The sustained record-breaking heat across much of the U.S. this summer, combined with high humidity and occasional heavy rain, is killing the greens on many golf courses. A handful of high-profile courses have already had to close, and if the heat continues, others are likely to follow. Golfers themselves deserve part of the blame for insisting that putting surfaces be mown short and fast even in weather conditions in which such practices are almost certain to ruin them.
Huntingdon Valley Country Club outside Philadelphia, which dates from 1897, shut two of its three nines two weeks ago because of serious turf disease caused by the hot, wet weather. The Philadelphia area in July had 17 days of 90-degree-plus weather, six more than average, mixed with flooding thunderstorms of up to 4 inches.
Members at the Golf Club at Cuscowilla, east of Atlanta, received letters this week that the club's highly regarded Ben Crenshaw-Bill Coore course would be closed for eight to 10 weeks so that the wilted greens can be completely replanted. The Ansley Golf Club broke similar news to members about the club's in-town Atlanta course. "The continued, excessive heat and humidity have put our greens into a critical situation and the possibility of saving many of them is remote," said a letter from the grounds-committee chairman. Even Winged Foot in Mamaroneck, N.Y., the site of five U.S. Opens, is having serious weather-related problems with its turf.
The U.S. Golf Association last week issued a special "turf-loss advisory" to courses in the Mid-Atlantic states, urgently advising greenkeepers to institute "defensive maintenance and management programs" until the weather crisis ends. Most of the danger is to greens planted in creeping bentgrass and annual bluegrass (also known as poa annua).
"Physiologically, these are cool-season grasses that do very well when the air temperature is 60 to 75 degrees," said Clark Throssell, director of research for the Golf Course Superintendents Association of America. "They can cope with a few days of 90-degree weather every summer, but when that kind of heat lasts for days at a time, they have extreme difficulty."
Temperatures for weather reports are measured in the shade, but greens baking in the midday sun can reach 120 or 130 degrees. When grass spends too much time in soil that hot, it starts to thin out, turn yellow and wither. Most bentgrass strains will collapse entirely with prolonged exposure to 106-degree soil. The grass doesn't go dormant—it dies.
Grass does have a mechanism to cool itself. It's called evapotranspiration and is analogous to perspiration. The roots draw up water from the soil and it evaporates through the plant's leaves, dissipating heat. But when greens are scalped to a quarter-inch, an eighth of an inch and even shorter, the leaf surface available for transpiration declines.
Prolonged heat causes other problems. One is that root systems shrink, sometimes to within a half-inch of the surface, reducing the amount of water drawn up to the top. Humidity and heavy rain make things even worse. Humidity retards evaporation, while soggy soil stays hot longer than dry soil does. Puddles and saturated soil also create barriers that prevent needed oxygen from getting to the roots.
Even when the combination of these factors doesn't kill bentgrass and poa annua greens outright, it weakens the turf significantly and renders greens more susceptible to fungus and disease.
Bermuda grass, by contrast, thrives in temperatures in the 80s and 90s but cannot survive cold winters. That makes Bermuda the logical choice for courses in the Deep South. High-prestige clubs in the so-called transition zone, which includes parts of Georgia, the Carolinas, Tennessee, Texas and the Midwest, have long put a premium on having bentgrass greens because of Bermuda's historic liabilities as a putting surface. Bermuda greens were coarser, bumpier and had problems with excessive "grain," caused by the bristly blades growing in one direction (generally toward the setting sun) instead of vertically and thus unduly influencing the speed and direction of putts. Colonial Country Club in Fort Worth, Texas, claims to be the first course south of the Mason-Dixon line to install bentgrass greens, in 1936. Hundreds of clubs have followed since.
But they pay the price, even in years with less brutal summers than this one. Colonial, for instance, has five or six fans around every green, stirring up 25-mile-per-hour breezes around the clock to help keep the greens cool. The club in summer has four full-time employees who do nothing but hand-water the hot spots on the greens every day. "Keeping the greens alive till that first cool spell in September is all we hope for," said the club's head pro, Dow Finsterwald Jr.
When hot weather hits bentgrass courses, course superintendents also raise mowing heights. That yields more leaf surface and improves evapotranspiration but can slow down putts by a foot or more on the Stimpmeter, which measures green speed. "Better slow grass than no grass" is a mantra among greenkeepers, but the pressure from golfers to keep the greens rolling fast is relentless.
During the hot summer of 2007, ground crews at East Lake Golf Club in Atlanta, home of the PGA Tour's Tour Championship, tried every trick in the book to keep the club's bentgrass greens healthy. They hand-watered each green every 30 minutes during the hottest days, just enough to cool off the grass blades but not enough to add moisture to the soil. They ran fans and cut the greens with walk-behind mowers rather than heavy triplex riding machines, to reduce stress.
But nothing did much good. "It's such a helpless feeling. You watch the greens turn yellow and you know they're going to collapse, but there's just nothing more you can do," said Ralph Kepple, East Lake's superintendent.
For the 2008 season, East Lake replanted its greens in one of the new "ultra dwarf" strains of Bermuda that are hard for most golfers to distinguish from bentgrass, in terms of performance. The club is pleased with the decision, Mr. Kepple said—especially this summer.
Augusta National, the home of the Masters 90 miles east of Atlanta, is in an area that is often 10 degrees hotter in the summer, but it easily maintains bentgrass greens. The main reason: The course is closed for play in the summer. That's a luxury very few courses can even consider.
—Email John Paul at golfjournal@wsj.com
