FEATURES
The Control Center
Keep Winter Injury in Check

by Anne Morris

Although controlling nature is not an option, there are some steps you can take to help your course survive harsh winter weather conditions.

Winterkill is a catchall term that refers to turfgrass loss during the winter. In its broadest sense, winterkill goes beyond ice and snow. States that rarely see those conditions might suffer freeze damage or desiccation, the drying out of plant material under low temperature and drought conditions.

Among the conditions that can affect winterkill are surface drainage, hardening, temperature, moisture, wind, disease (such as snow mold) and shade. Crown hydration injury is a big problem, especially during times of thawing and refreezing. Ice crystals can form in the crown of the plant and rupture the plant cells, killing the plant.

Jim Skorulski, USGA agronomist for the Northeast, said that there are ways that superintendents can fight winterkill. “There are a few things you can do, long term and short term,” he said.

Photos Courtesy of Peter Hasak, Tedesco Country Club, Marblehead, Mass. The number 4 green at Tedesco Country Club suffered damage after the winter of 2002-2003.   Shaded areas may be more prone to damage from winter conditions.

“Long term, you can make sure the turf is getting the full sun, because the plant requires the sun to gain its cold temperature hardness. You’ve got a couple of strikes against you if you have shady turf going into winter,” he said.

Greens with poor surface drainage that hold any kind of surface water are going to be more prone to injury, according to Skorulski. “Knowing that, you might want to look at a winter protection cover system if you’re far enough north to try to prevent the water from puddling and hydrating the turf. Having water on top of a non-permeable cover is one thing, but it’s not as bad as having it saturating the turf,” he said.

Deciding what to use should be on a case-by-case basis. “They are not for everybody,” he said. “But, if you’re located in the North and you don’t have a consistent snowpack all year, you do get freeze-thaw cycles. And, if you have poor surface drainage, then non-permeable covers, with or without insulating material, are a good type.” Though not a guarantee, he said that they do help.

Another suggestion Skorulski made was cutting temporary trenches through pockets to get the water flowing out of any areas where it is collecting. Another possibility is cutting dry wells in hopes that any surface water will go downward and off the surface.

“Ultimately, regarding those low pockets is going to give you the solution in a lot of cases,” Skorulski said.

He also recommends growing bentgrass. “That’s the main thing,” he said, “because Poa is the most susceptible to cold temperatures. Any steps you can take to growing bentgrass, you’re going to have a better chance of surviving the winter.”

Dr. David Minner, professor of horticulture and extension specialist at Iowa State University, has been studying golf course winter injury. His study was funded by the GCSAA, with an eye to advising superintendents on how to keep this next winter from being as harmful as the one they came to grips with in March 2008, when he wrote, “In some areas of Iowa we experienced 100-plus days of continuous ice and snow.”

It came on the heels of years when the winterkill was not too severe in Iowa.

This past year, annual bluegrass and perennial ryegrass in low-mow areas were particularly injured, while creeping bentgrass and Kentucky bluegrass fared better. An estimated 70 percent of Iowa’s 425 golf courses suffered winter damage of one kind or another.

In fall 2007, Iowa experienced milder than usual temperatures followed by a frigid winter. Usually, fall gets progressively colder, allowing for gradual hardening of the turf.

Tedesco Country Club in Marblehead, Mass., was damaged by winter conditions during 2002-2003.

“It is important to ‘harden off’ the grass before winter,” Minner said. “Avoid nitrogen application that causes lush growth before winter. Be sure potassium is not deficient. Don’t cover too early.

“Ideally, you want several cycles of frost in the ground with sunny days so that the plants can still accumulate carbohydrates.”

Here’s how hardening works: Moisture content decreases in the plant, leaving it with a higher sugar content, which acts as antifreeze and prepares the plant to better survive freezing.

Raising the cutting height in late summer or early fall can also help increase carbohydrate levels in the plant.

Minner warned that ice or snow cover on top of non-hardened grass is likely to cause some type of winter injury, so do what you can to encourage the hardening process.

It was his observation that areas of the golf course where water collected tended to suffer damage. The answer to that: improve drainage wherever you can. Water that collects in low areas can freeze and thaw rapidly, causing additional damage to turf.

He also recommends getting rid of trees that shade the course. It was clear to observers that shady areas suffered more than sunny ones during winter weather. Adequate sunlight is important for photosynthesis during the hardening process.

Use of covers to reduce winter damage can be effective, especially if desiccation is one of the main problems. They tend to minimize water loss from frozen turf. Popular choices include GreenJacket, a non-permeable cover from Sto-Cote Products in Wisconsin (www.greenjacket.com), and Winter Jacket, a permeable cover from IVI-GOLF (www.ivi-golf.com). Research suggests that the non-permeable covers may be preferable, but there are pros and cons to both.

One important thing to remember is to remove the covers promptly once the weather improves, and dry out any areas of the course where water stands. As soon as you can, reestablish grass in damaged areas through seeding or sodding. Maybe this winter won’t be so bad.

Anne Morris is a freelance writer and frequent contributor to Superintendent. She resides in Austin, Texas.