Features Agronomy
Winter damage: Worst winter in 40 years leaves its mark

Most regions across Canada experienced their worst winter season in 40 years, and the extreme cold took its toll on many golf courses.

Winter damage ranged from moderate to severe on these courses, particularly on greens, delaying courses’ projected openings by two weeks or more for the most part.

Golf courses whose putting greens are primarily grown to annual bluegrass took the biggest hit. Severe turfgrass injury and even death was experienced at several Canadian golf courses.

In mid-April, USGA Green Section agronomist Adam Moeller visited Sunningdale Golf & Country Club in London, Ont. to speak to a gathering of superintendents, general managers and course owners about the impact of the past winter, and suggested several strategies which can help lessen the blow in future years.

The forum was put together by the Greater London Association of Golf Superintendents (GLAGS).

Following his presentation, Moeller and Sunningdale superintendent Tim Webb led a tour of select greens on the golf course to observe some of the winter damage first hand.

“It doesn’t matter what killed your grass for the most part,” Moeller said. “It’s just how we can prevent things or minimize it in the future. There are few different ways the grass can die from winter.”

There are four main factors which lead to winter injury: direct cold temperature injury, crown hydration damage, ice encasement and suffocation, and desiccation.

The most common of the four is crown hydration which is caused by the cycle of freezing and thawing of snow.

At the time of his visit, Moeller said he wasn’t able to determine the precise severity of winter damage to golf courses in the region. He said, however, he had a good indication of what was weak and what might bounce back.

Although his focus was on damaged greens, Moeller suspected fairways would likely take longer to recover due to such factors as ongoing cart traffic. He speculated fairways could take the entire season to recover.

Addressing his audience of mainly superintendents, Moeller said he figured most in the room had annual bluegrass as the dominant species on their greens. The common weed grass which is maintained on greens at numerous North American golf greens, including seven of the top 10-ranked U.S. courses, is much more susceptible to winter injury than bentgrass. He said he had no reports of any significant winter injury to bentgrass during his early spring travels.

He said superintendents who maintain poa annua greens have been lucky to escape serious winter damage over the years, but added the past winter is a harsh reminder of the weakness of annual bluegrass.

Poa is the weakest of all grasses in its tolerance to cold temperatures. If the plant is exposed to temperatures of about minus 21 degrees Celsius, about 50 per cent of the grass will live in a best case scenario situation. In a normal winter, there is sufficient snow cover to insulate annual bluegrass. Moeller said it’s akin to a bear hibernating over the winter. Food and carbohydrates are stored in the late fall, and the grass is rested through the winter. As the winter season continues, poa loses its cold temperature hardiness, especially if there is a warmup here or there. If temperatures soar to 10 or 12 degrees for a day or two, the poa is fooled into thinking spring has arrived, and suddenly it’s not as tolerant of cold temperatures.
“That’s one of the real challenges we see with this grass.”

When the plant is tricked into thinking it’s spring, it wants to actively start growing and taking up moisture. A cold snap can be lethal to it.

Creeping bentgrass, by comparison, is considerably more capable of tolerating much colder temperatures. It’s a hardier plant, and can usually tolerate temperatures of minus 35 degrees before 50 per cent of the plant dies.

Ice cover on greens was experienced for prolonged periods this past winter. Encasement in ice one to two inches thick was seen in several locations. In a typical year, a thaw of sorts is experienced in January or early February.

“This year it seemed like it never happened,” Moeller said, adding ice cover lasted anywhere from 40 to 70 days. “That’s a long time to go without breathing. There’s just not any air getting to that turfgrass plant.”

In cases of prolonged ice cover, the turfgrass plant suffers from anoxia, or a lack of oxygen. A heavy snow pack can also prevent oxygen from getting into the soil profile.

Moeller said the plant is trying to hold on beneath the ice cover, waiting for spring, but the longer ice cover remains, the weaker the turf is going to be.

Desiccation, in which the plant dries out, is more of an occurrence at open, windswept golf courses.

Moeller said the plant builds up its own level of winter tolerance or cold temperature hardiness in the fall. If it doesn’t have good cold temperature hardiness, it will be more prone to problems.

As soil temperatures begin to warm, and a few consecutive days of temperatures reaching 10 or 12 degrees are realized during the winter, the plant starts to lose its cold temperature hardiness, especially on poa putting greens. The more thatch or more organic matter present in the soil, the more rapid will be the loss of the plant’s hardiness. The same occurrence will be experienced with ice cover.

“I think that’s the biggest challenge superintendents were facing this year. As they had ice longer and longer, that plant got weaker and weaker, and it lost its stored energy and cold temperature hardiness.”

A superintendent may consider physical removal of ice from his greens after 45 or 50 days, but is then subjecting his turf to cold temperatures.

“You’re stuck between a rock and hard place. There’s no good solution.”

Once its hardiness is lost, the turf is weaker, has no energy nor any stored carbohydrates.

“It’s got a whole lot of nothing right now.”

Superintendents are limited as to what they can do to prevent the type of extensive winter injury experienced this year, but Moeller said the best way is a combination of regrassing or rebuilding their greens with a more reliable grass on the surface.
Regrassing or rebuilding greens is “not an easy pill to swallow,” he said, adding some courses in the Greater Toronto Area will be doing that this spring.

“It’s not a perfect solution,” Moeller said. “It comes with a few challenges aside from shutting your course down and the expense of doing all those things, but bentgrass is a much, much more reliable grass. It’s not as easy as taking the old carpet off and putting the new carpet down. But that’s really the best long-term solution.”

In the meantime, if a superintendent wishes to continue to maintain a mixed stand of annual bluegrass and bentgrass, from a cultural standpoint he needs his grass a healthy as possible going into winter.

“That’s easier said than done. You want to maximize the plant’s ability to be prepared for winter and maximize your cold temperature hardiness.”

One of the biggest necessities required for promoting cold temperature hardiness is adequate sunlight. Moeller said it’s just as important to have maximum sunlight on putting greens during the winter months as it is in the summer.

“We see it time and time again…greens that are more severely damaged from winter injury are the ones that have shade issues the whole year, but also shade issues in the afternoon.”

When a winter thaw occurs and temperatures reach eight to 10 degrees, causing snow and ice to melt rapidly, afternoon shade will act like a switch, and suddenly the temperature drops to zero with no gradual decline. Ice freezes up quickly and more damage is realized.

Sufficient sunlight must reach the green for the entire day to allow the plant to build up its carbohydrates and energy reserves to prepare it for winter.

The most damaging trees for promoting shade, Moeller said, are coniferous species which don’t lose their leaves. The shade they cast weakens the turf.

Focusing on a green’s growing environment should be the superintendent’s primary consideration, he said.

“If you correct some of the growing environment challenges (such as extensive shade), you’re probably not only going to make the poa happier, you should see bentgrass populations in your putting greens improve over time naturally.”

Aside from removing or thinning problem trees, there are other practices which can be done to improve annual bluegrass’ chances of better surviving the winter. Raising the mowing height on greens throughout the fall season is one means to improve the plant’s ability to maximize its cold temperature hardiness.

“Unfortunately, we’re cutting our grass so low now that if we raise the height of cut, it’s still not enough.”

Only 20 to 30 years ago, mowing heights were typically between .140 and .156 inches with fall heights raised to between .160 and .175 inches. Today, greens are being cut at .125 inches and raised in the fall to .140, which is only a negligible increase and is equal to the typical height of cut only a few decades ago.

Member expectations for faster greens have driven mowing heights lower over the years, creating increased agronomic challenges for superintendents.

Moeller urged careful fall fertility, noting that overfertilizing greens in the late fall will produce more growth than desired, resulting in compromised carbohydrate storage. Consequently, the plant will have lesser cold temperature hardiness.

Keeping greens drier in late fall without additional irrigation is encouraged. Late fall rains which don’t dry out set the turf up for more winter injury problems because the turf doesn’t have the chance to acclimate and prepare itself for winter. That leads to the need for improved drainage to allow the soil to properly dry out.

“If you can improve drainage in your putting greens, it’s another step in the right direction. It improves the plant’s ability to tolerate winter injury.”

If a golf course has native soils which don’t drain especially well, sand channel drainage is a wise investment, Moeller said. It will not only improve things from a carbohydrate storage standpoint and better tolerance to cold temperatures, it will make a significant difference in the summer. Sand channel drainage is not likely to prevent winter damage, he said, but if it can keep greens drier after a late fall rainfall, it will put the plant in a better situation.

Better surface drainage is also recommended to ensure water fully moves off the surface and is not left to pond in areas.
Deep tine aeration of greens in late fall before soil freeze-up aids in better winter drainage.

Regular core aeration and topdressing—a practice which should be performed anyway for improved playability—will help to manage surface organic matter. Thatchy turf holds onto moisture longer which increases the chances of winter injury. Addressing surface organic matter will help “to lessen the blow,” Moeller said.

Superintendents who adopt each of those cultural practices yet still experience extensive winter damage on a frequent basis may wish to consider covering their greens in the winter, he said.

Covers may or may not be the solution, he cautioned, noting they may not be for everyone. He cited the expense of both the product and labour involved in their proper installation, storage requirements and the challenge associated with putting them in place. A typical cover is larger than a common meeting room, and two individuals trying to put one down on a windy day can be an exercise in futility. If it’s not installed properly, it will blow away.

“They are not easy to manage, but they can definitely help you if you’ve got a certain situation where you’ve had a history of damage at your site.”

Winter protection covers are designed to prevent water from reaching the putting green surface in the form of rain and snow melt as well as offering protection from ice. They will also stabilize temperatures, acting as a blanket in extreme cold.
“They can improve your odds for success in the right situation.”

The combination of a cover and snow on top provides the best insulation. Moeller cautioned against covers being put down too early, noting that if they cover pre-dormant turf, they might leave the plant not as tolerant as it should be to cold temperatures.

Timing of cover removal is important, he said, suggesting they should be removed earlier rather than later. He said in the event of a mild winter, it could get too warm beneath the cover, causing the grass to start growing and becoming prone to disease.

Once temperatures under the covers consistently reach about 10 or 11 degrees, the turf is starting to “wake up,” and that’s when they should be removed.

“For the most part, I think covers can work pretty well if you manage them correctly.”

Superintendents are apt to manually remove ice cover on their greens at a certain point during the winter, but it becomes a roll of the dice, Moeller said.

“It’s not an easy decision. No matter what you do, you can second guess yourself.”

During periods of extended ice cover, superintendents will combine science with guesswork in determining when to break up ice. There are some rules of thumb to follow to help to make more informed decisions and reduce the amount of guesswork.
When contemplating ice breakup, Moeller recommended noting where the ice is, its thickness and its ice type, adding not all ice is the same. If it is thick and clear, it’s usually the worst. If the ice is cloudy, it suggests there is some air movement inside. It is important to know how long the ice has been in place.

Research shows that annual bluegrass can usually tolerate ice cover for up to 60 days. After 75 days, it’s basically all dead. Moeller said he has seen ice cover atop poa annua for longer than 60 days, and the turf has fared well. He’s also seen ice on annual bluegrass greens for only two weeks, and the turf has died. He suspects it depends on how the ice forms, how severely it forms, as well as such other issues as the type of fall season, the degree of wetness and sudden drops in temperature. Each variable can alter the general rule of thumb of turf’s length of survival under ice cover.

Bentgrass, on the other hand, can tolerate upwards of 100 days under ice cover.

Moeller said it’s a good idea to periodically monitor what is happening beneath the ice layer. He suggested taking a plug from the epicentre of the green where the ice is thickest and then moving on in concentric circles to get a well-rounded idea of what is happening. Drilling through the ice and pulling plugs from frozen ground is not an easy process, he said, especially when it’s usually an extremely cold day.

Plugs can be incubated on a window sill for about a week. If they look good at that time, it might suggest everything is OK beneath the ice cover and nothing needs to be done. If the plugs appear dead, it might be time to remove the ice immediately because the turf is already weak and is apt to get weaker.

Moeller said less than 1 per cent of the green is being sampled, but taking plugs can provide useful information and provides a better idea about how to manage that snow and ice. He suggested, however, that once a decision is made to remove ice, the superintendent has committed himself to it and he should be prepared to make the most informed decision possible.

Reports of ice cover three to four inches in thickness have been made in some regions of southern Ontario. Moeller said ice that thick cannot be removed in one fell swoop.

“You can do more damage to the turf just from trying to break it up and removing it as opposed to leaving it on there.”

Superintendents will usually break up the ice with an old aerifier, but Moeller suggested breaking it down to only 90 per cent of its cover. If the ice is four inches thick, it should be broken down to about three-quarters of an inch. When attempts are made to break up the entire ice cover, that’s when damage is seen.

Once the ice cover is down to only three-quarters on an inch or an inch, a darkening agent can be applied to encourage melt of the remainder.

“The key is you’ve got to work with the weather.”

During most winters, a thaw lasting about a week comes along, ice is removed and it gradually gets cold again. Without such a thaw this winter, ice was removed and snow was piled on top of greens to provide some insulation. That’s a best case scenario when the winter gets as cold as it did this year, Moeller said.

There are many variables as well as luck involved when it comes to ice removal, he added.

Greens need time to recuperate in the spring if severe winter damage is realized. If courses allow play on severely damaged greens in spring, the surfaces will be all poa. Temporary greens will allow the recovery time necessary, but they also tend to hurt spring revenue. Moeller said although that spring revenue is wanted, it’s most needed in July and August when the majority of play occurs. Temporary greens can ensure that damaged greens have the necessary time to recover in time for increased play in summer.

Moeller warned not to let turf suspected of being dead from winter injury to get dry in the spring because some of that grass might still be hanging on, and a dry stretch could be the final nail in the coffin. He said light and frequent irrigation can be helpful. The timing is also right for seeding. A good seed bed can be created by verticutting in a couple directions, slice seeding or dimple seeding.

“The key is seed to soil contact.”

Time is important because there is no certainty about what turf is dead and what might still be alive. Because the soil is still cold in the spring, a slow-release fertilizer will take longer to work. Putting down black topdressing sand to warm up the soil is a good way to promote turf recovery.

Fertilizing once seeding has been done can be a challenge because one part of a green will require a program different from another part.

Moeller said he saw golf courses in his territory that had greens ranging from 10 per cent dead to 90 per cent. The good turf on the worst greens were transplanted onto greens that suffered little damage while the most affected greens were resodded.

Golf courses equipped with a bentgrass nursery green on the property have an advantage over those without one. Bringing in pure bentgrass sod from off site can be challenging because it’s not accustomed to the golf course’s site or its soils. Sod from an on-site nursery green or a chipping green is the better option.

“It looks great initially, but then it sees some struggles,” Moeller said of bentgrass sod brought in from off site.

Seeding is the preferable option over sodding, however, he added, noting that sodding is practical if an entire green is wiped out.

On the positive, a green which is pure bentgrass is “a heck of a sales tool.” Not only will the green come out of winter better than the others, but it will play a lot better in the summer. Superintendents can use it as a sales tool with their general managers, greens committees and owners to show how advantageous it is to have bentgrass putting surfaces over those grown to annual bluegrass or a mixture of the two.

Moeller said that agronomics must be factored in when deciding when to open a golf course for play in the spring. Revenue is important, he added, but agronomy has to be the primary focus.

It’s vital for superintendents to keep members abreast of what is happening with the golf course, explaining to them why a spring opening has been delayed. Adjustments might also have to be made to aeration dates and the scheduling of tournaments and other outings. If they aren’t adjusted, recovery will be slower and superintendents can expect some form of damage later in the season because it is likely less bentgrass will have germinated.

The more that can be done to help bentgrass germinate, the better, Moeller said.

“Not worrying so much about green speeds this year should be a priority.”

Keeping mowing heights at a reasonable level and not forcing the issue is essential this year. He suggested superintendents could try alternating between mowing and rolling their greens this year. It must be remembered, he added, that golfers at most courses are either mid to high handicappers.

Ball speeds between 9.5 and 10.5 are more than enough this year after such a damaging winter, he said, reminding the club owners and general managers in the audience that there are already enough challenges associated with golf, including pace of play, cost and the stigma that it’s an elitist sport. The game is supposed to be fun to play, he added, noting that three and four-putting saps the fun from it.

If the golf course is set up with the majority of golfers in mind (the mid and high handicappers), it will have a better chance to recover from the winter. Moeller said it’s often the case, however, that the minority of golfers (the low handicappers) who are the loudest and end up getting their way.

Moeller said he’s not against annual bluegrass putting greens, but emphasized it’s a difficult grass to maintain and it’s unreliable. Mixed poa and bentgrass surfaces can be “absolutely awesome.”

Seven of the top 10-ranked golf courses in the United States have annual bluegrass putting greens and, with the exception of Winged Foot Golf Club in Mamaroneck, N.Y., all have extensive tree management programs. Trees which may have presented shade issues in the past have either been removed or pushed back far enough so that they no longer pose a problem.

Moeller reiterated that bentgrass is still the better surface, but warned it will not perform well if it is in constant shade or the greens drain poorly.