The putting greens at Scarsdale Golf Club had become increasingly unreliable and difficult to maintain during periods of extreme weather due to high populations of Poa annua – i.e., annual bluegrass. Playing-quality standards could not be consistently met throughout the season and significant turf loss occurred several times due to winter injury, summer stress and disease. Although the greens had been interseeded with creeping bentgrass many times over the years, little progress was made and the greens remained predominantly annual bluegrass. It became clear that a more aggressive plan was necessary. The tipping point arrived during the summer of 2011 when extreme weather resulted in substantial turf loss on several greens.
The club formed a combined Golf and Grounds Committee to evaluate several options including continuing with a gradual transition to creeping bentgrass over several years, spraying the greens with a nonselective herbicide and interseeding, and completely rebuilding the greens and sodding. After consulting with a USGA agronomist, the Board of Governors approved an aggressive plan for transitioning the greens to bentgrass.
Following the turf loss in 2011, the greens were cultivated with a variety of implements and seeded with creeping bentgrass. The most crucial step in the process was closing the most-damaged greens for four weeks to eliminate traffic and allow the bentgrass time to become established. When the greens were reopened in early September, full turf cover had been restored and the greens were reopened by early September with significantly more bentgrass than prior to the cultivation and seeding.
Beginning in 2012, cultural practices were adjusted to favor bentgrass. Light applications of paclobutrazol, a plant growth regulator, were made to suppress annual bluegrass. Seedhead-suppression treatments were eliminated to further weaken the annual bluegrass. The club discontinued pest control applications that normally protected annual bluegrass from summer patch, anthracnose, and annual bluegrass weevils. Nitrogen fertility was also reduced, giving bentgrass an additional competitive advantage.
These steps weakened the remaining annual bluegrass populations and noticeable thinning occurred in late June and early July. Thousands of 3-inch bentgrass plugs were planted in the thin areas and, while bentgrass populations thrived, nearly 70-80 percent of the existing annual bluegrass was under stress or dead by the end of July. Irrigation was significantly reduced before an early August aeration and seeding date, causing extreme stress and more thinning of annual bluegrass populations. The greens were then aerated, interseeded and closed for six weeks to allow for further creeping bentgrass establishment. The greens were reopened in mid-September.
The same basic cultural program was followed in 2013, except that bentgrass populations were so high that it was not necessary to close the greens after aeration and seeding in August. The remaining annual bluegrass was once again under stress during the summer, but it was barely evident because the population had become so low.