skip to main content

Key Takeaways

  • Growing environments must be optimized for creeping bentgrass putting greens to perform at a high level.
  • Agronomic programs must be structured to promote the strengths of creeping bentgrass and protect against its weaknesses.
  • The lateral growth habit of creeping bentgrass requires management to avoid negative impacts on ball roll.
  • Bentgrass is less tolerant of traffic than Poa annua, which has implications for the frequency, intensity and timing of mowing, aeration, grooming and many other putting green management practices.
  • Data collection can be used to analyze how creeping bentgrass putting greens are performing as well as to communicate more effectively with golfers and stakeholders.
     

Putting greens are without question the most important playing surfaces at any golf course and their condition plays a key role in golfer satisfaction. Bad greens will almost certainly mean unhappy golfers. In locations where cool-season grasses are the best option for putting greens, Poa annua, creeping bentgrass, or a combination of the two, likely make up the putting surfaces. Previous Green Section Record articles took an in-depth look at managing Poa annua putting greens and managing greens that are a mix of Poa annua and creeping bentgrass. This time, we’ll take a deep dive into the ins and outs of managing creeping bentgrass putting greens.

When compared to Poa annua, it is well documented that creeping bentgrass has better heat tolerance, holds up better to drought, is less susceptible to winter injury, and is more resistant to many diseases. This is especially true when looking at creeping bentgrass varieties that have come out of plant breeding programs in recent years.

However, bentgrass does have its shortcomings. For creeping bentgrass putting greens to deliver quality and consistent playing conditions, growing environments must be optimized and the agronomic program must be structured to leverage the strengths of this grass while accounting for its weaknesses.

Optimizing Growing Environments

Failing to create proper growing environments around creeping bentgrass putting greens is a surefire way to jeopardize turf health, which will have a negative impact on playing conditions. Furthermore, growing environments must be monitored and maintained because detrimental changes can gradually occur over the years.

A shaded environment is not ideal for maintaining high-quality creeping bentgrass putting greens. Direct sunlight is critical for driving photosynthesis so the turf can produce carbohydrates used for energy. USGA-funded research conducted at the University of Arkansas determined the minimum amount of sunlight needed – reported as the daily light integral (DLI) – to maintain creeping bentgrass putting greens in acceptable condition was a DLI of 30 (Russell et al., 2018). Many northern areas where creeping bentgrass greens are grown may only average a summertime DLI of around 35 to 40, so even a slight reduction in the amount of light reaching the green can result in unacceptable turf quality. Moreover, direct sunlight first thing in the morning has the added benefit of accelerating the rate at which moisture evaporates from the leaf surface and helps reduce disease pressure. Shaded environments will not only lead to poor bentgrass conditions, they also encourage Poa annua encroachment since it has a much lower DLI requirement. Annual bluegrass has been found to survive and even reproduce at a DLI below 10 (Yasin et al., 2017). If you’re trying to keep Poa annua out of your bentgrass greens, sunlight is a key part of the equation.

To improve growing environments around creeping bentgrass greens, tree removals should be focused on increasing the amount of direct sunlight that reaches the putting green in the morning through the midafternoon. Trees located to the south and east of putting greens should be prioritized for removal since their absence will allow sunlight to reach the putting greens when carbohydrate production is at its peak.

Trees should also be removed if they block the prevailing wind. The importance of air movement to help bentgrass regulate its temperature during the most stressful portion of the golf season cannot be overstated. If tree removals cannot be performed, or if air movement is restricted by objects that cannot be removed, fans should be installed to create air movement. 

Proper drainage is just as important as adequate sunlight and air movement. Ideally, putting greens are contoured in such a way that water does not pond in low areas. From an internal drainage perspective, an outlet should be provided within the putting green profile so excess water is removed when field capacity is achieved. Without proper drainage, creeping bentgrass is more susceptible to thinning out under saturated conditions. Poor drainage also increases disease pressure on bentgrass, especially pythium diseases. Stakeholders often decide to rebuild native soil putting greens to optimize drainage, which also creates an opportunity to switch to creeping bentgrass varieties that are more disease tolerant and deliver better playing conditions. 

In situations where rebuilding putting greens is not an option, sand-channel drainage can be installed to improve internal drainage. This type of drainage is a suitable option provided the cultural management program has kept pace with managing surface organic matter and there are no concerns with the physical properties of the topdressing layer that has developed since original construction. When compared to rebuilding putting greens, sand-channel drainage can be installed for a fraction of the cost. 

Not only is optimizing growing environments necessary to promote healthy bentgrass, direct sunlight and proper drainage are critical for creating a competitive advantage that favors creeping bentgrass over Poa annua. Low-light environments with poor drainage will encourage Poa annua encroachment. After the proper growing environments have been established, the agronomic program must be tailored to maximize creeping bentgrass performance.

Nutrient and Disease Management

Creeping bentgrass does not have as high a nutrient requirement as Poa annua, especially regarding how much nitrogen is needed. Applying between 1 and 2 pounds of nitrogen per 1,000 square feet per year commonly yields high-performing creeping bentgrass putting greens. Of course, every golf course is different and this is only a general recommendation. Nitrogen fertility should be applied to aid recovery from traffic and ball marks, as well as stress caused by maintenance and environmental conditions. However, applying excessive nitrogen negatively impacts performance by promoting excessive growth, which will encourage Poa annua encroachment and result in excess thatch accumulation.

Minimizing nitrogen inputs will help control thatch accumulation in creeping bentgrass greens. Of course, a cultural management program must also be in place where organic matter removal and dilution properly maintains the mat layer, but overfeeding the putting greens will only lead to turf health and playability issues. The Green Section Record article “New Trends in Aeration and Organic Matter Management” is a great resource for setting up your organic matter management program.

A soil nutrient analysis should be conducted once or twice yearly to guide applications of all other nutrients. Should the nutrient analysis reveal a high pH, or if it is known that the pH of the soil profile is high, proactive measures should be taken to prevent take-all patch disease outbreaks. This disease is more prevalent when the soil pH is higher and can severely impact creeping bentgrass performance. From a fertility standpoint, acidifying fertilizers like ammonium sulfate or manganese sulfate can be used to buffer the pH and reduce the likelihood of disease outbreaks.

Because the take-all patch pathogen infects putting green roots during the shoulder seasons, curative applications for disease control are not effective. Once turf health issues are realized in the summer months, the damage has already been done. Accordingly, a preventative disease control program should be in place for take-all patch and other common turfgrass diseases, such as dollar spot. Another disease to scout for is bentgrass dead spot, especially if new creeping bentgrass greens are being managed. This disease is often confused with dollar spot, microdochium patch, cutworm damage, ball marks or copper spot, so sending samples to a plant pathologist will be necessary if one of these issues is thought to be causing turf decline but recovery is not occurring. Resources like NC State TurfFiles and the article “Chemical Control of Turfgrass Diseases” are excellent for developing an effective disease control program.

Plant Growth Regulators and Poa annua Suppression

Fertility is only half the story when it comes to managing growth on creeping bentgrass putting greens. Plant growth regulators (PGRs) are a key component of many agronomic programs to help maintain consistent playing conditions while simultaneously suppressing Poa annua. USGA agronomists observe trinexapac-ethyl, paclobutrazol, flurprimidol and prohexadione-calcium all used at golf courses with creeping bentgrass putting greens. Paclobutrazol and flurprimidol will suppress Poa annua and regulate creeping bentgrass growth, while trinexapac-ethyl and prohexadione-calcium offer growth regulation but are less aggressive on Poa annua.

Some superintendents find using one of these PGRs delivers the results they are looking for, while others have tweaked their agronomic programs to apply these products in combination. Superintendents may also use certain PGRs at different times of year to deliver specific results. For example, paclobutrazol or flurprimidol may be used during the shoulder seasons to suppress Poa annua and regulate growth but a switch is made to trinexapac-ethyl or prohexadione-calcium in the summer for growth regulation. Stressful weather conditions are often enough to suppress Poa annua without the use of PGRs like paclobutrazol and flurprimidol, and these conditions create a competitive advantage that favors creeping bentgrass.

With that being said, high-quality playing conditions can be produced on creeping bentgrass putting greens without the use of PGRs, or with PGRs removed from the management program during stressful times of the year. The Green Section Record article “Managing Bentgrass Putting Greens Without Plant Growth Regulators” can be referenced to help determine how and where PGRs fit in your bentgrass management program, if at all.

Careful water management during the most stressful stretches of the summer is a way to take advantage of creeping bentgrass’ drought tolerance to suppress Poa annua. By preparing putting greens to their ideal moisture range every morning, the turf should have enough water to make it through the day. Of course, greens should be monitored for drought stress and syringed if needed, but Poa annua will be suppressed by avoiding unnecessary syringing through the most stressful part of the day. Responsibly managing water will also help to deliver firm conditions that golfers desire.

Surface Management

Creeping bentgrass naturally wants to grow laterally, so practices to encourage more upright growth are necessary to deliver the best possible putting conditions. Instituting these practices translates to improved ball roll. Superintendents have access to a variety of equipment to manage lateral growth and promote smoother and truer conditions, but these techniques should be used carefully to avoid damage.

Balancing frequency and aggressiveness are critical when it comes to implementing practices like brushing, grooming and vertical mowing on bentgrass greens. Bentgrass is vulnerable to traffic damage, so a practice that can be beneficial in small doses can easily become detrimental if done too often, too aggressively or at the wrong time. Every course is different, so adding these practices to the program or adjusting their frequency should be done in small increments. The Green Section Record article “Grooming, Verticutting and Vertigrooming: Similarities, Differences and Keys to Success” does an excellent job of explaining how these practices can be implemented to maximize putting green performance. In general, less-aggressive and more-frequent brushing and grooming is less disruptive and will provide more-consistent conditions on bentgrass greens.

Consideration must also be given to the amount of traffic that is being placed on creeping bentgrass as turf decline can occur when this grass is managed too aggressively. Maintenance practices like mowing and rolling play an important role in delivering quality putting conditions, but as these practices are performed more frequently to meet ever-increasing expectations, more stress is placed on the turf. Remember, creeping bentgrass is not as traffic tolerant as Poa annua. Excessive wear can create thinning, which results in poor playing conditions and an opportunity for Poa annua encroachment. 

Given the high volume of traffic that is experienced near the edges of greens, preventative measures are often put in place to reduce wear. These practices can include the use of turning boards on collars, or a different mower setup for the cleanup pass. Using a solid or segmented front roller and raising the mowing height 0.005 inches on the cleanup mower are strategies that are often implemented to protect bentgrass putting green perimeters. 

At some facilities with creeping bentgrass putting greens, the decision has been made to eliminate collars entirely due to the challenges associated with maintaining a healthy stand of turf around the putting greens. When this decision is made, an intermediate rough is typically installed to create a transition between the putting green and the rough. If the golfers at your course are not willing to go collarless, reducing the height of creeping bentgrass collars can actually improve turf health. A height between 0.200 and 0.250 inches will often yield high-quality creeping bentgrass collars. 

Data Collection

Data collection is a great way to evaluate the impact of the different practices employed to maximize bentgrass putting green performance. It can highlight where adjustments need to be made and help the superintendent demonstrate how practices improve putting green performance. Tracking putting green metrics like clipping volume, speed, firmness and smoothness, and benchmarking them against surface management practices like mowing, rolling, brushing, grooming, vertical mowing, topdressing and PGR applications is becoming more popular throughout the golf course industry.

Green Section Record articles such as “A Quick-Start Guide to Putting Green Data Collection” and “Addressing Common Concerns About Data Collection” detail how to use data collection to your advantage. Do not expect an epiphany to take place in the first few weeks of putting green data collection. It takes time to build a database that allows you to accurately identify trends and determine where adjustments to the agronomic program can be made to better balance turf health and playing conditions. Data collection is not only beneficial for aiding decision-making, it also makes it possible to communicate more effectively, especially when it comes to technical matters that golfers may not intuitively grasp. 

Summary

Creeping bentgrass putting greens can without a doubt deliver conditions that meet and exceed golfer expectations provided agronomic programs are tailored to protect the turf against its weaknesses and maximize its strengths. The importance of proper growing environments cannot be overstated. Being mindful of traffic from golfers and maintenance practices is also critically important to successful bentgrass management. Anything that causes bentgrass to thin out will create poor playing conditions in the short term and encourage Poa annua invasion over time. If you want to keep the greens primarily bentgrass, maintaining a dense stand of turf is essential – even if that means backing off on certain practices during stressful conditions.

It is no coincidence that superintendents who deliver consistently high-quality bentgrass greens are routinely evaluating their programs to see whether changes need to be made. Data collection is a valuable tool that can help unravel how agronomic practices are impacting putting conditions, but the lessons learned from past experiences should be a factor as well. Developing a balanced agronomic program that steadily yields high-quality putting greens, regardless of turf species, is both an art and a science.

References

Russell, T.R., Karcher, D.E., & Richardson, M.D. (2019). Daily light integral requirement of a creeping bentgrass putting green as affected by shade, trinexapac-ethyl, and a plant colorant. Crop Science, 59, 1768-1778. doi.org/10.2135/cropsci2018.08.0501

Yasin, M., Rosenqvist, E., & Andreasen, C. (2017). The effect of reduced light intensity on grass weeds. Weed Science, 65(5), 603-613. doi:10.1017/wsc.2017.17