By Dr. Leon T. Lucas

CGA Agronomist

Posted: 2/7/2003

All winter, golfers in the Carolinas are familiar with the problem of a "frost delay" at our courses. It creates quite a scene played over and over again: golfers fidgeting away in the golf shop or snack bar waiting for "the word" from the superintendent. Most golfers know that waiting for frost to melt is important to the good health of our turf because walking on frozen grass kills grass blades.

The technical explanation is relatively simple: foot pressure on a frosty grass blade causes some of the ice crystals in the frost to puncture the grass cells, killing the blades. This damage becomes evident over a few days as brown patches, in the shape of footprints, make their appearance. On a putting green, more damage will occur near the hole location because that is the heaviest traffic area on the green. The damage remains into the spring because the affected grass blades are dead and must be replaced by healthy and growing grass.

Playing on frozen soil also damages greens. The plants can be bruised from foot pressure against a hard and frozen surface. The visible damage on frozen soil is less immediate than when frost is present.

What happens? The most severe damage occurs when the top layer of soil thaws on top of a hard, frozen layer. The top layer becomes saturated with water, and depressions from footprints can develop in the softened soil. This makes the putting surface uneven and can take months to smooth or heal.Damage from this situation is not visible at first because the turf roots are sheared at the line between the thawed and frozen soil in the footprints. The turf will move within the thawed layer but not in the frozen soil below. Come spring and even into the summer months, damage created by root shearing often appears as weaker turf while the affected area grows new roots.

What's important here? I know it is difficult to stay off a course on a relatively warm winter day, especially following a long cold snap. But it can be the best thing for your course's spring and summer turf condition.A cold weather snap - temperatures constantly below 25 degrees for several days - can damage or even kill bermudagrass. When this happens, we should expect to see some "winter kill" in the "spring" on our courses. This is particularly true in areas on courses with winter shade or in low wet areas. Cart traffic on weakened turf can cause even more damage.Courses with a lot of shade can expect more winter kill on the north side of trees because the soil in these areas remains colder for longer periods.

Proof of this is how long snow will last in these same areas after a winter storm. Sunlight heat just can't get to these shady areas.

Cold damage in these areas might not be evident to the golfer until the bermudagrass begins to grow again in the spring. Symptoms are easy to spot after the fact - weak or dead bermudagrass that lasts through the spring and even into the summer.

A course superintendent and his staff can determine if cold damage has occurred by collecting plugs from potentially affected areas and placing them in a warmer environment. Identifying early on if this grass is dead or alive helps to determine what management practices will be necessary to grow healthy bermudagrass in the spring and summer.

Extreme cold damage, as has occurred in the Carolinas Piedmont in years past, can result in closing a course during the summer months in order to plant sprigs or install new sod. Early detection of cold damage can help a club and its superintendent plan for the coming months, including the budgeting for repairs...before the damage is even evident.

Winter damage to bermudagrass is less evident on courses overseeded with winter grasses and can be disguised on tees, fairways and greens until mid summer. The overseeded grasses, usually unaffected by cold damage, may grow well and healthy through late spring, masking a problem that will become evident only in the summer.

Options? One drastic alternative is to remove the overseeded grass chemically in late spring. This also eliminates competition for the bermudagrass when its growing season begins. This option allows a superintendent to determine if the remaining live bermudagrass can provide good coverage by mid summer...or if areas will need replanting or resodding.

Another option is to extend the life of the overseeded grass as long as possible into the summer months, giving players a better playing surface during the spring and early summer. The trade off here - poorer turf while new bermudagrass grows in the heat of the summer - has to be weighed. Bermudagrass grows quickly in summer heat. On the other hand, bermudagrass competing with overseeded grasses is weakened in early summer by the winter grass. More cold damage can occur on the shorter cut of bermudagrass greens. Shorter grass has less plant material (shorter roots and fewer stolons and rhizomes). This results in fewer food reserves for spring growth. Further hurting the situation - the soil on greens gets colder because it has less insulation than taller bermudagrass.

You might wonder why a superintendent will irrigate brown or dormant bermudagrass during cold, dry and windy weather. Desiccation (a drying out process) can occur and add to cold damage or cause yet other kinds of winter kill. Desiccation damage is more evident, usually, on higher and drier areas of a course. In this case, the bermudagrass is alive but dormant. Yet the roots, if still alive, are not able to take up enough water from cold soil. Moisture is needed to keep the tissues alive to grow even more in warmer weather.

A superintendent throws yet another factor into his winter decision-making mix. Before early March, he must decide what kind of herbicide to use on bermudagrass to prevent summer weeds. If the "super" anticipates cold damage, he could decide not to use a root-inhibiting pre-emergent type herbicide (usually applied in March) because it also will inhibit root growth of bermudagrass that is damaged by cold weather. Selecting other types of chemicals for weed control at that time can help hasten the recovery of bermudagrass from winter damage and prevent poorer quality turf for months or into the following year. We all hope that severe winter damage has not and will not occur this year. Because of the sometimes significant and long-reaching affects of this problem, it is best for a superintendent and his club to start thinking during the winter months about potential damage.

More information about damage from frost and cold and about the problems associated with overseeding with winter grasses is available in the Turf Notes under the CGA Agronomy Section of the CGA web page (www.thecga.org).