Pocket change

Managing creeping bentgrass greens surrounded by trees takes a special agronomic plan.

By Logan Freeman
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If I asked you or your closest colleagues what is the most difficult environment for growing creeping bentgrass, what would you say? Is it conditions of low humidity and high winds? Is it extreme cold or extreme heat? How about drought or too much rain?

Eight of the 21 greens at Mountain Branch GC in Joppa, Md., sit back within shaded tree-filled areas and need special management to look and play their best. Photos by Logan Freeman

All of these answers would be valid, as each presents its own list of challenges. In my experience, however, we superintendents tend to say that whatever we are currently dealing with at our own property is the most difficult. This is exactly how I am feeling right now.

When I first became the superintendent of Mountain Branch Golf Course in the fall of 2010, I quickly realized that managing pocketed creeping bentgrass greens would require every skill and technique that I had learned over 13 years of managing cool-season turf. Mountain Branch GC is an 18-hole, semi-private course in Joppa, Md., located about 20 minutes north of Baltimore and just west of the Chesapeake Bay.

The most detrimental environmental factors to the health of a creeping bentgrass green are shade (especially morning shade) and airflow.

The course is just over 10 years old, and the layout of Mountain Branch was a definite success, showcasing 18 great golf holes. During the construction of the course, several holes required the removal of trees, as the layout passed through dense deciduous forest. It is in these forested areas that the beauty of the course reaches its full potential and that the challenge to the golfer is at its highest point. However, it is in this same area where the management of cool-season turfgrass is most difficult as the conditions are less than ideal. Eight of Mountain Branch’s 21 greens sit back within shaded tree-filled areas. Six of these eight greens are what many of us in the turfgrass management industry would call severely pocketed: surrounded by tall dense stands of trees and thick underbrush on three sides.

As turfgrass managers, we all understand the importance of identifying the various microclimates that are present on our properties. Each green, tee and fairway presents its own unique set of conditions and management needs. The management needs of creeping bentgrass greens in pocketed microclimates may be the most intense and the most challenging of any other microclimate, especially when coupled with difficult to near impossible weather conditions. However, I believe you can greatly improve your chances of producing high-quality putting surfaces in this difficult environment, no matter which climate you operate in, with the right agronomic plan.

Observing conditions

How do I know that the greens on my property are pocketed? I take a good, long look at each one. That seems simple enough, right? However, sometimes it isn’t as simple as looking to see if there are trees surrounding a green. The effects of pocketing can be created by other objects or situations that lead to the same weakening of the turf. For example, buildings frequently affect a practice putting green. A clubhouse, banquet or wedding facility, fencing, landscaping, vehicles or a scoreboard could also create shade and restrict airflow. It is often a combination of several of these items that lead to the development of an issue. Rocky outcroppings or other geographical features can result in a pocketed green. The design of the green complex itself can lead to issues, especially if the green surround has high mounding or steep slopes.

Once you determine if your problem greens have the visual aspects of a pocketed microclimate, then look a little deeper: How does the green move through the seasons? In other words, does one green react differently or have issues that affect it but not others on your property? A perfect example of this is if snowfall tends to stay around longer on the green that you are having trouble with. Consider whether or not frost stays longer on your problem green(s) than on other greens. Does the soil temperature cool down faster in the fall, or is it slower to warm in the spring? This is often a good identifier of problem trees and the potential for shade and airflow issues come summer. In the case of pocketed creeping bentgrass greens, the true stressors will begin to become evident in summer.

Major stressors for pocketed bentgrass greens like deep shade and poor air flow become especially problematic in the summer months.

The most detrimental environmental factors to the health of a creeping bentgrass green are shade (especially morning shade) and airflow.

As a result of the decrease in light intensity and quantity, morphological changes begin to take place within the turfgrass plant. These can be identified if you look closely at the creeping bentgrass plants on your problem green(s). A shaded creeping bentgrass plant produces thinner leaves, fewer carbs (which prevent optimal growth) and taller plants (as a result of the elongation of the leaf. These plants also decrease in number and/or have delayed maturity, and they have decreased density because of fewer tillers, rhizomes or stolons. If your turf is showing signs of decreased density, you may also begin to see signs of pressure from weeds like goosegrass, crabgrass or Poa annua.

All of these signs are visible with close observation. However, issues involving airflow are sometimes less obvious but can be just as detrimental to the health of creeping bentgrass greens.

Restricted airflow caused by obstructions like trees, buildings and geographical features can lead to stagnant air. This stagnant air increases relative humidity and moderates temperature. Why are these environmental factors detrimental to the health of creeping bentgrass greens? If a green is pocketed and therefore has reduced airflow, the turfgrass plant’s many processes become restricted. For example, when airflow over the leaf tissue is minimized, a warmer and more humid environment develops around the turfgrass plant, thus increasing the threat of disease and reducing the efficiency of the plant’s ability to perform transpiration.

Another component of restricted airflow is temperature moderation. In a pocketed microclimate, temperature moderation can lead to the rapid decline of a creeping bentgrass green. A pocketed green located where the temperature is moderated might not get as hot as other greens on your property, but it also won’t cool down in the evening like the more open greens. The temperature will stay steady, which means during the summer (even at night) your pocketed creeping bentgrass greens are staying stagnant, hot, humid and under stress.

Management strategies

Restricted light and airflow on pocketed greens cause morphological changes to the bentgrass plant, resulting in a less dense stand of turf that can lead to increased weed pressure.

So do we just throw our hands up and say that there is no way that we can maintain creeping bentgrass in a pocketed microclimate? No, and here is why: With the implementation of a sound agronomic plan, you can greatly improve your chances of success. Here are some key best management practices that I have found that can help you turn your biggest problem — those troublesome greens — into your biggest success.

Fertility

Reducing nitrogen fertility on pocketed greens by 25 to 50 percent in comparison to nonpocketed greens can go a long way in preventing rapid growth that can weaken the creeping bentgrass in a pocketed environment, and it can help reduce the severity and risk of disease. Applying granular products that are a minimum of 25 to 50 percent slow release in the spring and fall can also aid in the reduction of rapid growth and can give an efficient and effective nutrient baseline.

In addition to granular products, using foliar products to bring the nitrogen and other nutrient levels up to your preferred target is extremely helpful. Remember that you are going to want to apply 25 to 50 percent less nitrogen than you would to your more open and healthy greens. I’ve found that a strong biostimulant package can be of great benefit during the high stress of the summer.

Mowing

Raise mowing heights before periods of high stress and walk-mow, if possible; however, this is not an option for every situation. One of the most important factors in managing pocketed microclimates may be training crew members how to rotate mowing direction and how to minimize stress to turf while turning the mowing equipment. When possible, alternate mowing and rolling to reduce stress.

Pest management

Developing a strong preventive program that involves rotating products with different FRAC codes based on tighter application windows can help eliminate disease outbreaks. The important thing to note is that the program should be preventive in nature, with an emphasis on eliminating unwanted stresses if possible.

Train crew members to scout for disease or anything that looks out of the ordinary, and develop a solid communication system among the crew and managers. Understand the different diseases that may be more likely to affect your pocketed greens.

Cultivation

The most important factor to remember is aerification. Maintaining good air exchange in the root zone will allow roots to flourish and the soil to dry out more effectively. As long as temperatures permit, routine light to very light topdressing can help keep the surface firm and smooth and can also help wick moisture from the soil in addition to giving support to a weakened plant.

Irrigation

Don’t overwater. Too much water is often more detrimental to turf health than not enough, but don’t limit water in an area that is already deprived of high-quality light. When it comes to pocketed creeping bentgrass greens, make sure the plant has enough water so that it can complete its necessary processes. Use wetting agents to maintain a balanced soil moisture level. Tools like soil moisture meters, although expensive, can prove very beneficial in the management of moisture levels.

Plant growth regulators

The effective use of cell elongation inhibitors like trinexapac-ethyl can help control excessive growth on pocketed creeping bentgrass greens.

Trial and error

In addition to these best management practices, there are other key areas that should not be overlooked. These include improving drainage; managing organic matter, wear and traffic; scouting for weed pressure in thinning turf; and developing a weed control program. All these in addition to the key BMPs help to provide sufficient light and airflow.

How do we go about achieving all of these best management practices listed above?

  • Locate and inspect drainage outfalls for proper operation. Use drainage cleanouts whenever possible.
  • Implement wear and traffic pattern rotation. If an area of a green is showing signs of thinning or stress, then every effort should be made to limit the amount of wear.
  • If shade and airflow issues are caused by manageable objects (for example, trees, underbrush), develop a plan for their removal or thinning. In cases involving shade, options are much more limited. If the shade is being caused by a tree then consider removing it. However, removing large numbers of trees is not always an option. In this case, focus on removing those that cause morning shade because cool-season turfgrass builds up its carb reserves in the morning. It is important to note that removing trees can result in other issues that can end up affecting airflow, which I have experienced first-hand. Removing several problem trees on one of my pocketed greens improved the light enough to cause overgrowth of the underbrush, resulting in a whole new management problem.
  • In situations where, for various reasons, the airflow-restricting objects can’t be removed, installing oscillating fans can go a long way toward improving the quality of the turf in a pocketed microclimate. If fans are not an option due to budget restraints, power availability or other issues, then using a turbine blower or a PTO blower can provide similar benefits.

Overall, managing creeping bentgrass in a pocketed microclimate is not an easy task and requires trial and error as no two properties are alike. It is up to the turfgrass manager to develop the best management practices that are the most effective and efficient for his or her individual property. Besides developing a sound agronomic program, the more important component of your success may be a strong support system of colleagues that can help you evaluate, plan and manage your program for the most difficult situation in which to grow creeping bentgrass.

Logan Freeman is the superintendent at Mountain Branch Golf Course in Joppa, Md., and a three-year member of GCSAA.