The large mechanical devices seen near putting greens, often called turf fans or greens fans, are specialized equipment dedicated to turf management. Their presence addresses specific environmental challenges faced by the highly manicured grass, such as sensitive bentgrass or Poa annua used on greens. These fans are not for cooling golfers, but maintain the health and playability of the turfgrass. By generating air movement, the fans manipulate the microclimate surrounding the grass canopy. This localized air circulation is a proactive measure against physiological and pathogenic stresses that can quickly damage the course’s most important surfaces.
Managing Surface Moisture and Dew
Controlling the moisture level on the grass blades is the primary function of turf fans, directly impacting the turf’s susceptibility to disease. When air is stagnant and humidity is high, moisture remains on the leaf surface for extended periods, a condition known as prolonged leaf wetness. This wetness often results from heavy morning dew or guttation, where the grass plant exudes water droplets overnight.
A consistently wet turf canopy creates an ideal breeding ground for turfgrass pathogens. Fungal diseases such as dollar spot, brown patch, and pythium blight thrive in high-moisture, low-air-movement environments, causing significant damage. The fans increase air velocity across the surface, facilitating the rapid evaporation of surface moisture. This movement reduces the duration of leaf wetness, breaking the disease cycle before fungal spores can germinate. Maintaining an air current of at least 3 to 5 miles per hour across the putting surface is the goal for effective moisture dispersion, lowering the relative humidity within the grass canopy.
Preventing Heat Stress and Turf Burn
Moving air provides a cooling benefit to the turfgrass, protecting it from localized heat stress. On hot days, the grass canopy temperature can be 10 to 15 degrees Fahrenheit higher than the surrounding air. This heat buildup is harmful to cool-season grasses like creeping bentgrass, which perform poorly when soil temperatures exceed 80 degrees Fahrenheit.
The fans assist the grass in its natural cooling process through evapotranspiration. This process is similar to sweating, where the plant releases water vapor through small openings called stomata. When air movement is limited, the air surrounding the leaf becomes saturated, preventing further evaporation. The fans continuously replace this saturated air with drier air, allowing the plant to continue transpiring and effectively cool itself. This cooling effect can lower the canopy temperature by up to 10 degrees Fahrenheit, helping prevent the physiological decline and root death that occur during summer heat.
Design and Strategic Placement
Turf fans are designed to maximize airflow over the turf surface, often mounted on pedestals ten feet or less in height to project air across a wide area. The goal is to generate consistent air speed over the entire green, requiring the fan to be positioned close, ideally no more than 20 feet away. Many modern fans utilize oscillation to distribute the air current over a larger area, replacing older, stationary models.
Strategic placement focuses on microclimates where natural air circulation is restricted. Greens situated in low-lying bowls, surrounded by dense trees, or next to buildings are prime candidates for permanent fan installation. Courses also utilize portable, trailer-mounted fans to target specific areas experiencing temporary stress, such as wet spots or localized hot zones. Fans are run strategically: overnight and into the early morning to disperse dew, and again during the hottest parts of the afternoon for evaporative cooling.