Grass knows how to grow­­ — it’s the other stuff it needs help with.

As you southern supers read this, your northern peers are probably wrestling with greens covers, draining irrigation systems, and shivering in the cold as they get their courses buttoned up for the long winter ahead. It’s evident this time of year that there are many benefits to working in warmer climates, but there are also some added challenges. One is managing aggressive warm-season grasses on greens in places where the growing — and golfing — season never really ends.

Certified Golf Course Superintendent
Darren Davis has been at Olde Florida Golf Club in Naples, Florida, since its construction in 1992. Initially, the greens there were Tifdwarf, but they were re-grassed in 2000 to TifEagle.

“TifEagle has been a phenomenal grass for us, providing excellent putting surfaces,” says Davis. He notes that there is no dormant period in Naples, so the grass grows year-round and, obviously, produces thatch year-round.

“In the summer, when the grass is most actively growing, we are very aggressive with our thatch control/removal procedures,”
Davis explains.

Fortunately, summer is the “off” golf season at the club, with the majority of the seasonal residents leaving by June 1. That gives Davis and his crew a chance to really tackle thatch buildup on the greens.

“My first cultural practice every summer is to use a Graden walk-behind vertical mowing machine,” he states. “We use a 2-millimeter blade set on 1-inch spacing, and we go the full depth of the machine. So we have a 1.5-inch vertical mowing trench, which removes the thatch.”

Once that step is complete, topdressing is applied to try to incorporate as much sand as possible into the thatch layer. Davis changes his verticutting blades three times during the process because of wear.

“The purpose of that is that I want to maintain that 1.5-inch depth throughout the entire process; if I’m going to do this one time, we’re going to do it all the way,” he emphasizes. The switched-out blades are later reused on other parts of the course, such as tees and approaches.

The aggressive verticutting is followed by an equally aggressive core aeration, with a follow-up topdressing of straight sand.

“We do one aerification using a Toro ProCore 648 with 1.125-inch OD (0.75-inch ID) tines on 2-by-2-inch spacing, so it’s very tight,” Davis says. “That, combined with the Graden, removes enough thatch that these are the only cultural practices I need to use throughout the year to remove thatch.”

He says the goal is to remove a minimum of 20 percent of the organic matter every year, and these two processes together typically do a little better than that.

It does take the turf a little time to recover from this one-two punch, but Davis doesn’t believe in applying extra water or nutrients to help speed the healing process.

“That kind of defeats the purpose of what you’re trying to do. You’re doing aggressive cultural practices to try to remove thatch, and thatch is formed by growth. Growth is obviously a product of both food and water, so the last thing I want to do, if it’s not needed, is to apply additional nitrogen to produce additional thatch,” he explains.

Davis says performing the verticutting when the grass is most actively growing helps speed the healing process.

“I’m fortunate that the majority of my membership is seasonal,” he adds. “Having minimal play in the summertime allows me to be as aggressive as I possibly can be.”

At East Lake Golf Club in Atlanta, Certified Golf Course Superintendent Ralph Kepple faces similar thatch challenges, but doesn’t have the same window of opportunity to act so aggressively.

“In an ideal world, where we had no outings, I would like to do a light verticut — what I would call vertigrooming — about 0.1 inch deep about every two weeks, followed by topdressing,” he explains. He was only able to do that once last year.

The reality of regular corporate outings that keep the course in play seven days a week means Kepple often must rely on the use of Ultra Groomer (ATT TMSystem) cassettes on triplex greens units rather than actually verticutting.

“That doesn’t get down into the thatch or mat, but it does remove a lot of fat leaf blades and lifts up some of the blades that are laid over,” he states. “It helps us with the texture of the leaf blades, giving us a little finer plant.”

Whenever he is able to verticut, Kepple has three triplex units set up with verticutting reels featuring carbide-tipped blades.

“Some people don’t like the carbide tips because they cut a little wider grove, but without them we were wearing the blades out so fast and constantly having to adjust them,” he explains. At 0.1 inch, the process removes thatch, as well as opening up the canopy to help get sand down inside. He adds, “I think that’s the most difficult thing with all the ultradwarfs [East Lake has MiniVerde on its greens]; it’s such a dense canopy that it’s difficult to get the sand down underneath and into the crown.”

Some courses have switched to a much finer sand to help accomplish this, Kepple notes.

“We do that for short periods of time, usually around the Tour Championship [held in late September], because that sand definitely improves ball roll without having to do verticutting.”

However, he’s concerned about the longer-term consequences of continually using the finer sand.

“It’s a very different sand than the greens are constructed with, and my testing is showing that we’re developing a bit of a layer from that,” he explains.

In the coming year, Kepple will look for ways to verticut more frequently — possibly in the evenings — without impacting play for members and outings.

“The one time we were able to do it last year, we verticut in the late afternoon over the course of a couple days,” he explains. The course is closed for about 10 days each year in mid-July, which provides time for a major aeration and verticutting.

“Some years we’ve been able to do a 5/8-inch core aeration [on 1.25 inch center spacing] followed by two Graden verticuttings with sand injection running in two directions, which is pretty aggressive,” Kepple says. “It takes a lot of labor, and it takes the grass a while to recover from that, but it does a really good job.”

At Oak Hills Country Club in San Antonio, Superintendent Craig Felton manages his Champion greens (which have been in place for 17 years) with an emphasis on tough love.

“I think the more you beat it up, the better it gets, which isn’t necessarily the case with MiniVerde or TifEagle,” Felton says. “On the flip side, if you don’t beat it up, it’s probably not going to be very good.”

Felton verticuts his greens every Monday in two different directions throughout the growing months (May to August).

“Sometimes we do it again on Thursday,” he adds.

Felton says that on his Monday verticutting “we would really rip into them [in the past].” Now he uses a lighter touch.

“I’ll actually sand first, and then lightly verticut down and back, and then down and back in the other direction, and then brush. The members don’t even know I’ve done it by Tuesday,” he says. “And because it’s so light, I can go back on Thursday after lunch and verticut them again in just one direction down and back and not do anything else. So what we do is more of a tickle, but it’s done pretty frequently.”

He’s a little more aggressive with the verticutting right before the June and August aerifications.

On Mondays Felton applies a light coat of “bone-dry” sand with manual spreaders. This dry sand falls into the groves once the verticutter does its job.

“What doesn’t get verticut into the slice line, certainly gets vibrated into the canopy,” Felton says. “We dust with a topdressing twice a month during the growing season; I think the frequent topdressing helps me maintain the thatch layer where I don’t have to get super aggressive with verticutting.”

He backs off the verticutting frequency outside of the peak growing months, and does none at all in winter, when the grass moves in and out of dormancy depending on the weather.

“I wouldn’t stop doing it if I were overseeding greens, but I don’t, so I’m trying to develop a little thicker mat layer going into the winter because the greens need to sustain themselves [during the wear and tear of winter play],” Felton says.

He continues to use growth regulators, generally from May to November, and regularly rolls the greens during nonpeak growing months.

“You can’t go many days without doing something to them,” he concludes.

The Best Defense Against Disease? A Healthy Plant, of Course

When considering warm-season turf cultural practices, golf course superintendents should take a common-sense approach and remember that a healthy, actively growing plant is the best defense against diseases. Check out the following tips from Lane Tredway, Ph.D., senior technical representative for Syngenta Turf and Landscape:

  • Nitrogen fertilization — While specific rates and timings aren’t well-defined, the best practice is to tailor nitrogen rates and intervals to turf growth and quality. Nitrogen has the greatest impact on turf growth, and consequently has a major effect on disease susceptibility. Sufficient levels are particularly important in managing mini-ring caused by Rhizoctonia zeae, a disease that attacks stressed and slowly-growing turf.
  • Routine grooming and topdressing — These abrasive practices can stimulate leaf spot and other foliar diseases. Superintendents should adjust the frequency and intensity of these practices to the growth rate of the turf, and consider making a preventive fungicide application either before or shortly after topdressing and grooming operations.
  • Potassium Fertilization — While controversial, the fact is that sufficient potassium is proven to increase wear tolerance and leaf spot resistance in warm-season grasses. Excessive levels of potassium, or imbalances with other macronutrients, can be harmful, so superintendents should adjust their programs based on regular soil and tissue tests.