THE HEAT IS ONThe first decade of the 21st century has seen ultradwarfbermudagrassvarieties replacing bentgrass on putting greens in the Southeast.BY CHRIS HARTWIGER

The motto of the Olympic games is"Faster, Higher, Stronger" (Citius,Altius, Fortius), but it could also apply

to the selection of grasses on putting greens inthe Southeast Region. Dating back to the earlydays of golf, the unique climate of the southernportion of the transition zone has never been anideal fit for either bentgrass or bermudagrass forputting greens, nor has it excluded either species.The result has been an evolution of regrassingputting greens with improved grasses. Thelineage roughly follows this pattern dating backto the early 1950s: common bermudagrass,Tifgreen, Tifdwarf, Penncross, more heat-toler-ant bentgrasses, and ultradwarf bermudagrasses.Breeders develop the varieties, universityresearchers and superintendents perfect themanagement, and ultimately golfers determinewhich varieties come or go. And the processcontinues today.

The period since the early 2000s has seenthe emergence of the ultradwarf bermudagrassvarieties in the region. While the earliestadopters of the ultradwarfs were convertinggreens from Tifdwarf or Tifgreen, the periodsince 2005 has seen an acceleration in thenumber of courses removing their bentgrassputting greens and replacing them with ultra-dwarfbermudagrasses. Why is this occurring?There are several catalysts that led courses toconsider and select ultradwarf bermudagrassesfor their putting greens.• Improved wear tolerance eliminates the needto overseed.• Ability to peak the entire golf course atthe same time. This is desirable for hostingimportant golf events in hot weather months.• Management focus is shifted from multiplemonths of life support with bentgrass to a focuson playability.• Fewer inputs (fans, fungicides, etc.) and fewerdollars spent compared to bentgrass for mostcourses.

The first courses to make the switch wereones that chronically struggled to keep bentgrass

alive. They wen~ not seeking perfection, simplywanting live grass by the end of the summer.The second wave is happening now, and they arethe upper-end courses that desire to producehigh-level golf conditions in the summer months.They want to provide the combination of highergreen speeds and firmness that bentgrass greenscannot provide in the summer. The third groupare courses looking to find a grass that meetsgolfer expectations on as Iowa budget as possible,and the ultradwarfs are filling this niche.

As the momentum of regrassing increases,superintendents face the challenge of learningthe management of ultradwarf bermudagrass.Green committees and course officials familiaronly with bentgrass need to be aware of theskills, tools, and maintenance calendar necessaryto make ultradwarf successful. Fortunately, theearly adopters and university researchers havehelped hone the skills and practices necessary forsuccess. We have learned that the method ofmanagement is just as important, if not more so,as the budget alone.

In addition to mowing,regular use of verticalblades to groom orlightly vertical mow isbeneficial to surfacequality over the longterm. If vertical mowingis done too deeply, thehealing time will beextended.

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This article is dedicated to courses consideringa change from bentgrass to ultradwarf in thetransition zone. It is structured in two parts. Thefirst part highlights the most common problemsto avoid and solutions to assist, if these problemsoccur. The second part describes key practicesthat must be well executed to have a successfulultradwarf bermudagrass putting green.

This soil profile is nowmore than eight yearsold. The green wasconstructed usingstraight sand, andmanagement wasdifficult until someorganic matter hadaccumulated in theupper rootzone.

PITFALLS TO AVOIDOverseedingProblem: For decades, overseeding was a stapleon Tifgreen and Tifdwarf bermudagrass puttinggreens, the goal simply being to provide a goodputting surface in the winter and spring months.In most of the region, Tifgreen and Tifdwarfdid not have the wear tolerance to provide anacceptable putting surface on courses with heavywinter and spring play. The downside of over-seeding was and still is the significant disruptionto the golf experience in the fall and during thetransition in the spring. These courses become

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caught up in a late spring/early summer cycleof 1) fertilize heavily through June, July, andAugust to fill in bare areas after the overseedingdied; 2) aerate heavily in midsummer to mitigateall the organic matter deposited by the overseed-ing and bermudagrass base; 3) fertilize heavily torecover from aeration; and 4) mechanically prepthe greens for overseeding again in early fall.No wonder so many clubs jumped to bentgrasswhen pioneering superintendents proved theycould keep bentgrass alive during the summermonths!

Solution: There are several reasons not tooverseed an ultradwarf The first one is itsimproved wear tolerance due to the morestoloniferous growth habit of ultradwarf grasses.Champion bermudagrass is a good example.Champion has 93 percent greater shoot densitythan Tifdwarf, and the number of stolons forChampion is 2.6 times greater than Tifdwarf and2.8 times greater than Tifgreen (Beard andSifers, 1996). A wear study showed Champion tobe far more wear tolerant than Tifdwarf, with 32percent more surviving green leaves and shootsthan Tifdwarf after 1900 revolutions on a wearsimulator (Beard and Sifers, 1996). In the field,all the ultradwarf bermudagrasses hold up wellunder winter play, assuming there are notcompounding stresses such as shade.

A second reason not to overseed is nitrogenmanagement. For overseeding to be successful, itis fertilized at a time of the year not beneficialfor the bermudagrass base. All the nitrogen isnot released during the overseeding period, andresidual nitrogen released the next summer islikely to give the superintendent problems withunwanted growth.

A final reason to avoid overseeding is theelimination of shade, and details are included inthe next section.

ShadeProblem: Whether sunlight is blocked by clouds,trees, or taller turf, reducing light quality andlength will take its toll on ultradwarf bermuda-grass. Too much shade will make it difficult, ifnot impossible, to produce desired conditions.The symptoms of excess shade are not hard tospot: thin turf that is not able to withstand andrecover from stressful events, including golferand equipment traffic, turf diseases, and routinecultural practices such as mowing, grooming,and core aeration.

Solution: Assessing how much shade is toomuch is difficult for golf course superintendentswho are making the switch from bentgrass toultradwarf bermudagrass. Although results fromDr. Grady Miller indicate that "TifEagle andChampion bermudagrass are capable of sustain-ing quality better than other dwarf grasses,"superintendents converting from bentgrass tobermudagrass need to remember that bentgrasshas better shade tolerance than ultradwarf ber-mudagrass (Miller and Edenfield, 2002). If shadeis a problem on a bentgrass putting green, it is agiven that the problem will be magnified withan ultradwarf putting green. However, there aresure to be other marginal areas where shade islikely to influence an ultradwarf putting green.What is a golf course to do? The followingobservations from the field and research resultscan help.• Increase the quantity and quality of light aputting green receives through selective removalof trees. Dr. Bert McCarty and Todd Bunnellfound that a minimum of eight hours of sunlightis required to provide acceptable turf quality inTifEagle bermudagrass in a Clemson researchproject (Bunnell and McCarty, August 2004).They also found that 12 hours of sunlight wasoptimal for an ultradwarf bermudagrass(Bunnell and McCarty, October 2004).• There are situations where no more trees canbe removed and sunlight is still limited. Bunnelland McCarty found that applications of theplant growth regulator Primo and an increasein mowing height improved the quality of

TifEagle bermudagrass (Bunnell and McCarty,October 2004).

Extremes in Nitrogen FertilizationProblem: Memphis Country Club has areputation for some of the finest ultradwarfbermudagrass putting greens in the region.When discussing management strategies,Memphis Country Club superintendent RodneyLingle commented that ultradwarf bermuda-grasses are much more efficient users of nitrogenthan their predecessors, Tifgreen and TifdwarfIn other words, a little nitrogen goes a longway. This is confirmed in the field by far morefrequent observations of mower scalping thanlean, off-color putting greens.

Too much nitrogen is easy to identify becausemower scalping will occur, and it can occurquickly. Many times an employee will reportback to the maintenance facility that somethingmust be wrong with the mower because it isscalping severely. Usually the mower is fine, butthe growth of the grass has accelerated to thepoint of scalping. Mild cases of scalping can bedetected on the downhill side of the mower passwhen mowing on a slope.

Too little nitrogen is more difficult to identify.Typically, color will be poor, although if iron,magnesium, or manganese have been appliedrecently, color may not be the best indicator .Density may become more open, and there willbe slower recovery from mechanical stress.

Solution: How much nitrogen to use each yeardepends on multiple factors, including rootzone

Regulartopdressingwill smooththe surfaceand aid indilution oforganicmatter.

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Plenty of leaf tissue,but few stems willbe brought up whengrooming or verticalmowing is done at theproper depth.

nutrient holding capacity, the length of thegrowing season, seasonal rainfall, and desiredlevel of playability. Refer to the section onnitrogen management for details.

Poor Quality WaterProblem: Poor quality water is a major hurdle toanyone hoping to successfully manage ultradwarfbermudagrass. Elevated levels of sodium, solublesalts, and/or bicarbonates all can cause seriousturf quality issues. Books have been writtenabout the impact of water quality on turf, and ifyour golf course has poor water quality, carefulstudy and analysis are needed before selecting anultradwarf

Solution: The most effective option to over-come poor water quality is to find a better watersource for the putting greens, but this may not bepossible in most cases. Because of the complexityof this topic and the constraints of space, a list ofreferences for further study is noted below. Inextreme cases, ultradwarfbermudagrass may notbe sustainable and it may be advisable to considerseashore paspalum.Carrow, R. N., M. Huck, and R. R. Duncan. 2000.Effective use of seawater irrigation on turfgrass. USGAGreen Section Record. January/February. 38 (1):11-17.Carrow, R. N., M. Huck, and R. R. Duncan. 2000.Effluent water: Nightmare or dream come true. USGAGreen Section Record. March/April. 38(2):15-29.Carrow, R. N., M. Huck, and R. R. Duncan. 2000.Understanding water quality and guidelines for manage-ment: An overview of challenges for water usage on golfcourses for the 21st century. USGA Green Section Record.September/October. 38(5):14-24.Carrow, R. N., M. Huck, and R. R. Duncan. 2000.Leaching for salinity management on turfgrass sites. USGAGreen Section Record. November/December. 38(6):15-24.

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Carrow, R. N., and R. R. Duncan. 1998. Salt-affectedturf grass sites: Assessment and management. Ann ArborPress, Chelsea, Mich.

Construction Issues: Straight SandRootzone and Variable Mix DepthProblem: In this section there are two rootzoneissues to deal with. Variable mix depth describesa condition in a single putting green where thedepth of the rootzone mix varies significantlythroughout the putting green cavity. Thedepth of the rootzone mix has a big impact onthe amount of water that will be held at fieldcapacity. The USGA Guidelines for PuttingGreen Construction recommend a rootzone of12 inches. Deeper rootzone mixes have a highergravitational head and will hold less water, thusbeing prone to droughtiness. Shallower rootzonemixes will hold more water and be prone toexcess wetness. Both shallow and deep mix canexist in a single putting green, making watermanagement difficult.

A second rootzone issue for ultradwarfsis a straight sand rootzone mix. Straight sandstypically have low nutrient holding capacity(CEC) and low water holding capacity. Researchat Clemson University on ultradwarf establish-ment in greensmixes with differing water holdingcapacity found that the length of establishmentincreased on a mix with a blend of95:5 sandipeat mix compared to mixes with 85:15 sandipeat. This is confirmed in the field, as superin-tendents experience difficulty managing waterand nutrients in straight sand or near straightsand rootzone mixes.

Solution: Variable mix depth must be dealtwith through irrigation freqency and quantity.Absent rainfall, the two greatest influences onsoil moisture are the uniformity of coverage bythe irrigation system and the depth of the root-zone mix. It may be beneficial to conduct anaudit of irrigation coverage and a study of root-zone depth for each putting green. Althoughtime consuming, it is important to know theareas of the green that receive more or less waterthan desired and how they match up withshallower or deeper areas of rootzone mix. Setup irrigation cycles based upon the wettest areason each green. It will be necessary to add supple-mental hand watering to provide an appropriateamount of water for the ultradwarf plants.

The difficulty in managing a straight sandrootzone will become less over time, as more

organic matter is deposited from plant growth.Some have achieved success by adding amend-ments to increase nutrient holding capacity.

Mechanical InjuryProblem: One of the go-to maintenance practicesof Tifgreen and Tifdwarf bermudagrass varietieswas an aggressive dethatching once or twice aseason. The putting greens would appeardestroyed, but with a shot of fertilizer, water,and warm weather, the putting greens cameback thicker and denser than before. Ultradwarfbermudagrass varieties do not like this type oftreatment at all, and they will rebel in the formof extended recovery and bumpysurfaces for several months.Research by Dr. Wayne Hannaof the University of Georgiashowed that despite differingrates of nitrogen or plant growthregulator, aggressive dethatchingrequired a minimum of at leastsix weeks of recovery. This istoo much recovery time, giventhe requirements of play.

Solution: Aggressive dethatch-ing is not advised. Refer to thesection on surface managementfor alternatives.

KEY PRACTICESWith a few hurdles out of theway, the final section discussesseveral key practices that are thebasis for excellent ultradwarfbermudagrass putting greens.Superintendents who can refinethese practices over time, inresponse to results on their golfcourses, will be rewarded.

Frequent watering does not have to meanoverwatering. Set up the irrigation cycles relativeto the wettest portion of each green. Hand waterslopes and chronically dry areas. Use wettingagents, too. Research at Clemson University andin the field has shown that wetting agent usedoes improve ultradwarf turf quality on sand-based rootzones (Martin and Camberato, 2002).

Mowing PracticesThe quality and attention to detail of a mowingprogram has a profound impact on the qualityand playability of an ultradwarf bermudagrassputting green. Once thought to be the domain

Frequent WateringThis may be a shock to many and heresy toothers, but it doesn't take long to dry down inthe top inch. Ultradwarf bermudagrasses areshallow-rooted, and most observed in the South-east have root systems of two inches or less, witha predominance of roots in the upper inch. Also,the density of many ultradwarf stands is incrediblytight, and it is common to see water running offslopes and not into the soil. The best results inthe field result from superintendents wateringtheir ultradwarfputting greens every day or twoduring the growing season.

of walking mowers only, there are numerouscourses in the region that have achieved theirstandards with triplex mowers. Given the diffi-cult economy, this number is certain to increasein the years ahead.

Regardless of mower type, keep several con-siderations in mind. First, ultradwarf bermuda-grasses do perform well at low heights of cutwhen the weather is cooperative (temperaturesand adequate sunlight). Leaf texture and densityappear to improve as the height of cut movesdown. However, as height of cut moves down,

Hand watering remainsan integral part of anultradwarf managementprogram.

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the amount of work behind the scenes increasesdramatically. A few factors to consider as mow-ing height is decreased are included below.

• More skill, precision, and time are necessaryto set up the mowers, requiring the mechanic toallocate more of his time to mowing equipment.It may mean that the mechanic must delegateother tasks.

Rotary brushes on awalking mower are agood tool to promoteupright growth andminimize the impactof grain.

• Inconsistencies in a mower are magnifiedwhen it is used on a putting green.

• Sharpness becomes more important. Moretime will be spent on bedknife and reelsharpening and adjustment.

• At lower heights of cut, more sand will bepicked up, necessitating the use of backupmowers after topdressing or requiring more timeon reel and bedknife maintenance.

• Expenditures for parts will go up.

An excellent summary of the considerationsfor long-term success can be found in an articleby Tom Cowan called "Going Low with Ultra-dwarf Bermudagrass Putting Greens," whichappeared in the November/December 2001issue of the Green Section Record.

Surface ManagementAs noted earlier, aggressive vertical mowing ordethatching is not advised. When most super-

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intendents think of the practice of vertical mow-ing, a corrective practice is brought to mind.Instead of waiting for a situation to occur thatwould warrant a corrective practice - in ourcase an excess of undiluted mat at the surface -success can be achieved by a preventativeapproach through frequent grooming. Groomingin this article refers to the depth of the blades,not the equipment used. Frequent groominghelps reduce the influence of grain and results inadditional clipping removal by a follow-upmowing. The three-step regimen of 1) amorning mow, 2) light grooming with verticalmower blades on a triplex mower, and 3) asecond mowing, has worked well in the field.Small, shallow channels may be noticeable, butthey are not disruptive to play and not injuriousto the turf because the depth is so shallow. Thegrooming practice helps stand up the grassbetween the small channels, and the secondmowing is effective in removing even moreclippings without an adjustment in mowingheight. These channels also aid in future lighttopdressing incorporation. For a more completediscussion of this topic, refer to an article byJohn Foy of the USGA Green Section thatappeared in the January/February 2008 issueof the Green Section Record.

Organic Matter DilutionIt has been said that the solution to pollution isdilution. The same can be said for organicmatter management in the upper rootzone. Coreaeration, surface sand topdressing, and judiciousnitrogen applications are tools for managingthe buildup of organic matter in the rootzone.Long-term success with any putting green in theregion must include an appropriate core aerationand sand topdressing program.

A popular trend in the region, and one thatis sound agronomically, is to complete all coreaeration on one date inJuly or August, using atechnique known as closecenter aeration. Eitherthe putting green is aerated twice on two-inchcenters, or an aerator with variable spacing isused to create a comparable number of holes persquare foot. All disruptive aeration is performedon one date, which is far friendlier to the busi-ness of golf than multiple aeration dates. A moredetailed discussion of this topic can be found inthe article "Aeration and Topdressing for the 21stCentury" that appeared in the May/June 2004issue of the Green Section Record.

Use of Plant Growth Regulatorsand Wetting AgentsTrinexapac ethyl (Primo) continues to be themost popular plant growth regulator used onultradwarf bermudagrass putting greens and is astaple on most of the best ultradwarf puttinggreens observed in the region. Primo is used toreduce the vertical growth rate and, in doing so,clippings are reduced and a higher quality of cutis achieved. Further dwarfing of the grassesoccurs, with Primo producing an even tighter,denser surface. University research has docu-mented some of these benefits, too (Bunnell andMcCarty, 2004).

Wetting agent use is more sporadic through-out the region. The results of two studies areworth noting with respect to wetting agent use.Drs. Camberato and Martin at Clemson foundthat wetting agent use is appropriate for optimumturf grass quality and localized dry spot avoidance.Dr. Keith Karnok (University of Georgia) offeredtwo comments in a recent article that should getthe attention of everyone who manages a sand-based rootzone. The first comment is, "Ourresearch has shown that most sand-based root-zones 18 months or older will have some degreeof soil water repellency." Also, "Research hasshown that if water-repellent soil is found inone portion of a turf grass area - in this case agreen - almost without exception, soil waterrepellency will be present throughout the greeneven though localized dry spots may not beapparent." These are compelling arguments forthe use of wetting agents.

Nitrogen ManagementManaging the rate of growth appropriately has amajor impact on playability. The most practicaland successful approach observed in the field isto make an early season, slow-release nitrogenapplication to provide a small and predictablebackground level of growth. As the temperatureswarm up, begin to spoon feed small amounts ofnitrogen every 7 to 14 days to bring the growthrate of the grass in line with expectations. Startwith smaller quantities, and if some scalpingappears, back off If vigor or growth response isnot fast enough, gradually increase the spoonfeeding amounts.

CONCLUSIONManaging ultradwarf bermudagrass in thetransition zone requires a solid understanding of

turf grass management fundamentals, but it alsorequires the artistry of a craftsman. For super-intendents who are switching from bentgrassputting greens to ultradwarf, less time will bespent on turf survival techniques and more timewill be available for creating the best playingsurface possible. Several stumbling blocks werepresented in the first part of the article, andavoiding them is a great first step. The remainderof the article presented several key areas that willform the basis of the management program.Think of these areas as a path to success and adestination that will not be reached. Each season,it is likely that small modifications will be madebased upon previous results. With diligence andan awareness of solid fundamentals, the newhorizon will lead to a bright day forsuperintendents and golfers.

Winter wear toleranceof ultradwarf bermuda-grasses is strong enoughthat overseeding can beavoided. The puttinggreen in the foregroundhas been painted to addcolor. The green in thebackground is in theprocess of beingpainted.

As an agronomist in the Southeast Region,CHRIS HARTWIGER has the luxury if being able tohone his golf game on both bentgrass and ultradwarfbermudagrassputting greens.

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