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Key Takeaways

  • Syringing is applying water to wet the leaf surface, not to replenish soil moisture. 

  • The principle benefits of this practice are cooling the plant and preventing wilt.

  • The impact of syringing alone on soil and canopy temperatures is typically small and short-lived. 

  • Syringing in conjunction with the use of aboveground fans has more-significant cooling effects.

  • Given the limited benefits of syringing, proactive steps to reduce the risk of heat and moisture stress should be prioritized.

     

When you hear someone talk about “syringing” putting greens, what does that mean to you? While the term syringing may be common, people’s definition of it is far from clear or consistent. Some think of it as applying a light, superficial mist of water, while others view it more like hand watering with the goal of slightly increasing soil moisture. Along with varying definitions, there are also differing opinions about the potential benefits and drawbacks of syringing.

This article will take a deep dive into this shallowest of watering practices to examine what syringing is and how it works (or doesn’t), along with implications and additional considerations for water management on putting greens. We will start with the principles and theory behind syringing, then see what turfgrass research has to tell us about its effectiveness, and finally bring it all together with some practical recommendations.

Defining Syringing

Simply put, syringing is about wetting the surface, not the soil. If you’re looking for a more formal definition, you can visit Michigan State’s Turfgrass Information Center website, a great starting point for investigating any turfgrass topic. There, you’ll find the classical description of syringing as: “The spraying of turf with small amounts of water with the objective being to (i) dissipate accumulated energy and cool the leaves by evaporating free surface water, (ii) prevent or correct a leaf water deficit, particularly wilt, and (iii) remove dew, frost and/or exudates from the turf surface, usually in the post-dawn period,” (Beard & Beard, 2005). In this article, we will set aside that third part about removing dew, frost and exudates, and focus on the first two objectives: cooling leaves and addressing wilt.

What you don’t hear in that definition is any mention of replenishing soil moisture. In other words, the benefits of syringing are supposed to come through wetting the turfgrass surface only. So, how exactly does that work?

Principles of Syringing

Let’s start with that first syringing objective: cooling turfgrass leaves as water evaporates from their surface. This cooling effect comes from the fact that it takes a great deal of energy (heat) to break the bonds between water molecules and transform liquid water into water vapor. On a hot day, when a syringing application coats turfgrass leaves with a light layer of water, that water can absorb heat from the leaves and from the air. As heat is transferred from the leaves to the water, leaf temperature decreases. Eventually, water droplets absorb enough heat to become water vapor, carrying that absorbed heat away from the plant and into the atmosphere.

Moving on to the second syringing objective: preventing or correcting water deficit and wilt. Here we need to appreciate how water moves through the environment, and the key concept is the “soil-plant-atmosphere continuum.” Specifically, we’re talking about how water in the soil moves up through the plant and exits (transpires) into the atmosphere. Similar to the evaporation of water from the leaf surface, transpiration has a cooling effect on the plant. This upward water movement is driven by the fact that generally, the atmosphere is relatively dry compared to turfgrass leaf tissue.

Turgidity describes the way healthy turfgrass leaves maintain their shape and orientation because of the abundant water within their cells. The other side of that coin is wilt, where leaves lack sufficient water to maintain their orientation or shape, as evidenced by the all-too-familiar footprints seen in stressed areas on a hot day. This tug of war between turgidity and wilt follows the natural process known as homeostasis, where organisms try to maintain internal stability by seeking equilibrium with their external surroundings. In this situation, water moves from areas of relatively higher concentration (inside plant tissue) to areas of relatively lower concentration (the atmosphere). As this process plays out on hot, dry and/or windy days, if water exiting plant leaves cannot be replaced by root uptake from the soil, turfgrass begins to wilt.

Syringing is intended to slow down this exodus of water by masking the fact that the air outside the leaf is much drier than the cells inside the leaf. Applying a light amount of water to the turf surface affects the water content of the immediately surrounding air, a narrow region known as the “boundary layer.” Elevating the humidity of the boundary layer effectively slows down transpiration by reducing the external atmospheric demand on water inside the plant, and by extension, water in the rootzone.

So, at this point we’ve defined what syringing is and how it works in theory, but how effective is syringing on an actual putting green?

What Turfgrass Research Says About Syringing

This is the point where I will tell you that we don’t have as much research on syringing as we might like. However, there are some valuable takeaways from the results that we do have. A theme running throughout turfgrass research is that while syringing is a tactic for cooling putting greens, it is by no means the only tactic, and the practice is often studied in combination with air movement.

One of the foundational turfgrass research studies involving syringing comes from Michigan State in the late 1960s, where ‘Toronto’ creeping bentgrass (Agrostis stolonifera L.) plots were syringed at noon with 0.25 inches of water and temperatures recorded every half hour for both the mat layer and at a 2-inch depth (Duff & Beard, 1966). For half of the plots, air movement was restricted (0 mph), and for the other half, air movement of 4 mph was created. Within each airflow regime, temperature reductions from syringing were relatively small (ranging from 1 to 4 degrees F), with both the mat layer and the rootzone returning to their pre-syringe temperatures after two hours.

While this study is often included when discussing the potential benefits of syringing, there are a couple of caveats worth pointing out. First, the 0.25 inches of water applied is more than what we’ve defined as syringing in this article. Also, applications were made when air temperatures were 75 degrees F. Nowadays, how many superintendents would feel the need to syringe greens with a quarter inch of water during the middle of a 75-degree day? I ask that question not to disparage this research, but to point out how turfgrass management has evolved over the last half century, and also to make a larger point that is important any time we interpret turfgrass research. Research trials are intended to be particular examples that hopefully demonstrate evidence toward a larger truth, but we have to appreciate that their results are a function of the specific circumstances and conditions under which the work was conducted. In other words, when thinking about how research results might apply to your golf course, it is critical to acknowledge how the study is both similar to, and different from, your own situation.

Fast forward to 1981-82 where a two-part research trial compared different syringing volumes and timings on ‘Penncross’ creeping bentgrass greens in North Carolina (DiPaola, 1984). Greens were mowed every other day at 0.250 inches and air temperatures ranged from 75 to 93 F. Here, the cooling effects of syringing were considerably shorter than the two hours previously reported in Michigan. In study 1, seven different volumes of water ranging from 0.002 to 0.22 inches were applied at either 11:00 a.m. or 1:00 p.m. None of these amounts significantly reduced canopy temperatures one hour after application. On four of the 15 dates, syringing amounts of 0.06 inches or greater significantly reduced canopy temperatures 30 minutes after application by an average of 1.3 degrees, with maximum reduction of 3 degrees. In study 2, across nine different application timings, including single and multiple applications per day, temperature reductions were typically less than 1.8 degrees F. A couple of important differences between this research and the earlier work are that the water quantities applied better align with our definition of syringing, and that canopy temperature rather than soil temperature is the primary metric being reported. The second point begs the question – with a syringing application, what does success look like? Is the goal of syringing to reduce canopy or soil temperatures, or both? While altering canopy temperatures may be the easier metric to affect and measure, the consequences of elevated soil temperatures on turfgrass root health should not be overlooked, an idea that we will follow through our final research case study and into our recommendations. Ultimately, this research concluded that in the absence of wilt, beneficial effects from syringing are relatively small and short-lived, and the practice as a whole may need to be reconsidered in light of the water and labor required. That phrase, “in the absence of wilt,” is important in its own right because it highlights the fact that controlled experiments are often better equipped to investigate the syringing objective of reducing temperature, and that data specifically focused on wilt is harder to come by.

In 2000-2001, a study at Auburn University investigated syringing and aboveground fans (used independently and in combination with each other) for cooling a native soil ‘Crenshaw’ creeping bentgrass putting green in Alabama (Guertal et al., 2005). Syringing amounts of 0.05 inches were applied three times per day (noon, 2:00 p.m. and 4:00 p.m.) once air temperatures consistently reached 84 to 90 F, including 35 days above 90 F, with a maximum air temperature of 99 F. In this research, syringing plus fans provided significantly greater reductions in maximum soil temperatures at a 0.5-inch depth than syringing only, or fans only. Interestingly, syringing alone ranked third in terms of reducing temperature, also behind fans only. In other words, if the goal is to effectively reduce soil temperatures, syringing needs to be used in conjunction with fans, if used at all. This research also reported that syringing plus fans reduced the amount of time bentgrass was exposed to stress-inducing temperatures (greater than 81 F), and that on multiple dates, syringing alone actually resulted in lower root-length density, compared to no syringing. Another study from Clemson University reinforced the message that light moisture in combination with aboveground fans was an effective strategy for reducing canopy, soil surface and soil temperatures, further adding that subsurface air movement did not enhance these cooling effects (Rodriguez et al., 2005). The takeaway here is that aboveground air movement is critical for realizing benefits from syringing when it comes to reducing temperatures, both above and below ground.  

"The takeaway here is that aboveground air movement is critical for realizing benefits from syringing when it comes to reducing temperatures, both above and below ground."

At this point, it would be fair to say that in the absence of wilt, syringing as a standalone practice leaves something to be desired for providing appreciable cooling, and that surface air movement plays an important role in whatever benefits syringing does have to offer. As we shift from research to recommendations, the question becomes: If the benefits of syringing are limited, what are the other levers we can pull for managing heat stress on putting greens?

Recommendations

Looking back at the definition, syringing is essentially described as a “rescue treatment” for reducing both heat and moisture stress. From a management perspective, the ideal scenario would be taking proactive steps to reduce the need for rescue in the first place. To help us navigate different management options, we need to bring back the concept of the soil-plant-atmosphere continuum and the common thread connecting those three components: transpiration. Let’s work our way from the bottom up, starting with the soil.

Soil

Independent of syringing, transpiration creates its own cooling effect as water is pulled from the soil, through the plant and released from the leaves into the atmosphere. Plant available water in the rootzone is the reservoir from which this entire process operates. Tracking rootzone volumetric water content (VWC) using soil moisture sensors (SMS) helps inform irrigation scheduling to adequately replenish this reservoir without wastefully exceeding the necessary capacity. Getting the most out of SMS data means developing your own site-specific irrigation thresholds in terms of percent VWC. By determining the VWC values where early signs of wilt first appear, you will create consistent, actionable thresholds for overhead irrigation or hand watering that can be easily communicated. While not yet as prevalent in turfgrass management, matric potential sensors can offer even more powerful insights into how accessible soil moisture is to plant roots. This information is not available through VWC measurement alone.

Plant

While transpiration is common across all turfgrasses, the rate at which it happens can differ considerably among different species and cultivars, and across different locations and maintenance practices (Braun et al., 2022). The syringing research highlighted in this article all took place on creeping bentgrass, a species susceptible to summer bentgrass decline, which involves reductions in root mass. Annual bluegrass (Poa annua, L.) roots may be shorter and even more vulnerable to start with than creeping bentgrass, and likewise experience heat-related reductions (Lyons et al., 2011). Practically speaking, using a soil profiler to visually assess rooting depth can work hand in hand with portable SMS readings of VWC within the actual rootzone as root lengths fluctuate throughout the year.

Another strategy for mitigating summer bentgrass decline is to reduce nighttime soil temperatures. Research at Rutgers University showed that reducing nighttime soil temperature had a greater effect on turfgrass quality and root growth than daytime temperature reduction (Xu et al., 2003). When considering how to create lasting temperature reductions, the overnight use of fans makes sense. In the absence of solar radiation, airflow created by fans allows soils to release more heat into the air. Overnight use of fans offers a nondisruptive tactic for alleviating high soil temperatures to promote turfgrass growth during periods of heat stress. At the risk of stating the obvious, fans are not the only way to improve airflow around greens. Opening up the surrounding spaces by removing detrimental trees and shrubs may provide the dual benefits of increased natural airflow and increased sunlight.  

"Overnight use of fans offers a nondisruptive tactic for alleviating high soil temperatures to promote turfgrass growth during periods of heat stress."

One final plant-related strategy that goes well beyond routine maintenance practices is converting to a more stress-tolerant cultivar or even making the switch from cool-season to warm-season turfgrass species in areas where this is an option. This is by no means a universal solution, but when and where possible, conversion offers a large-scale and long-term approach to managing heat and moisture stress on putting greens. Any turfgrass conversion decision needs to carefully consider a number of site-specific factors that extend well beyond the scope of this article. The grassing strategies chapter of the USGA Water Conservation Playbook is an excellent resource for those interested in exploring turf conversion in greater detail.

Atmosphere

Closely tracking evapotranspiration (ET) is the key to understanding the atmospheric demand exerted on turfgrass moisture status each day. Both historical and forecasted ET data can be used to schedule irrigation and can be obtained from different sources such as the National Weather Service Forecast Reference Evapotranspiration (FRET) website, state or local weather networks, or the USGA’s DEACON® management system. On-site weather stations can provide site-specific ET data, and multiple stations can be used to account for different microclimates on a golf course.

It is important to remember that ET is only a starting point, and that adjustments need to be made when it comes to how much irrigation to apply. Simply put, the goal should be to ensure that there is enough moisture available in the rootzone each day to exceed the demand for how much will be transpired (lost) to the atmosphere. The site-specific irrigation scheduling chapter of the Water Conservation Playbook offers a valuable resource for those looking to make more-precise irrigation decisions using ET (and SMS) to avoid wilt and ultimately reduce the need for syringing.

Finally, as noted earlier, canopy temperature is often used to determine the need for and impact of syringing. Infrared thermometers are a common tool for measuring surface temperature and thermal cameras are increasingly used to visualize temperatures across turfgrass surfaces. While the images they produce can be captivating, it is important to appreciate that thermal cameras are not all the same in terms of how they represent canopy temperatures. In order to obtain absolute temperature values, a (generally more expensive) radiometric thermal camera is required. Within a radiometric image, each individual pixel has its own temperature value. In other words, you can know the exact temperature of each location within that image. A non-radiometric camera simply displays relative differences in temperature across the entire image, not absolute temperature values. When these relative differences are translated to a color-coded scale, the hottest and coldest areas of the image occupy the extremes of the color scale, with everything else falling somewhere in between.

What this means in a practical sense is that in a non-radiometric image, it matters what else is in the image. If a shaded area of rough is in the background, then greens may look excessively hot by comparison even if the actual putting green temperature is not extreme. Similarly, if a hot cart path is in the image, then greens may look relatively cool by comparison even though absolute temperatures may be approaching an undesirable level. The take-home message is that just like turfgrass research, understanding the limitations of technology is essential for getting the most out of it.

Conclusions

Ideally, golf course irrigation is performed with the goal of making every drop count. Along with that, golf course superintendents want to make every minute count when it comes to staff time. Water and labor were interchangeable as the top two current and future concerns for the golf course maintenance industry in a recent USGA survey of industry professionals and experts (Merrick, 2025). When dedicating the critical resources of water and time toward the practice of syringing, it is important to ask: What is the return on that investment, and are there more efficient and effective ways to manage heat and moisture stress?

Collectively, research has shown that the return on investment for syringing as a stand-alone practice is relatively small and short-lived. Incorporating air movement through the use of aboveground fans is a key driver in cooling putting greens, with or without syringing, and making informed irrigation decisions will proactively help greens handle stressful conditions. Ultimately, syringing may be necessary at times, but reducing the need for it whenever possible is a worthwhile and realistic goal.

"Collectively, research has shown that the return on investment for syringing as a stand-alone practice is relatively small and short-lived."

References

Beard, J.B., & Beard, H.J. (2005). Syringing. In Beard’s turfgrass encyclopedia for golf courses, grounds, lawns, sports fields (p. 453). Michigan State University Press.  

Braun, R.C., Bremer, D.J., Ebdon, J.S., Fry, J.D., & Patton, A.J. (2022). Review of cool‐season turfgrass water use and requirements: I. Evapotranspiration and responses to deficit irrigation. Crop Science, 62(5), 1661-1684.

DiPaola, J.M. (1984). Syringing effects on the canopy temperatures of bentgrass greens 1. Agronomy Journal, 76(6), 951-953.

Duff, D.T., & Beard, J.B. (1966). Effects of air movement and syringing on the microclimate of bentgrass turf. Agronomy Journal, 58(5), 495-497.

Guertal, E.A., van Santen, E., & Han, D.Y. (2005). Fan and syringe application for cooling bentgrass greens. Crop science, 45(1), 245-250.

Lyons, E.M., Landschoot, P.J., & Huff, D.R. (2011). Root distribution and tiller densities of creeping bentgrass cultivars and greens-type annual bluegrass cultivars in a putting green. HortScience, 46(10), 1411-1417.

Merrick, B. (2025). A survey of current and future challenges facing the golf course maintenance industry. USGA Green Section Record, 63(02).

Rodriguez, I.R., McCarty, L.B., & Toler, J.E. (2005). Effects of misting and subsurface air movement on bentgrass putting greens. Agronomy Journal, 97(5), 1438-1442.

Xu, Q., Huang, B., & Wang, Z. (2003). Differential effects of lower day and night soil temperatures on shoot and root growth of creeping bentgrass. HortScience, 38(3), 449-454.