Greening up the Greens


You are a student intern for the summer at Fall Oaks Golf Course in eastern Nebraska. After working there for a month you notice that the greens are not in the greatest condition. In the morning the greens are a lush green color, but then during the middle of the day areas turn bluish-green to brown. The greens seem to recover their green color later in the day, but the plant density (thickness of the greens) has been steadily decreasing since you started working there in early June. The other intern, who worked there last summer, comments that it sure didn’t look like this last year!

Greens under heat stress turn bluish-green to brown in color and plant health decreases.(Roch Gaussoin, 2005)

You decide to impress your boss by taking the initiative to determine how to correct the problem. Before you can make a recommendation, though, you need to gather some information to figure out what the problem is and how it can be remedied.

Your first step is to find out more about the management practices for the greens. You can ask your boss, a Certified Golf Course Superintendent, any of the following questions.

How much is the golf course used?

There is a significant level of rounds played (> 45,000 per year), with most summer rounds being played in the morning or late afternoon.

What are the greens like?

The greens are creeping bentgrass mowed at a 0.10 inch (yes, only a tenth of an inch!!)

Are the greens fertilized regularly?

The greens are fertilized with liquid fertilizers every 14 days.

How is pest control addressed?

The greens receive routine pesticide applications to suppress disease and insect activity.

Are the greens receiving enough water?

The greens are irrigated with a state of the art, computer controlled irrigation system using on-site weather information and University based estimates of evapotranspiration (ET) every night and the irrigation system is functioning correctly.

What was the temperature in June & July of 2004? See figure below
What was the temperature in June & July of 2005? See figure below



Based on the information you have so far, what do you think is the most likely cause of the problem?  

Looks Good! Correct: Based on information you gathered from your boss, the greens are receiving adequate fertilizer and water, and proper precautions against insects and disease are being taken. With the creeping bentgrass variety being selected specifically for its tolerance to low-mowing height and durability to traffic, foot-traffic from golfers is unlikely to be the cause of the problem. Also, note that the greens seem to perk up in the mornings and evenings, which happens to be when most rounds are being played. This would not seem to indicate that high-traffic could be the problem. All things seem to indicate that heat-stress is the cause. Note the temperatures for June and July 2005 are quite high. They are much higher than the June and July 2004 temperatures, which would explain why this was not a problem last year. It would also explain why the problem is alleviated in the mornings and evenings when the temperatures would be cooler.

What is happening to the environment around the grass plants as the air temperature increases (providing no other conditions change)?

To review this concept, visit Transpiration - Factors Affecting Rates of Transpiration.

Looks Good! Correct: As temperature increases, the water holding capacity of that air increases sharply. The amount of water does not change, just the ability of that air to hold water. Because warmer air can hold more water, its relative humidity than the same air sample at a lower temperature, or it is ?drier air?. Therefore, warmer air will increase the driving force for transpiration.

How do the grass plants cool themselves?

To review this, visit Transpiration - What and Why.

Looks Good! Correct: During transpiration, water evaporates or converts from a liquid to a gas at the leaf cell and atmosphere interface, energy is released. This exothermic process uses energy to break the strong hydrogen bonds between liquid water molecules; the energy used to do so is taken from the leaf and given to the water molecules that have converted to highly energetic gas molecules. These gas molecules and their associated energy are released into the atmosphere, cooling the plant.

In addition to cooling the temperature of a plant, transpiration is important to a plant for many reasons. Which of the following is NOT an important result of transpiration?

To review this concept, visit Transpiration - What and Why?

Looks Good! Correct: During transpiration, water entering the plant through roots in the soil carries nutrients vital to the plant?s growth. Water exits the plants through open stomata in the leaves. The open stomata allow not only water to exit, but also CO2 to enter for use in photosynthesis reactions. Water is also a crucial component for many other biochemical process in the plant, as well as creating turgor to keep the plant standing.

When the transpiration rate is extremely high, plants are highly susceptible to __________ .

To review this concept, visit Transpiration - Major Plant Highlights.

Looks Good! Correct: When transpiration rates are extremely high, the water molecules can be “pulled apart” breaking up the flow of water and causing air bubbles to form in the xylem resulting in cavitation.

The creeping bentgrass plants on the greens protect themselves from losing too much water by…

To review this concept, visit Transpiration - Major Plant Highlights.

Looks Good! Correct: The stomata are the primary control mechanisms that plants use to reduce water loss. Closing the stomata prevents water from exiting the plant and therefore stops transpiration and further water loss.

If the grass plants are not transpiring, what will happen to them?

To review this concept, visit Transpiration - What and Why.  

Looks Good! Correct: All of the above. During transpiration, water leaving the plant provides cooling for the plant. The open stomata necessary for transpiration to take place allow CO2 to enter for photosynthesis reactions. Transpiration encourages water uptake, which is important for biochemical processes requiring water and to support the plant.

Why do the greens seem to recover in the evenings and mornings?

To review this concept, visit Transpiration - Major Plant Highlights.  

Looks Good! Correct: In the evenings and mornings, air temperature decreases enough for stomata to open again and resume transpiration. Therefore, not only do the lower air temperatures cool the plant, but the resumption of transpiration also cools the plant, as well as allowing it to regain turgor pressure, and resume photosynthesis and other biochemical processes reliant upon water.

How could you get the greens to recover during the day?

To review this concept, visit Transpiration - Major Plant Highlights.  

Looks Good! Correct: Since heat stress is the cause of the problem, finding a way to reduce the air temperature cool the plants will be the only way to allow them to recover.

Describing your findings to your boss, he recommends a management technique called “syringing” be done to the greens in mid-afternoon. He describes “syringing” as a light application of water that is sufficient water to wet the green surface but move minimally down into the soil.



Why would this be effective when the roots are not receiving much moisture? To review this concept, visit Transpiration - Major Plant Highlights.

Looks Good! Correct: Explanation: There will be two effects, initially the water being cooler than the surface temperature, will lower the greens surface temperature. This effect will be relatively short. Then as the moisture evaporates from the leaf surface (essentially replacing a portion of the transpiration cooling effect that was inhibited by the environmental conditions) the greens surface temperature will be lower.

As a result of your accurate assessment and consultation with your boss, you begin syringing the greens. Over the next few days you see a marked improvement in their appearance.

Healthy greens on a golf course. (Roch Gaussoin, 2005)

Copyright 2005

Development of this lesson was supported in part by the Cooperative State Research, Education, & Extension Service, U.S. Dept of Agriculture under Agreement Number PX2003-06237 administered by Cornell University, Virginia Tech and the American Distance Education Consortium (ADEC) and in part by the New Mexico and Nebraska Agricultural Experiment Stations. Any opinions ,findings, conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.