Turfgrass surfaces under heavy traffic stress are some of the most difficult to maintain on a golf course. A great example is collars around putting greens. While putting greens receive all of the attention, poor collars can detract from the aesthetics and functionality of the entire green complex.
Collars are traditionally grown on native soils and maintained at a higher height of cut than putting greens. Collars are often where walking greens mowers are turned and foot traffic is concentrated. These factors alone make maintenance requirements different than their neighboring putting greens. Moreover, when warm-season collars encircle cool-season putting greens, the difficulty in maintenance is amplified.
We often see warm-season (bermudagrass or zoysiagrass) collars around cool-season (creeping bentgrass) putting greens in the transition zone. The growth habits, fertility requirements, plant growth regulator (PGR) tolerance, and seasonality of environmental stress are very different between warm-season collars and cool-season putting greens. It is worth mentioning that chemical weed control and prevention is very difficult in warm-season collars when they are next to vulnerable cool-season putting greens.
Various forms of winter injury to warm-season collars around bentgrass putting greens is often evident at this time of year. Warm-season collars around bermudagrass putting greens receive aeration, fertility and PGR programs based on the needs of the warm-season putting greens. They are also covered along with the bermudagrass putting greens when lethal temperatures are forecast. Conversely, warm-season collars around cool-season putting greens are often maintained based on the needs of the cool-season putting greens. Fertility, aeration and PGR programs tailored to cool-season putting greens are often detrimental to the collars. Winter injury is often observed in collars for a variety of reasons, including:
- Winter traffic – including mowing the cool-season putting greens during winter – can damage warm-season collars while they are not actively growing. This is often worse in pinch points between bunkers and putting greens.
- Overspray from PGR programs designed for cool-season putting greens is detrimental to warm-season collars.
- Early spring aeration and sand topdressing programs on cool-season putting greens damage warm-season collars that are not yet growing.
- Warm-season collars around cool-season putting greens are often under-fertilized and not regularly aerated during the warmer months.
- Collars in sand-based soils are susceptible to drying out and suffering damage from winter desiccation.
What can be done to prevent winter injury in warm-season collars? While some things may be out of your control, these practices will improve your collars’ chance of survival:
- Use a triplex to mow bentgrass putting greens in the winter months to reduce traffic in collars. Some may dispute this point, but I rarely see injury to collars when courses stop walk-mowing in the winter. Taking a little extra time to turn the triplex away from the collar also helps.
- If walk mowing, the use of turning boards may help protect collars. This is especially important in areas of concentrated traffic.
- Solid-tine aerate and fertilize warm-season collars monthly in the summer. Core-aerate collars at least once during their primary growing season.
- Replace collars with warm-season turfgrasses that have improved cold tolerance.
- Prevent PGR overspray from putting green applications with GPS-guided, individual-nozzle-control spray equipment.
- Apply wetting agents in the fall and early winter on warm-season collars to reduce the risk of winter desiccation. Monitor soil moisture content in the winter as well.
- Cover warm-season collars with pine straw or turf covers when temperatures are forecast to be below 20 degrees Fahrenheit.
- Delay aeration of bentgrass putting greens until warm-season collars are actively growing. Avoid collars when dragging or brushing in sand following core aeration.
Maintaining healthy turfgrass surfaces on putting greens and collars is critical to the golf experience. Differences between warm-season collars and cool-season putting greens make these areas very difficult to manage in the Southeast, but focusing on the specific needs of each grass throughout the year is paramount to success.
Southeast Region Agronomists:
Chris Hartwiger, director, USGA Course Consulting Service – chartwiger@usga.org
Steve Kammerer, Ph.D., senior consulting agronomist – skammerer@usga.org
Jordan Booth, Ph.D., agronomist – jbooth@usga.org