa annua greens that grow in anoxic or anaerobic conditions for 45 days usually begin to lose cold temperature hardiness, so protect these recently cleared areas with a permeable cover or snow pack from a nearby, less-important area. If the turf greens up nicely and a foul odor isn’t detected, doing nothing is the best course of action.
Ice removal can be accomplished by breaking up the ice by hand or with aeration equipment (preferably older equipment). This process could cause more injury to weak turf than ice would, so caution is essential. The use of darkening agents (e.g. black topdressing sand) to accelerate melting can also work very well if temperatures are near or above 32 F with mostly sunny skies. This process is risky, too, because a refreeze is likely if all the water doesn’t drain off the surface and subfreezing temperatures occur. Obviously, there are risks with each ice removal strategy, but removal may be warranted if anoxic conditions have developed.
Winter injury and the decision to remove ice from putting greens is much more complex than the brief summary above. Feel free to contact our office for more specific information or review the links below which discuss the subject matter in more detail.
Upcoming Regional Turf Conferences:
New England Regional Turf Conference, Providence, RI, March 7-10th
New York State Turfgrass Association Regional Conference, Lake Placid, NY, March 16th
Met Golf Association/USGA Green Chairman Seminar, Williston, NY, March 22nd
USGA agronomists can provide insightful and invaluable information involving all areas of golf course maintenance, which will help maximize turf health, playability, and efficiency. Contact Dave Oatis, director firstname.lastname@example.org; Adam Moeller, agronomist email@example.com; or Jim Skorulski, senior agronomist firstname.lastname@example.org for a Turf Advisory Service visit this season.