Here Comes Another Summer

By Chris Hartwiger and Patrick O’Brien, Agronomists
March 29, 2010

Fans are an excellent bentgrass survival tool during the summer months. The high technology of modern fans increases their effectiveness today. 

Many of our articles over the last year have focused on some aspect of ultradwarf putting greens. Bentgrass managers, we have not forgotten about you! Now is the time to begin putting your summer management plan into action. Below are a few topics that may help the summer go a little easier. We have included links to turfgrass research articles in case you wish to delve deeper into each topic.

Fan Use

Fans have become a staple on golf courses that have bentgrass putting greens. A decade ago, many courses with bentgrass putting greens had a handful of fans on the course. Today, it is not uncommon to find fans on all eighteen putting greens. Why? Fans have proven in research trials and in the field to be a valuable bentgrass life support tool.

Fan use is a question that tends to come up from time to time. Here are some common questions we receive:

What time of year should we begin using the fans? Research by Dr. Fred Yelverton shows that bentgrass root systems may begin to decline when soil temperatures increase above 75 degrees for a few hours each day. This appears to be a prudent time to begin fan use. Our experience suggests that fans run on a limited basis beginning in mid to late May, on average, with daily use beginning sometime in June.

How long should the fans run – during the day or for 24 hours? Data from Auburn suggests that running fans for 24 hours is more helpful to the bentgrass than running them only during the day. Of course, the turf manager must weigh the benefit versus the extra cost to run the fans for 24 hours. Practically speaking, we have found that many superintendents run their fans during the day in the early part of the summer, and switch to 24-hour use when conditions become extreme.

For more information, visit these links.


Venting is a term that applies to the practice of creating small, non disruptive holes in a putting green for the purpose of improving gas exchange, increasing water infiltration, and stimulating new root initiation. The term ‘venting’ is used instead of aeration because of the negative connotations golfers associate with the term ‘aeration.’ Venting is a golfer-friendly practice.

Dr. Bob Carrow of the University of Georgia found that ideal venting frequency in his research plots was every 21 days throughout the summer months. For more information, visit these links.

Raise Mowing Height

In an age of rising expectations for putting green performance, the recommendation to raise the mowing height on bentgrass putting greens to promote better summer survival is not popular with golfers. Of course, failed putting greens in late August are not popular to golfers, either. Nevertheless, science is on your side on this one.

The benefit of raising the mowing height in the summer can be explained by looking at the relationship between energy production (photosynthesis) and energy consumption (respiration) in the summer. As temperatures increase, the rate of photosynthesis in cool season grasses decreases, but the rate of respiration increases. Explained another way, energy production is slowing while energy consumption is increasing. This is not sustainable in the long term because, eventually, the turf is going to run out of fuel. Raising the mowing height increases the amount of leaf surface area, which increases the amount of potential photosynthesis. In essence, the higher mowing height is creating a bigger tank of fuel for the plant, and, hopefully, the fuel will not run out until cooler temperatures return in the fall. This concept is explained in much more detail in the article below:

Rolling Instead of Mowing

Mowing is a stressful practice to bentgrass putting greens in the summer months. Researchers at the University of Arkansas found that by mowing three times per week and rolling three times per week, green speeds remained consistent throughout the week. In the field, we have observed this practice used in the summer months, and superintendents report improved turf quality. Therefore, if stress is high, reducing mowing frequency and substituting rolling is an option to consider reducing stress.,Mowing%20Frequency,%20and%20Rolling%20Frequency%20Affect%20Putting%20Green%20Speed.pdf


We hope these tips and links are helpful to southern bentgrass managers this year. Summer is definitely the most difficult time of year for creeping bentgrass, and no one knows from year to year what challenges the weather will bring. Be assured that the USGA Green Section is ready and available to assist you in any way possible. We can be contacted at or

Source: Patrick O'Brien 770-229-8125 or  and Chris Hartwiger 205-444-5079 or 

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