Managing microclimates on golf courses

Dealing with microclimates is nothing new to superintendents, but understanding the science behind them can help with management


La Rinconada Country Club
Three factors that can greatly influence microclimates are obstructions to sunlight and airflow and slope of the land — all of which are apparent here at La Rinconada Country Club in Los Gatos, Calif. Photos by Adam Weidenbach

All golf course managers know that course conditions can vary from hole to hole. Heck, they can even vary in different spots on the same hole. From a scientific point of view, what superintendents are dealing with are microclimates. 

By definition, a microclimate is a small area whose climate varies, sometimes significantly, from its surroundings. For golf courses, the biggest implication of microclimates is how they affect turf conditions.

Kevin Breen, CGCS, director of greens and grounds at La Rinconada Country Club in Los Gatos, Calif., and the current president of GCSAA, notes, “There are differences even within individual greens that affect watering and cultural practices that are needed to provide consistent putting surfaces.” 

Jeff Heaton, the GCSAA Class A superintendent at Lake Geneva (Wis.) Country Club, says, “I would argue that every one of our greens is in its own microclimate, and in some cases, it changes within each green.” 

Dale Bremer, Ph.D., is a retired professor and director of graduate programs in horticulture and natural resources at Kansas State University in Manhattan, Kan. He says turf conditions are affected by “weather elements including solar radiation, air temperature, relative humidity, wind speed, and precipitation.” All of these elements can vary greatly from one part of a golf course to another, thanks to microclimates.

Kevin Breen
Kevin Breen, CGCS, director of greens and grounds at La Rinconada CC — and GCSAA president — has a degree in meteorology, so he’s well versed in the interplay between weather and turf conditions.

Triple trouble

The first question that many have about microclimates is, “Do weather conditions vary on this scale on their own?” Most do not. Sunlight is consistent, only being influenced by large-scale factors. Air movement, or the wind, is pretty much the same, being controlled by large-scale weather systems. Precipitation can vary on this scale, especially convective showers and thunderstorms, but this would be random unless other factors were involved. 

Variations in conditions we see on a golf course are the result of the interaction of weather elements and variations in surface and subsurface factors. 

According to Bremer, three of the most important factors affecting microclimates are “obstructions to sunlight, obstructions to airflow and the slope of the land.” The first two factors are often related, with the obstructions creating shade and/or blocking the wind. 

Heaton, an 11-year member of GCSAA, concurs. “Shade, airflow, soil temp and moisture vary wildly between our greens. After shade, the airflow issues in our microclimates have the most impact on plant health.”

Bremer explains that “shade lowers air temperatures due to a blocking of incoming solar radiation.” Since relative humidity is an inverse function of temperature, shading produces a higher relative humidity. 

With evaporation and evapotranspiration being inversely related to relative humidity, higher humidity means less water loss. This can be good in dry situations, but harmful to turf in moist conditions, even promoting disease.

Shade issues are directly related to the direction and angle of the sun’s rays. Both of these vary during the day and from one day to the next. The sun rises in the east but only due east on the equinoxes. It will rise north of due east in the winter and south of due east in the summer (in the Northern Hemisphere midlatitudes). The sun will be due south at solar noon (not noon local but halfway between sunrise and sunset). Sunsets are similar to sunrises — in the due west only on the equinoxes, north of this in summer and south in winter.

In terms of elevation angle, the sun appears at the horizon at sunrise and remains low in the sky in the early morning. It gets higher in the sky before reaching its zenith at solar noon. It lowers in the sky in the afternoon and goes below the horizon at sunset. Over the course of a year, the sun is highest in the sky on the summer solstice and gets lower each day until the winter solstice, after which it gets sequentially higher. The lower the sun is in the sky, the longer the shadows produced. Shading effects would be maximized daily in the morning and late afternoon and in the evening and seasonally in winter.

As for obstructions to airflow, Bremer says, “Wind mixes the air, and this affects water usage by the turf.” 

Evaporation of surface water and evapotranspiration of subsurface water are functions of the relative humidity of the air. With little or no wind, the layer of air just above the surface will become more saturated with water vapor, and the relative humidity increases. This will slow the process of evaporation. If there is wind, this moist air is constantly replaced with drier air, which accelerates the evaporation process. Therefore, obstructions to airflow or wind have similar effects downwind on the water budget as shading, according to Bremer. They would be good in dry conditions but potentially harmful if excess moisture is present.

Trees at La Rinconada Country Club
Trees, Breen says, are the “most impactful factor … when it comes to problems that arise when producing great turf” at La Rinconada CC.

Tackling trees

Obstructions to sunlight and wind include things like hills or buildings on or near the course. However, on most golf courses, trees are the most common problem.

“Yes, all those factors come into play when dealing with trees,” says Breen, a 32-year GCSAA member who has a degree in meteorology from the University of Nebraska in addition to the horticulture/turf management degree he earned from Colorado State University. “They are the most impactful factor on my course when it comes to problems that arise when producing great turf.” 

Jennifer Torres, the GCSAA Class A superintendent at Westlake Golf and Country Club, Jackson, N.J., and a member of the executive board for the GCSA of New Jersey, agrees. “I absolutely have issues with trees blocking sun, air and roots sucking the life out of soils below,” she says. 

Sean Tully, the GCSAA Class A director of grounds at Meadow Club in Fairfax, Calif., has plenty of experience in removing obstructions to sunlight and air movement as a way to minimize the impact of microclimates.

“One year we removed some trees behind our 10th green,” the 25-year GCSAA member says. “I took some moisture readings before and after and showed a noticeable difference in both temperature and moisture. Fewer trees around the greens and tees will help to get more light and air movement in and around our greens. Tree removal for us has been very beneficial to the greens and tees that were challenged by the shade caused by the trees and by the roots competing with the grass.”

Heaton adds, “Shade and airflow issues caused by topography and trees are the biggest contributors to our microclimates. On our problem greens, the areas that struggle have rich soil, stay in the shade longer than the rest of the green and have consistently higher moisture levels. In extremely wet and warm weather, when we are not able to control standing water on the course, areas with poor airflow will suffer from ‘wet wilt.’ Wet wilt, coupled with mechanical damage, has caused the greatest damage to the golf course. I say airflow again here because I believe these areas would not struggle as much, even in shade with poor soil, if there was decent airflow. In terms of solutions, we have had success with tree removals.”

For Tully, shading creates additional problems in the form of frost that forms on some of his greens but not others. “We have some hills around the course that block a lot of sun during the winter,” he says. “Shade in some areas means we have two greens that hold on to their frost for another 30 minutes past the rest of the greens. One green in particular is at the end of a canyon, and when we have multiple days of mornings with temperatures below 30, the green starts to get frozen in the upper inch or two.”

Torres, a 16-year GCSAA member, has a similar problem. “As for the frost, many greens here are surrounded by trees that shade the sunlight and lengthen the time it takes for frost to melt,” she says. “This causes delays in play and maintenance.”

Trees at Westlake Golf and Country Club

Trees at Westlake Golf and Country Club
At Westlake Golf and Country Club in Jackson, N.J., superintendent Jennifer Torres says, “I absolutely have issues with trees blocking sun, air and roots sucking the life out of soils below.” Photos courtesy of Jennifer Torres

Lay of the land

In terms of topography, the slope of the land is an important factor. Bremer says the direction of the land’s slope is critical in terms of solar radiation exposure. In the Northern Hemisphere midlatitudes, the sun is due south at solar noon when it’s highest in the sky and producing the most effective heating. As a result, Bremer says south-facing slopes will have greater radiation exposure. 

This increases temperatures in comparison to other slope directions or flat ground and will result in more evaporation and evapotranspiration by the turf.  Soils will become drier, and more water is needed for turf maintenance. North-facing slopes will have the opposite effect because solar rays will come in at a greater angle and be less concentrated. Shading can also result. Thus, these areas will be cooler and wetter. 

Breen has seen these effects at his facility in the Bay Area. “South-facing greens tend to heat up more readily and require more attention,” he says. “Moss and algae on shady and north-facing areas is a concern.”

Another concern with sloping terrain is its effects on the water budget. Bremer says, “You will have greater runoff during rain or irrigation depending on the severity of the slope.” Slopes that are more susceptible to prevailing winds will also have more evaporation, meaning they’ll be drier than other areas.

Torres deals with just that on the 11th hole at Westlake G&CC. “That hole has low areas that also stay wet while the high rear of the green tends to dry out. As for hand-watering, there just seems to be those humps and ridges that need that extra TLC that overhead coverage just can’t give them, no matter what system you have.”

In addition to slope, if the actual elevation on the course changes significantly, such as can be the case in mountainous terrain, it can affect temperatures. Temperature normally decreases with height. The reverse happens when we have an inversion as the air temperature increases with height. This is typical on clear, calm nights when the surface radiates heat out into space. Denser cold air will then sink into lower areas. 

Tulley notes, “Our weather station is at the lowest elevation on our property, so our temps tend to be colder than the rest of the course. Wind speed is less as the station is a bit more protected.” Even relatively minor elevation changes can see this effect. This is a concern if the air temperature at the surface drops below freezing, allowing for potentially damaging frost. 

Below the surface, besides the above factors, soil characteristics are crucial. Of course, the type of turf being used is also critical in terms of its environmental requirements. 

Jennifer Torres at work on the golf course
Torres says cultural practices like the use of a TerraSpike aerifier, help her and her crew manage finicky soils.

With plants deriving their water from the soil, Bremer says, “Beyond soil depth, soil texture is very important. Silt loam soils hold more water than sandy soils, so plants in sandy soils dry out faster without frequent irrigation or rainfall. And while clay soils technically hold more water than silt loam soils, the water in silt loam soils is generally more available to the plant. Compaction of soils (e.g., from traffic, especially in silt loam or clay soils) also restricts rooting and plant-available water.”

Torres deals with that problem. “With the soils at Westlake, we are experiencing excessive drought stress during drier periods,” she says. “The soils will seal off if not kept moist enough. Now with the new system, we can manage it better along with cultural practices like the Terra Spike machine that not only goes down into the profile but also kicks back and fractures the soil, allowing air and water to penetrate more.” 

Heaton has a different issue with soil moisture. 

“Greens with more shade and poor airflow will have warmer soil temperatures, especially when there is a high percentage of native soil in the profile,” he says. “That could be due in part to the amount of microbial activity in these rich soils. On our problem greens, the areas that struggle have rich soil, stay in the shade longer than the rest of the green and have consistently higher moisture levels. Areas of the green that have less shade and sandier soil stay drier and struggle less.”

Ed Brotak, Ph.D., was a longtime professor of atmospheric sciences at the University of North Carolina, Asheville.