Winter of 2014

After experiencing one of the longest coldest winters in recent memory, we have anxiously awaited to see what effect it would have on the turf. While most of the turf came through the winter fine, it is now apparent that we did suffer winterkill on a few of our greens.  The damage is most noticeable to the Poa annua on greens #4, #5 and #6.

Winterkill on #5 Green

WinterKill

Poa annua or annual bluegrass is a grass species that is particularly susceptible to winterkill primarily through a process known as crown hydration.  Crown hydration generally occurs in mid to late winter when a day or two of warm daytime temperatures causes snow to melt and collect in low areas.  The combination of warm temperatures and available water enables the grass plants to start absorbing water or hydrating.  If the warm weather is then followed by freezing temperatures, ice crystals form in the plant, rupturing cells and ultimately causing death.  Annual bluegrass tends to break dormancy quickly when subjected to above-freezing temperatures and free moisture and therefore is very susceptible to this kind of damage.  Creeping bentgrass on the other hand is late breaking dormancy and is virtually immune to crown hydration.  This is why when you see the greens that were affected you will notice that the annual bluegrass is severely damaged while the creeping bentgrass is very healthy.

Damaged Poa annua and healthy bentgrass

Recovery

In the short term we will look to reestablish the damaged areas of the greens as quickly as we can.  However this process can be agonizingly slow and challenging in the spring because of the cool, cloudy conditions that often persist.  The first step in promoting recovery is getting seed into the ground.  Once the weather warms and soil temperatures increase, we will begin the process of inter-seed creeping bentgrass into the damaged areas.  Although inter-seeding has given mixed results, success can be improved by using new improved bentgrass varieties and by utilizing tools such as the Job-Saver aerator attachment.  This tool produces numerous small, shallow holes for the seed to germinate in.  After seeding it may be necessary to apply a turf cover over the green to maintain adequate soil temperatures for germination to take place.  

Turf Cover on #5 Green

The second step to successful recovery is keeping traffic off the greens. Traffic sets tender, weak turf up for more injury.  Also newly emerging bentgrass seedlings are susceptible to wear injury.  Opening greens too early usually doubles the recovery time, and it reduces the amount of bentgrass established.  While no one hopes for winter injury, it does provide an opportunity for the existing bentgrasses to increase and to establish new and improved species of bentgrass. By increasing our bentgrass populations we would be less likely to encounter this type of damage in the future.  Other strategies employed in recovery will include reducing stress by mowing and rolling these greens less frequently, raising mowing heights, using solid front rollers on the greens mowers and providing light frequent fertilizer applications to stimulate new growth.  How long the recovery will take is difficult to say.  A lot will depend on the weather but I suspect it will take several weeks to completely heal.