How to keep the course in play during cold spells

Alistair Dunsmuir
By Alistair Dunsmuir October 30, 2011 14:10

How to keep the course in play during cold spells

In the UK there are generally few issues with golf being played in winter other than the constraints placed upon us by the variable (or terrible, dependant on your viewpoint and location) British weather. These now usually relate to conditions created by excess winter rainfall, flooded and saturated play surfaces normally being accepted by golfers as unplayable. However when temperatures drop and frost forms there is always pressure to get play underway even when there are good reasons why this should not be the case. This article outlines the concepts associated with play and agronomic matters during periods of low temperatures and frost.

Frost – more or less

In the UK, the predictive number of frost days varies enormously, due to the influence of sea temperature, wind direction, altitude, exposure and so on. Although climate change due to global warming would lead us to believe that there are now likely to be significantly fewer days when frost occurs, there is little to indicate a long-term trend over the 20th Century.

The coldest day in the climatic record is as far back in time as January 20, 1838 (mean temperature -11.9oC). However, the mean number of ‘cold days’ (mean temperature of <0oC) for the long term 20th Century record is 11.5 days (Hume: Air Temperature in Central England) per annum. Between 1940 and 1970 the number of cold days was generally above this average, with a peak of 57 in the winter of 1962/3. However the early parts of the 20th Century had comparably few and until 2002 four winters have occurred when there were no recorded cold days at all; 1922/3, 1924/5 and recently 1974/5 and 1997/8. Records for the period 1993-2002 also show an average of approximately six days, although generally since 1998, cold days are well below average values. This would indicate that the requirement for protection measures may well be reducing, however there will be times when an understanding of cold and frost impact on grassed surfaces will still be required.

Frost – what is it?

For agronomic purposes, all frost is classed as an abiotic plant disorder and although there are wide ranging differences in effect and longevity, all have the potential to cause damage to directly or indirectly to plants.

White or ‘hoar’ frost

This is common in the UK and occurs when (initially small) surfaces are cooled by nocturnal radiation. This usually occurs when there is no cloud cover, allowing heat to radiate away from the ground. Once the air temperature drops below the dewpoint of the air next to the surface, water in the air condenses and ice crystals begin to form on the surface of the grass plants leaves. Turf so affected will appear white and the outermost cells of each leaf will begin to freeze as the temperature at the interface with the ice drops. If traffic (feet, trollies and so on) are then allowed onto the frosted surface, cells that are frozen can rupture causing physical and physiological damage to the grass plants. The most common result of this is the subsequent burnt or discoloured appearance of footprinted or trafficked areas. These are initially blackened or grey in appearance but become yellowed as damaged tissue dies. Recovery is dependant on the amount of damage caused and subsequent growth rates. It should be noted that constantly trafficked areas in winter, when there is little or no recovery, may show loss of density, uniformity and increased disease susceptibility as well as poor recovery when temperatures rise and growth reinitiates the following spring.

Permafrost or ‘black’ frost

This can either occur over a period of time, initially starting with the same white frost, with freezing continuing as temperatures continue to drop, or initially in response to a quick and substantial temperature drop and lower humidity, which freezes the leaves of the plant directly. Although true permafrost is more of a geographical and geological feature, periods when soil and air temperatures are below freezing will produce this as a generally short-lived effect in a UK winter. Although usually not as visible as white frost, use of play surfaces can cause extreme injury to the plant. This can be physical damage to cell walls and so on caused by direct injury and/or damage to the internal parts of the plant due to ice crystal formation and subsequent impact from traffic.

Other factors

It should also be noted that ‘direct low temperature injury’, although not common in the UK, can be caused to the crown of the plant (the part of the plant responsible for shoot and root growth) during extended periods of cold weather, leading in the worst case to eventual death of the plant. Damage is typically associated with inadequate water availability within plant tissue. Symptoms are normally a bronze or brown discolouration, usually beginning on the leaf tips but occasionally seen on complete plants. Plants so affected are often not noticed until weather conditions improve, temperatures rise, growth reinitiates and the affected area fails to ‘green up’.

A more common winter problem in the UK is desiccation, which can happen during dry, cold periods. Often cold, windy conditions, low humidity and high solar radiation (bright, sunny days) produce conditions that are favourable for desiccation, or drying out, of the plant tissue. Once the plant, even in the state of partial dormancy, becomes desiccated, it can stop growing and die, although this is rare in the UK. General exposure and topography of the local environment will normally influence this effect markedly.

Thawing

As temperatures rise following periods of frost, there will inevitably be a thaw. This occurs initially at the plant/soil interface, ice crystals on the surface of the leaves melting first followed by ice within the plant cells. Plants at this time may be notably flaccid or soft (possibly due to hydration issues and so on) and are at risk of direct injury from traffic. As the upper soil profile begins to thaw, this introduces a further set of problems associated with possible saturation. The thawing ice from the plants above coupled with the thawing ice in the profile lying above a still frozen mid profile leaves a perched water table in place. This can result in local flooding and soil instability and areas so affected will have plants at severe risk of injury to leaf, crown and roots due to any traffic impact. In addition, loss of surface levels and stability to playing surfaces so affected can occur.

Snow cover

Light coverings of snow will do little damage to grass plants. However brushing snow from, say, the line of a putt, can cause injury to plants. Heavy snow should normally stop play anyway and any long term cover generally acts as an insulator. Thawing snow requires the application of the same principles as thawing ice.

Management options for play

The decision as to whether play should be allowed on the course should be left to the course superintendent or course manager. They are experienced professionals and know how to balance the requirement for play with the long term health and condition of the course and its play surfaces and the requirement for revenue production.

Scenarios

With short-lived white frost (say no more than an hour), although there may be some ‘footprinting’, play will usually not create many issues. However if frost has been in place overnight, inspection will be required. This usually allows a decision to be made on an ‘opening time’ for the general play, however even in late spring when temperatures can rise quickly, this may be as late as mid morning. Greens with compromised microclimates, such as those that are shaded and/or alongside water, may require longer to recover for play and may be restricted for use during colder periods. Checking weather reports can allow two pin positions to be cut in advance, keeping one towards the greens front or on a frost temporary.

Note: As a general rule, winter pin positions should be varied as much as possible around greens’ surfaces to avoid concentrating wear and tear. Remember to use those corners and don’t be put off by placements close to the edge of a green or near a hazard.

Long-term freezing

As a general rule, the more play that takes place during extended periods of low temperatures, the greater the levels of damage, the longer it takes for full recovery and the more work that is required by greenkeeping staff to repair areas of greatest wear. Temporary/frost greens are mandatory until the thaw and conditions subsequently improve.

Thawing

Unless air and soil temperatures remain below freezing and the soil profile has remained frozen for this time, any rise in air temperature, particularly at the surface, can lead to a ‘thaw/refreeze’ cycle. This can be extremely damaging anyway, however standing water from thawing ice, saturated profiles and so on may require complete course closure to prevent damage.

Freezing effects on different grass species

Cool Season (C3) grasses are generally tolerant of cold conditions. Most can alter their morphology and physiology to deal with low temperatures and this usually occurs during an acclimatisation period in autumn, when there is a downward trend in temperature. This helps the plant to maximise winter hardiness by producing changes in the way the plant functions and includes reducing plant water potential to prevent freeze injury and also increasing fatty acids to help with plant membranes and cell walls. However, as noted above, even this does not protect them fully, and, as noted, freeze/thaw cycles may in fact increase risk, particularly if there is a sudden temperature drop following a period of warm weather, something that appears more common now than previously.

Bentgrass and fescues are generally tolerant of cold conditions. Annual meadowgrass (Poa annua) is variable, as would be expected, and may also lose colour. However, recovery usually follows due to adaptation of individual subspecies and regeneration from the seed bank.

Perennial ryegrass (Lolium perenne) can be somewhat variable under cold stress although modern cultivars appear better.

Conclusions

Regardless of course type, age and species composition, it will from time to time be a requirement to protect play surfaces that are freezing, are frozen and are affected by low temperatures. Management of this scenario is still not a common requirement in the UK, but it is still important and particularly so when tied in with general winter protection measures.

Every course will have its own set of limitations, for instance smaller sites have more concentrated traffic and similarly smaller greens have less buffering capacity when it comes to play. However continued play on surfaces that are compromised by frost, particularly at a time of year when re-growth and recovery are poor or non-existent, will inevitably result in some form of unrecoverable damage.

This in turn will likely continue to compromise general appearance and playability of the affected surface/surfaces until the greens’ staff can begin renovation work, normally in the following spring.

This is also likely to have budgetary and resource implications, all of which could have been avoided by avoiding damage in the first place.

However there will inevitably be differences in management of cold conditions as priorities are often different from golf club to golf club. Proprietary and pay and play courses are more inclined to accept some damage while keeping play and therefore revenue flowing. However members’ clubs often express the importance of having the course in the best condition possible coming out of winter and into the playing season. This inevitably means that some measures are kept in place during winter to help protect of the course.

Inevitably frost greens, temporary tees, play mats, traffic management schemes, ropes, lines, limited trolley use and so on are often unpopular with members, however, the increased use of golf courses during the winter months means that from time to time it makes sense to put measures in place to protect the course from damage that may remain in place for some time the following spring. Remember also the cost and resource implications in repairing damaged areas and that these can and do look ‘untidy’ until fully recovered.

Alistair Dunsmuir
By Alistair Dunsmuir October 30, 2011 14:10
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