It’s all about the putting surface, and turf selection is based primarily on which grass will provide the best surface. The grasses we use on putting green surfaces in the United States — or at least their ancestors — are native somewhere, but it’s not here.
Bentgrass originated in Europe, and bermudagrass in Africa. Zoysiagrass is from Asia, and seashore paspalum is from South Africa and South America. Nevertheless, each of these grasses is best suited to producing pristine putting surfaces in parts of the U.S.
Bentgrass prefers to live where it can wear a light jacket during summer evenings. However, in the late 1980s and ’90s, before golfers thought bermudagrass could provide an equivalent surface, it was common to see bentgrass in Louisiana, Mississippi, Alabama and even Florida. In Baton Rouge, La., where summer environmental conditions are similar to those in a steam room, one golf course had high-quality bentgrass putting surfaces and, quite likely, a fungicide budget larger than the entire budget of many courses in the region.
Since the early 2000s, the use of ultradwarf bermudagrass, which prefers crawfish, beignets and grits, has expanded to the north. Mike Richardson, Ph.D., did an informal survey and found ultradwarf bermudagrass putting surfaces as far north as Kentucky, Illinois, Indiana, Missouri and Virginia. Bermudagrass is not always adapted to the winters in these states and must be protected with covers when temperatures drop into the low 20s (F).
This past winter took a toll on some greens that weren’t covered, and even on some that were. Many of us in the upper South and the transition zone thought bermudagrass would greatly reduce maintenance costs and fungicide budgets compared with bentgrass. We were wrong. Bermudagrass excels in the summer but is susceptible to cool-weather diseases, including spring dead spot, mini-ring, leaf spot, cream leaf blight and cool-weather pythium. Fungicide requirements of bermudagrass in more northern environments have been higher than expected and often rival the costs associated with disease control on bentgrass.
There is increasing interest in zoysiagrass putting surfaces, which have been used in Japan for decades. Some golf courses in Japan have two greens per hole — zoysiagrass for summer and bentgrass for the cooler months. In the U.S., zoysiagrass use on greens wasn’t even considered until the release of the cultivar Diamond, which handles low light levels better than ultradwarf bermudagrass and is now used widely in the Southeast.
Development of zoysiagrass for putting greens continues, and Ambika Chandra, Ph.D., of Texas A&M AgriLife Dallas, recently released a new cultivar (experimental number DALZ 1308) that has very high quality, great winter color and produces an excellent putting surface (see Ultradwarf grasses: Beyond bermuda).
Efforts are underway to develop a cold-hardy zoysiagrass for greens. This could someday result in zoysiagrass greens in the transition zone. Could golfers in the middle of the country tolerate brown, dormant greens in fall, winter and early spring? Maybe not, but superintendents have excellent colorants that can provide a desirable green color during these months.
Because of its cold sensitivity, seashore paspalum is limited to Southern coastal regions and Florida and Hawaii. Its claim to fame is good tolerance to saline soils and water. Increased cold tolerance would be needed if this grass were to expand northward in the U.S.
Our experience with bentgrass and bermudagrass greens has clearly shown that, regardless of species, grasses maintained at heights at or below 0.125 inch are under stress. This stress results in susceptibility to diseases and environmental stresses, particularly when the species is in its off-season, which is midsummer for bentgrass, or winter, spring and fall for bermudagrass.
In parts of the country, there is no correct choice, and stress on either warm- or cool-season grasses is inevitable. Courses in these areas should recognize that, in certain years, one grass will perform better — thus making some courses appear superior — and that the opposite will occur in other years.
Ultimately, choosing a grass that results in less personal stress may be the most important choice in this profession, especially now, considering that so many grasses have the potential to produce an excellent putting surface.
Jack Fry, Ph.D., is a professor of turfgrass science and the director of the Rocky Ford Turfgrass Research Center at Kansas State University in Manhattan. He is a 21-year educator member of GCSAA.