The summer heat and drought reveal the differences in the growth habits of bentgrass and Poa. It’s the one time of year when even golfers can see the difference between grass varieties on the putting greens.
The Poa-to-bentgrass transition in New York is an important conversion during the summer. If converting to bentgrass, this is the ideal time—bentgrass thrives in the heat, while Poa does not. In the heat and dryness, it provides the best time to kill Poa. It’s also the best time to seed bentgrass, since Poa is less likely to reestablish.
This conversation began with retired golf course superintendent Rick Slattery, formerly of Locust Hill, who discussed his spring strategy for promoting creeping bentgrass over Poa annua. In a recent Clippings Podcast episode, he explained how holding off on spring irrigation helps weaken Poa during a transition and how targeted inputs can manage high-Poa areas, such as shaded or poorly draining greens.
First, let’s explore each grass variety
Poa has often been viewed as the species that delivers the highest performance. It can produce the fastest and firmest greens and doesn’t become thatchy, due to its growth habit. Poa can be found at top courses like Bethpage Black and Oakmont, known for their fast putting surfaces. But Poa also requires significantly more inputs: more water, more fertilizer, and more pesticide applications to protect against disease and pests. The annual bluegrass weevil, arguably the most damaging turf pest in the state, feeds exclusively on Poa. So while Poa can produce top-tier greens, it’s also the most demanding.
Bentgrass, on the other hand, needs less. It performs better when watered less, fertilized less, and sprayed less. But it does have its drawbacks: it can grow thatchy, and its soft, puffy roots can lead to slow greens if not properly managed through consistent cultural practices.
Most courses have both grasses in play. One would find bent-Poa mixes on fairways, where there’s larger acreage and often less intensive management.
This transition is about more than grass. Conservation of time, money, and resources, along with the reduced need for chemical inputs, is what makes the conversation important. However, it’s also a conversation that requires trust. Golf course superintendents need their memberships and boards to understand that this is a long-term approach with long-term benefits.
New York Examples
Rick Slattery’s approach at Locust Hill could be described as “slow and painful”: shutting off the water, take away the fertilizer, and let the Poa die. Then over time, evolution should take hold and allow the bentgrass to come in.
At Corning Country Club, John Hoyle opted for a complete reset. In this case study, the operation killed all the grass and replanted it with the newest bentgrass varieties. Once established it didn’t need to water it as much, or spray. It saved a lot. Hoyle outlined his process in a blog on the NYGCF BMP website: https://nysgolfbmp.cals.cornell.edu/blog/
The Cornell Turfgrass team brought together both perspectives—and an evidence-based approach to the Poa-to-bentgrass transition—in their guide: Converting Fairways to Creeping Bentgrass to Reduce Inputs. Maybe a good read or review for the summer season.