A frost delay?! But there wasn't any frost at my house."
The inevitable cry from the pro shop has come calling once again. Frost delays become the bane of our existence this time of year, and as much as we don't want to tell our guests they can't tee it up right away, it's our job as superintendents to protect the turf.
"Why do we have to wait for frost to clear?" would be the follow-up question, which has a not-so-simple answer - especially for someone who doesn't really want to hear it.
Understanding what causes frost to set up is the first logical step in trying to find out why it can be so devastating to golf course turf if not allowed to melt before play.
According to Katie Dupree, meteorologist at WFQX & WWTV in northern Michigan, "Frost occurs when the temperature cools to a point at or below the dew point and drops below freezing. You don't always have frost with temperatures below freezing, because if the temperature never reaches or is cooler than the dew point (dry air), then frost won't form."
Interestingly enough, "surface temperature" or "ambient temperature" is an official measurement that is taken between 4.1 and 6.6 feet off the ground. Since cold air is more dense, it will settle below what is the measured surface temperature and keep the air at true ground level below freezing after the thermometer rises above it.
"If the ground has been frozen," Dupree adds, "this, too, can create frost at temperature readings above freezing." This would also explain why frost is more prevalent in the valleys and hollows of the golf course.
OK, then. Frozen ground, frosty grass. So what's the problem?
According to Keith Happ, senior agronomist for the United States Golf Association's Green Section, all the variables have to be in place for damage to occur it's just difficult to predict the "perfect storm" for turf damage.
"Physiologically, there's the potential damage to turf from the frozen plant cells rupturing as they are exposed to traffic," Happ says. "This damage is irreversible. The plant may eventually grow out of it, but surface quality and playability will suffer in the meantime."
The degree of freezing that will ultimately cause damage is difficult to quantify as there are so many variables to consider such as shade, elevation, grass type, soil type and soil moisture, Happ adds.
"While there may be times when brown grass doesn't result, there still is damage that predisposes the plant to other problems," he notes.
I think we can all understand Happ's point, but what about the guy who says, "I've stepped on frosted grass plenty of times before and didn't see any footprints or damage at all - I don't believe you."
Darin Bevard, director of the USGA Green Section's Mid-Atlantic Region. offered up his analogy.
"Consider the flu or common cold. Obviously, you are constantly exposed to germs over the course of a normal day," Bevard says. "However, you don't get infected with a cold or flu every time you go out in public.
There are a variety of variables that have to come together when you are exposed to these germs for you to catch a cold."
When you're dealing with living organisms, it's sometimes difficult to pinpoint the catalyst for problems, Bevard says.
"I tell people that you may walk on frost eight out of 10 times and never see damage," he says. "The problem is that I can't tell you when the two times that you will cause severe damage will be. It's kind of like a turf version of Russian roulette."
If you think about it, I'm pretty sure golfers would find it disappointing to putt on frosted greens anyway.
Jim Black is assistant superintendent at Grand Traverse Resort in Acme, Mich. He can be reached at firstname.lastname@example.org.