Course Care: Non-Overseeded Ultradwarf Bermudagrass Greens

In the desert Southwest, eliminating overseeding on ultradwarf bermudagrass greens is rapidly becoming the new trend, partially due to poor bermudagrass recovery after overseeding, but mostly because golfers have discovered that non-overseeded greens offer better surfaces for more golf days. In the fall, when many overseeded greens are slow, wet and prone to pitch marks, ultradwarf greens are at their best. When the overseeded turf is weakening the following summer, and ball roll becomes inconsistent, non-overseeded greens often perform far better. However, there are more than a few misconceptions with respect to non-overseeded greens, both from an agronomic and playability perspective, which need be quelled before we move on and discuss specific management strategies.

As a few leading turf managers have already discovered, managing non-overseeded greens in the winter can be tricky, and there are a number of pitfalls that must be avoided. Several misconceptions and pitfalls are summarized in the following points:

·Misconception: Greens Firmness – In informal surveys, most golfers, golf professionals and even most turf managers perceive that non-overseeded greens are firmer, and therefore less receptive to golf shots than overseeded surfaces. This is simply not true. In fact, in every case where this author has quantified the firmness using the USGA TruFirm® on both overseeded and non-overseeded surfaces on the same green, the non-overseeded portion is always less firm. Most likely, the non-overseeded surface is softer, a result of more thatch mat, which leads us to the next bullet point.

Misconception: The practice of overseeding greens creates more thatch and organic matter than when not overseeded – true or false? Based on personal observations, it appears this statement is false. Although there is no research data to confirm this, in experience with measuring thatch and organic matter levels on both non-overseeded and overseeded greens, the non-overseeded surfaces always produce more thatch, at least in the desert Southwest. The bermudagrass grows for more days without competition from the cool season turf, and therefore produces a greater thatch mat.
Misconception: Traffic Damage – Course officials often express that their primary fear with non-overseeding is the damage from traffic, the potential for weak turf, and even bare ground. This is not the case. One golf property that regularly sees more than 60,000 rounds per year (80 percent between November and May) had no issues with traffic damage on non-overseeded ultradwarf surfaces.
Misconception: Ball Marks – Given that the non-overseeded greens are likely softer than their overseeded counterparts, one would assume that ball marks will be more prevalent. However, this has not been the case. In fact, all the turf managers that contributed to this article were in agreement that complaints about ball marks were non-existent or decreased substantially once overseeding was eliminated from the greens program.
Pitfall: Winter color – Right or wrong, the desert Southwest market demands green. This should not be a deterrent to eliminate overseeding from the program, it is merely an additional challenge the turf manager must address. Turf colorant technology has come a long way in recent years, and superintendents are now offering cosmetically attractive, non-overseeded greens in the dead of winter. Several turf managers offer their colorant strategies later in this article.
Pitfall: Green speed – One very real concern in the desert Southwest is excessively fast green speeds during extended periods of cold weather and negligible growth. However, with a sound fall setup program, green speed can be maintained at acceptable pace throughout the winter. Fall is the time to increase mowing heights and reduce mowing frequency. When growth stops in December or January, it is likely too late to increase heights.
Pitfall: Scarred hole plugs – Another concern when not overseeding greens is that old hole plugs recover slowly. If plugs are high and scalp, recovery will be slow, although colorants often hide such scars fairly well. Furthermore, if thatch is not aggressively maintained throughout the year, the turf around the outside edge of the hole plug often deteriorates in a half-moon pattern, forming a scar. This issue is seen throughout the year where horizontal stolons are allowed to grow unabated, but this is most problematic in the winter. Unfortunately, if hole scars are an issue at your course, substantial improvement will likely require several years of more aggressive surface grooming practices.

After reading the above-mentioned summary, your primary fears about not overseeding greens should have been addressed. Turf managers should take note of the pitfalls mentioned, including winter color, green speed and scarred hole plugs. With this in mind, the remainder of this article will focus on strategies that three turf managers have employed in the Southwest Region to overcome such pitfalls and endear golfers to non-overseeded ultradwarf greens.

Fall Management (The Setup Period)

Fall, which for the sake of this article includes October, November and a few weeks into December, is an important setup period for preparing for the onset of winter dormancy. The fall months are essential to encourage late season growth, increase heights, employ what are likely the last surface grooming practices for the year and begin using colorants.

How do you encourage late-season bermudagrass growth and color?

Charlie Costello, superintendent, Phoenix Country Club: We spray urea and/or calcium nitrate to supply about 0.10 lbs of N/1000 ft² every 7-10 days. Green spray dye is applied year-round, which warms the surface in the fall and encourages growth. Primo applications continue on a biweekly schedule, although rates drop from 14 ounces/acre/month during the growing season to as low as 3 ounces/acre/month in the winter.
Rob Collins, superintendent, Paradise Valley Country Club: Nitrogen inputs are increased from weekly applications at 0.10 lbs of N/1000 ft² to 0.25lbs/1000 ft², beginning in October and continuing through the end of November. Rates drop to 0.10 – 0.15 lbs N/1000 ft² during the winter. Green pigment applications begin sometime in mid-November when growth has slowed, but the turf remains green.
Bill Rupert, superintendent, Alta Mesa Country Club: Nitrogen is applied every two weeks at 0.10 lbs of N/1000 ft² during the summer. Once the humidity decreases and growth slows, nitrogen inputs are increased to 0.20 lbs/1000 ft² on a biweekly schedule. Green spray dye applications begin in early to mid-November.

How do you manage green speeds prior to winter dormancy?

Charlie Costello: Greens are double-cut daily with fixed-head mowers set at 0.110 inches through most of the fall. Target green speed ranges from 10-11 feet as measured by the Stimpmeter. In early November, mowing height is adjusted up to between 0.115 – 0.120 inches. Double-cutting is no longer employed when growth slows substantially, usually in mid-November.
Rob Collins: We discontinue double-mowing when growth slows in November. Mowing heights may increase by 0.010 to 0.020 inches, but green speeds must be maintained above 11 feet. It was interesting that last winter we had to lower mowing heights during the first week of January as green speeds slowed to about 10 ft. when temperatures increased for a few days.
Bill Rupert: We mow with floating head mowers and double cut and double groom daily at a height of 0.070 inches through the summer and into the fall. When overnight temperatures consistently stay in the mid 60s, heights progressively increase by about 0.005 inches per week, until we reach a maximum height of 0.130 to 0.140 inches in the winter.

Do you conduct any late-season surface grooming practices?

Charlie Costello: Fairly aggressive verticutting is employed once per month, using the “backtrack” method, but the last of these practices is completed in late August/early September. Grooming blades continue to run daily through October, set at or slightly below mowing height. The frequency reduces to four-five days/week through November. No grooming is conducted in December and January, but brushing continues four-five days per week. Sand topdressing with a medium-sized sand is applied twice monthly through November with walking rotary spreaders set wide open in two directions. Topdressing frequency drops to once per month in December and January and the rate is reduced considerably – only one pass is made and the spreader setting is reduced a few notches.
Rob Collins: Weekly verticutting with blades set at 0.020 inches below zero will continue until mid-October. We always test an area a day or two before and adjust in 0.005 inch increments. Topdressing with medium-sized sand is practiced weekly, and will likely continue into the winter, although the frequency may be reduced. We groom three-four days per week through early November. Brushing, both with gear-driven models and front-mounted brushes (used on alternate days), is practiced three-four days per week, but we will reduce the frequency based on clippings and weather.
Bill Rupert: Grooming continues through the fall at even or 0.005 inches below mowing height. Verticutting is practiced every three weeks through September at 0.010 inches below the height of cut and will resume in February.

Winter Management (The Dormancy Period)

December, January and portions of February coincide with minimal growth or complete dormancy for ultradwarf greens in the desert Southwest. Turf managers often continue to supply nitrogen in light amounts in the event that sporadic warm temperatures may encourage growth. The biggest concerns during the winter months are excessively fast greens, lack of recovery on old hole plugs, and winter color. Our contributing superintendents share their winter tactics in the following discussion.

How do you manage greens speeds during the coldest months of the year?

Charlie Costello: Mowing height is increased to 0.130 inches in December and that height is maintained through February. Greens are mowed six days per week and rolled the seventh day. Green speeds often range from 12 to 12 ½ feet as measured by the Stimpmeter. We can slow them down by brushing.
Rob Collins: Mowing frequency changes to only once per day, and we may skip one day per week. Heights may increase, but only by 10 to 20 thousandths. We track growing degree days (GDD, base 55) (/content/dam/usga/pdf/imported/heatunits.pdf) and weigh clippings daily. When the GDD units drop into single digits, growth slows and speed increases. We will see periods of double-digit GDD, in which several days later the clippings will increase and we may need to lower heights or roll to maintain our target speeds of about 12 ft.
Bill Rupert: We mow two-three times per week in the winter. The greens are cleaned of debris the remaining days for play, and sometimes rolled, depending on their pace. Our floating head mowers are set to 0.130 – 0.140 inches. The target green speed ranges from 10-11 ft.

How do you preserve the integrity of old hold plugs?

Charlie Costello: This is our biggest challenge and the primary source of complaints we may hear. The regular green dye applications seem to help, but we recognize that more aggressive and more frequent cultural practices must be employed during the growing months to see real improvement.
Rob Collins: More aggressive thatch and organic matter reduction practices over the last three years have really reduced this problem, although it may never entirely go away. We paint the soil above the hole liner daily and reduce the hole changing frequency to five days per week during December, January and a few weeks in February.
Bill Rupert: Scarred hole plugs is my No. 1 complaint. We have tried a number of tactics to reduce this problem, but nothing seems to work very well. Ultimately, we need to be more aggressive in managing horizontal growth throughout the year.

How do you maintain green color during the winter months?

Charlie Costello: Green dye is applied on a 7-10 day schedule. A walking boom sprayer is set to apply 1.5 oz of Green Toes^® dye/1000 ft² (about 6 quarts over 3 acres) and 0.20 lbs of N/1000 ft², using flat fan nozzles. The sprayer is pulled behind the applicator to avoid foot prints and wheel marks. Three minutes of water is applied, with overhead irrigation following each application.

Conclusion

Non-overseeded ultradwarf bermudagrass greens have the potential to provide smooth, consistent and fast putting surfaces for more golf days when compared to the same greens when overseeded. However, endearing golfers to non-overseeded surfaces has not been easy in the desert Southwest. Probably the biggest complaint from golfers is the scarred hole plugs and the color difference when compared to overseeded greens, but those comments fall to the eye of the beholder. The late Steve Jobs once said: “Most people make the mistake of thinking design is what it looks like, ‘Make it look good!’ That’s not what we think design is. It’s not just what it looks like and feels like. Design is how it works.” Much in the same way, putting green presentation is not all about how it looks; a great putting surface offers a combination of cosmetics and playability.

Brian Whitlark is an agronomist in the Southwest Region of the USGA Green Section. He visits courses in Arizona, California, Nevada and portions of Mexico.

Thank you to Charlie Costello, superintendent at Phoenix Country Club, Rob Collins, superintendent at Paradise Valley Country Club, and Bill Rupert, superintendent at Alta Mesa Country Club for their contributions to the article.

Non-overseeded ultradwarf greens can offer smoother and faster putting surfaces than their overseeded counterparts, but managing them in the winter can be tricky