selecting the right grass selecting the right grass with many warm-season turfgrass options...

Selecting TheRight GrassWith many warm-seasonturfgrass options available,determining the mostappropriate is a daunting task.

BY JOHN FOY

Ten years ago, if you were building orrenovating a golf course in the southernportion of the United States where

warm-season turfgrasses have traditionally beenused, grass selection was a simple proposition.Bermudagrass, and primarily the hybrid cultivarTifway (419), was the standard and was consideredto have very good overall adaptation for tee,fairway, and rough areas. Similarly, Tifdwarfbermuda was the standard for putting greens.However, golfer demands and expectations forfast putting speeds have also resulted in effortsto push bentgrass further south. In less than adecade, the turfgrass selection equation hasbecome much more complicated.

Introduction of the ultradwarf bermuda-grasses - Champion, Floradwarf, TifEagle, andMiniVerde - started the revolution and raisedthe bar for quality and conditioning of warm-season putting greens. The increase in the numberof entries in the National Turfgrass EvaluationProgram (NTEP) from a total of 26 (16 seeded,10 vegetative) in 1992 to 42 (29 seeded, 13vegetative) in 2002 clearly illustrates that a lot ofwork has been put forth to develop additionalbermudagrass options for fairways and roughs.Furthermore, while bermudagrass has long beenthe king of warm-season grasses, an increasingnumber of seashore paspalum and zoysiagrasscultivars or varieties are available today.

There has been a big slowdown in new courseconstruction in the United States; however, therehas also been a surge in course renovationprojects. In Florida alone, there were more than50 renovation projects slated for 2006, and it isestimated that a similar amount of work will beundertaken annually for the next several years.

RANGE OF ADAPTATIONTurgrasses have long been separated into twobasic groups based on their climatic adaptationand specifically the temperature range requiredfor optimum growth. The warm-season turf-grasses grow best in the temperature range of 80to 95 degrees F, whereas the cool-season turf-grasses exhibit optimum growth when tempera-tures are in the 60 to 75 degrees F range. Ingeneral, warm-season turfgrasses have betterdrought, heat, and wear tolerance compared tocool-season species, but they enter into a dormantstage and go off-color (brown) when temperaturesin the 50-degree F range or colder occur. Poortolerance to cold winter temperatures and winterkill are limiting factors in the distribution and use

Cool HumidCreeping bentgrassCreeping bluegrassFine-leaf fescues

Resurfacing of putting greens and conversionto an ultradwarf cultivar are the driving forcesbehind much of the project work being under-taken. Yet, there are also complete course renova-tion and replanting projects being performed, andthere are more than 100 courses being built acrossthe country annually. To assist in selecting the bestsuited and appropriate warm-season golf courseturfgrass options, the following is a review oftheir general characteristics along with guidelinesto use in the decision-making process.

SemicoolHumidCreeping bentgrassCreeping bluegrassPerennial ryegrassKentucky bluegrassFine-leaf fescues

Humid TransitionalPerennial ryegrassJapanese zoysiagrassKentucky bluegrassDactylon bermudagrass

of warm-season species through the upper tran-sition zone and northern portion of the UnitedStates. Geographic distribution of the warm-season turf grasses in relation to the major climaticzones of the U.S. is depicted in Figure 1.

There are approximately 14 warm-seasonspecies utilized for turfgrass purposes around theworld.2 However, for the remainder of this article,discussions will focus on bermudagrass (Cynodonspecies), seashore paspalum (Paspalum vaginatum),and zoysiagrass (Zoysia species) because they arecurrently the main species used on primaryplaying surfaces in North America. Buffalograss(Buchloe dactyloides) is a native species of the GreatPlains of North America and is extremely welladapted to semi-arid regions. Although improvedcultivars have been developed over the past fewyears, it is definitely under utilized.

Warm TropicalBermudagrass:

• hybrid• dactylon

Seashore paspalum

SPECIES/CULTIVAR ADAPTATIONFor selecting the best-suited warm-season speciesand cultivar, a number of factors need to be takeninto consideration. Across the country, irrigationwater availability and quality are major concernsfor golf courses. This brings to the forefrontwater usage rates, salinity tolerance, and droughtresistance as factors to consider. Also, it is essentialthat every effort be made to minimize potential

Warm SemiaridBermudagrass:


Seashore paspalumAmerican buffalograss

Semicool AridKentucky bluegrassAmerican buffalograssCreeping bentgrass

Semiarid TransitionalBermudagrass:


Japanese zoysiagrassAmerican buffalograss

Warm AridBermudagrass:


Seashore paspalum

Cool SemiaridPacificBermudagrass:


Seashore paspalumKikuyugrass

Cool HumidPacificCreeping bentgrassColonial bentgrassFine-leaf fescuesPerennial ryegrassCreeping bluegrass

Major turfgrass climaticzones and geographicdistribution of speciesin the United States(adapted from Beard2002).

2 GREEN SECTION RECORD

negative environmental impacts and conserveresources. Thus, pest problems and managementinputs such as fertilizer requirements need to becomponents in the selection equation.

WATER USAGE, SALINITY TOLERANCE,AND DROUGHT RESISTANCEAs a group, warm-season grasses have lowerwater use rates (based on mean summertimeevapotranspiration rates) compared to cool-seasonspecies. Buffalograss is at the head of the pack andhas a relative ranking of very low water usage. Itis followed by bermudagrass and then zoysiagrass,with low to medium rankings. Based on previousresearch, seashore paspalum is also ranked ashaving a medium water usage rate relative tothese other species.

New bermudagrass, zoysia, and paspalumcultivars have become available since these wateruse rate studies were conducted, and variabilityamong cultivars does occur. This is especially truewith seashore paspalum. There have been adver-tising and marketing claims that seashore paspalumneeds only 50% of the irrigation of bermuda-grass, but research conducted by Dr. Bob Carrowat the University of Georgia determined thatwater requirements of Sealsle I, which was themost drought-tolerant paspalum, are similar toTifWay bermuda.3 With proper nitrogen fertiliza-tion and irrigation management to maintainmaximum root system development, an additionalreduction in water usage of Sealsle I is possible. Inanother study conducted at Clemson University,it was found that improvements in water use ratesand drought tolerance have been achieved withsome of the newer bermudagrasses that are nowavailable. 1 Additional unbiased cultivar and speciesevaluation of this very important performancecharacter is needed.

In the past, salinity and water quality problemswere, for the most part, only an issue in arid tosemi-arid regions. Degradation of ground andsurface water supplies along with increased use ofeffiuent and non-potable water sources, however,has resulted in salinity tolerance becoming a con-cern in humid regions as well. Bermudagrass, andin particular the hybrid cultivars, are ranked ashaving very good salinity tolerance along withzoysiagrass. Seashore paspalum is considered themost salt tolerant of all warm-season species, andseveral cultivars are available today that also haveimproved turf grass quality characteristics. Onceagain, there is variability in salinity tolerance of

the paspalums, and some selections can surviveirrigation with brackish or even ocean water.However, additional management inputs arerequired when irrigation water contains moderateto high salt levels. In particular, larger quantities ofirrigation water must be available for periodicleaching of salt accumulations out of the root-zone. Buffalograss is ranked as having fair salinitytolerance.

With irrigation restrictions becoming a factof life in more areas of the country, the ability tosurvive drought conditions has become an evenmore important factor in turfgrass selection.Bermudagrass, buffalograss, seashore paspalum,and zoysia get relative rankings of superior, excel-lent, to good as far as their droughtresistance. Avoidance, tolerance,and/or escape are the mechanismsby which turf grasses achieve droughtresistance. Bermudagrass enters intoa dormant stage and thus uses anavoidance mechanism with theonset of drought stress. The brown,off-color character that results isnot aesthetically attractive, but aslong as excessive wear or damagedoes not occur, a turf cover willpersist. Also, with reestablishmentof adequate soil moisture by rainfallor irrigation, a rapid recovery andgreen-up response will occur.Furthermore, it has been observedin the field that the green-up andrecovery response of some of thenew fine-leaf zoysiagrasses is fasterthan bermuda.

With the ability to produce anextensive and deep root system,seashore paspalum is able to utilize moisure fromlower depths in the soil and is an example ofdrought tolerance. However, with the onset ofdrought stress, shoot die-back occurs and turfcoverage and surface quality deteriorate to anunacceptable condition. Excellent root andrhizome survival does allow full recovery, butredevelopment of a good quality turf cover cantake significantly longer when compared tobermuda and zoysiagrass.

Not forgetting about buffalograss, it can persiston as little as two inches of rainfall or irrigationannually. However, attempts to utilize it in thehumid eastern part of the country have met withlimited success because of too much rain.

Even whenmaintained at verylow heights of cut,seashore paspalumcan produce anextensive rootsystem.

NOVEMBER-DECEMBER 2006 3

Fall,early winter, andspring preventivefungicide treatments onfairways can be requiredfor control of zoysiapatch and large patchdisease on zoysiagrass.Large patch disease hasalso been experiencedon seashore paspalum,and while extensive turfloss has not occurred,preventive fungicidetreatments are beingmade. Pest tolerance!resistance is one ofseveral importantselection criteria.

PEST PROBLEMSTo produce and maintain top-quality playingsurfaces in keeping with current golfer expecta-tions, controlling insect, disease, and weed prob-lems is necessary. Yet, pesticide usage on golfcourses has and will continue to be a majorconcern because of perceived and potentialimpacts on the environment. Treatments can alsoadd significantly to annual course operating costs.Clearly, selecting species and cultivars that havepest resistance or tolerance is advisable.

In humid and tropical regions, insect anddisease pressure can be very high. Mole cricketshave long been the number-one pest problem ofbermudagrass-based golf courses in the lower

Southeast and Florida. Without annual insecticidetreatments, significant turf damage and loss willoccur. At the long-running bermudagrass breed-ing program at the Coastal Plains ExperimentStation in Tifton, Georgia, Dr. Wayne Hannafound that there was a consistent pattern of lowermole cricket numbers and reduced damage inTifSport plots compared to the other cultivarsbeing evaluated. This is considered a "nonpreference" characteristic as opposed to resistance.However, on golf courses where TifSport hasbeen used, insecticide treatments for mole cricketcontrol have still been required.

Foliage-feeding caterpillars (army worms andsod webworms), grubs, billbugs, and chinch bugsare some of the other common insect pestsencountered on warm-season golf courses. With

increased use of seashore paspalum on courses inFlorida, it has been found that insect pests similarto those that plague bermudagrass are beingexperienced. This is especially true as far as sodwebworms and army worms. More attention isbeing given to screening for and identification ofinsect resistance mechanisms with all of thewarm-season turfgrasses, and with luck this willpay dividends in the near future.

Plant parasitic nematodes are replacing molecrickets as the number-one pest problem ofFlorida courses. With limitations on nematicidetreatments today and into the future, dealing withthis pest problem is naturally a major concern.Turf resistance to nematodes would be a higWydesirable trait, but it is not an option at this time.Thus, an alternative strategy would be to selectturfgrasses that are able to produce extensive, deeproot systems and also have an aggressive growthhabit that provides increased tolerance to nema-todes. Seashore paspalum and some of the newbermudagrass cultivars have exhibited improvedtolerance to nematodes because of these growthcharacteristics.

Compared to cool-season turfgrasses, thewarm-season species have significantly fewerdisease problems. The aggressive growth habit ofbermudagrass provides tolerance to most diseases,even though fungal pathogens are always present.Very rarely do disease activity and turf damagereach the point that fungicide treatments can bejustified on bermudagrass tees and fairways.Spring Dead Spot (SDS) disease is the exceptionand is considered a major problem on courses inthe transition zone. Identification of tolerant orresistant cultivars is desperately needed.

In the fall, as the growth rate of both zoysia andseashore paspalum naturally begin to slow down,outbreaks of patch diseases have been experi-enced on numerous courses. Large patch(Rhizoctonia solam) and yellow patch (R. cerealis)are the main problems for zoysia fairways, whilelarge patch has been identified on paspalum. Also,dollar spot (Sclerotinia homeocarpa) outbreaks havebeen experienced on paspalum. Preventativefungicide treatments in the fall are being recom-mended for control of patch disease problemsthrough the winter and spring and until sustainedgrowth resumes. With seashore paspalum,improper nitrogen fertilization and irrigation cancontribute to increased patch disease incidence,but it should be pointed out that no cases ofdevastating turf damage and loss have been


reported. Nevertheless, the disease problems thathave been experienced to date and increasedfungicide usage are concerns.

A very dense turf is a key component mini-mizing weed invasion, and this is a commoncharacteristic of zoysiagrass, seashore paspalum,and bermudagrass. There are, however, severalopportunistic and highly invasive annual andperennial weeds that can become established in allwarm-season turfgrasses. Thus, herbicide treat-ments are needed to maintain acceptable levels ofweed control, and with both zoysia and bermuda,an adequate arsenal of pre- and post-emergentmaterials is available. The list of options for sea-shore paspalum is also growing.

The superior salinity tolerance of seashorepaspalum also makes topical applications of salt aweed control option. Directly applying rock saltor spraying ocean water on weeds can provideacceptable control of a number of problemspecies. However, this strategy has not workedsatisfactorily for controlling bermudagrass infes-tations in paspalum. Nor are there any selective

herbicides currently available that provide goodcontrol! suppression of bermudagrass without alsocausing unacceptable damage to the paspalum.Most golfers do not recognize this weed problem,and thus it can be debated as to whether or not itis a truly significant problem. However, at least inFlorida, a lot of time and effort are being devotedto bermudagrass control.

FERTILITYREQUIREMENTSFertilization is a basic and necessary turfgrass andgolf course management practice. However, aswith pesticides, potential negative impacts ongroundwater and/or surface water supplies aremajor concerns with fertilizer usage. Fertilizer canalso be one of the bigger line items in the annualoperating budget for a course. Thus, a lowfertilizer requirement is a highly desirable charac-teristic. Bermudagrass has a relatively highfertilizer requirement, and in the past excessivenitrogen applications were unfortunately all toocommon in an effort to produce a darker green

A classic case ofbermudagrass winterkill.Replanting with a morecold-tolerant cultivarcould help minimizerecurrence of thisproblem.


Lack of a selectiveherbicide to controlbermudagrassinfestation inseashore paspalum isa problem, especiallywhen convertingfrom one speciesto another.

color. Bermuda cultivars are now available thatperform satisfactorily with lower fertilizer inputsand also have a more aesthetically pleasing colorcharacter.

Seashore paspalum is extremely efficient as faras nitrogen utilization is concerned, even oninfertile, sandy soils; fertilization requirements canbe less than half of what is required for bermuda-grass. Zoysiagrass also requires less fertilizationcompared to bermuda, but it has been found thatthe new, finer-leaf cultivars require more nitrogenthan older cultivars.

COLD TOLERANCEThroughout the transition zone of the UnitedStates, cold tolerance is a critically importantselection factor with warm-season turf grasses.Even in the mid to lower South, where theground does not freeze for extended periods oftime, periodic winter kill of bermudagrass canoccur. This and its brown color when it isdormant have been limiting factors in its use.Excellent strides have been made in the develop-ment of more cold-tolerant bermudagrasses,increasing its range further north in thetransition zone.

The cold tolerance of seashore paspalum issimilar to that of bermudagrass, but further evalu-ation of this characteristic is also needed. In areassuch as Central to South Florida, where bermuda-grass does not go fully dormant and brown,

paspalum maintains a greener color, very similarto a winter overseeding cover. Yet, cart traffic andwear damage problems similar to what is experi-enced with bermuda can occur when moderateto heavy play is hosted. It has also been found thatseashore paspalum transitions out of overseedingsmootWy and better than bermudagrass.

Zoysiagrass has better cold tolerance relative tobermudagrass. This and its ability to maintain agreener color character longer into the fall arefactors in its increased use. Yet, once again, varia-bility in cold tolerance occurs among the zoysias,and some of the new fine-leaf types have signifi-cantly reduced tolerance compared to Meyer andEmerald.4 Furthermore, good drainage, minimalshade, and proper management playa role inminimizing the potential for winter kill with allwarm-season turfgrasses.

SUNLIGHT REQUIREMENTSAll plants require sunlight for photosynthesis andgrowth, and as a group the warm-season turf-grasses have a high light requirement. Lack ofshade tolerance has long been recognized as amajor limiting factor with bermudagrass, andeight hours of direct sunlight is considered theminimum requirement for sustained healthygrowth. Seashore paspalum was initially thoughtto be very similar to bermuda as far as its toler-ance to tree shade. It has been found, however,that paspalum is persisting and performing satis-


BuffalograssI I 'I

Zoysiagrass

Bermudagrass

Table ISummary and Comparison of Relative

Salinity Tolerance to Wat~r ,Usage RatesSeashorePaspalum

Fair

Good

Superior

Excellent

factorily in shaded locations where bermudafailed. Paspalum is also more tolerant to periods ofreduced sunlight intensity due to heavy, persistentcloud cover.

Zoysiagrass has moderate shade tolerance, andin the past it has been used as an alternative tobermuda. Development of more bermudagrasseswith shade tolerance has been a goal of somebreeding programs, and there are commerciallyavailable cultivars now available that have per-formed as well as, if not better than, zoysia inshaded locations.

, 10 II 12234oPoor

Water Usage Based on Mean Summ~rE"fRate (mmd")" I

appealing to most golfers. Furthermore, mowerstriping patterns are more pronounced with bothpaspalum and zoysia compared to bermuda. Thecombination of these characteristics results in anaesthetic "WOW factor" that is being heavilyweighted in the selection process.

Hybrid bermudagrasses, seashore paspalum,and the fine-leaf zoysias all have a very dense andupright shoot growth character, providing anexcellent tee and fairway surface condition. The"stiffer" leaf of paspalum and zoysia also providesgreater ball support so that it sits right on top ofthe turf surface. Some, but not all, golfers like thevery tight and firm fairways that can be produced.There are also distinct differences in the playcharacter of the putting green surrounds androughs of the warm-season grasses, but that's atopic for another time.

With regard to warm-season putting surfaces,the old standard ofTifdwarf is not a bad grass;with the tools available today, appropriate andgood quality conditioning for daily play can beprovided. However, the ultradwarf cultivars haveraised the bar as far as the level of conditioningand quality that can be provided. As a result, thereis no longer the push to try to maintain bentgrassputting greens in hot and humid regions where itis not adapted to survive on a year-round basis.The ultradwarfs are certainly not bullet proof, butalong with being better adapted for meeting cur-rent golfer demands, they have exhibited a morestable performance character compared to Tif-dwarf. There is a consensus opinion that the ultra-dwarfs have replaced Tifdwarf as the standard.

OTHER CONSIDERATIONSGoing beyond the basic factors that affect warm-season turf grass growth, establishment rate, weartolerance, and recuperative ability are characteris-tics that need to be considered in the selectionprocess. Until recently, the best quality cultivarswere vegetatively propagated, and thus sprigs orsod has been used for establishment. Whenenvironmental conditions are favorable to sustainactive growth in the summertime, both bermuda-grass and seashore paspalum have a very rapidestablishment rate. A full turf cover and appropri-ate conditions can be developed in as little as 8-12weeks after sprigging. If poor quality irrigationwater must be used during the grow-in process,however, the rate of paspalum establishment willbe significantly slower. A number of seededbermudagrasses are now available that have com-parable quality to the vegetative hybrids and, ingeneral, their establishment rate is similar. Zoysiaestablishment from sprigs is slow, and thus strip orsolid sodding has typically been employed despitethe additional cost.

As a group, bermudagrass, seashore paspalum,and zoysiagrass have very good wear tolerance.The aggressive growth habit of bermuda alsoprovides it with good recovery from damage.Paspalum has good recuperative ability as well,but its recovery from mechanical damage such asmower scalping and drought stress can be quiteslow. The inherently slow growth rate of zoysia-grass is a problem as far as recovery from damageis concerned.

Aesthetics and play characteristics are two otherfactors that must be considered. From the purelyagronomic standpoint, color is a minor considera-tion, but American golfers expect and demandlush green playing surfaces. Both seashorepaspalum and zoysiagrass have a "greener" colorcompared to bermuda, and this color is very


REFERENCES1.Baldwin, C. M.; Liu, H.; McCarty, L. B.; Bauerle, W L.;

Toler,). E. 2006. Response of six bermudagrass cultivars todifferent irrigation intervals. HortTechnology. july-September. 16(3):466-470.

2. Beard, james. 1973.Turfgrass Science and Culture. p. 132.Prentice-Hall, Inc., Englewood Cliffs, N.J.Beard,james B. 2002. Turf Management for Golf Courses.p. 27.Wiley & Sons, Inc., Hoboken, N.J.

3. Carro\v, Robert. Seashore Paspalum Ecotype Responses toDrought and Root Limiting Stresses.USGA Turfgrass andEnvironmental Research Online 4(13):1-9. TGIF RecordNumber: 105521.

4. Carrow, Robert. What We Know About The New Zoysia-grasses.North Carolina Turfgrass. Summer, 1995.

Similar to Tifdwarf, appropriate and goodquality conditioning can be produced with sea-shore paspalum putting greens. However, main-taining a consistent putting speed through the dayand keeping speeds comparable to the ultra dwarfshave become concerns at some facilities. Growthregulator treatment programs can help, but at thistime, mowing and rolling inputs are much higherrelative to what is conducted with bermuda greens.

Finally, with comparison of a number of theselection factors discussed in this article, seashorepaspalum and zoysiagrass have advantages overbermudagrass. Absolutely, if a poor quality salineirrigation water source is a factor, paspalum is alogical choice. Also, the cold tolerance of zoysia-grass favors its use in the most northern portionof the transition zone. However, in regions wherebermudagrass is well adapted and has performedsatisfactorily for many years, it would be urgednot to put too much emphasis on the aesthetic"WOW" factor. With both paspalum and zoysia,mowing and cultural management requirements,increased equipment maintenance costs, andhaving to conduct large-acreage preventive fungi-cide treatments can negate cost savings achievedin other areas.

For assistance in selecting the right grass, thelogical starting points are the National TurfgrassEvaluation Program (NTEP) and state universitytrials in a similar climatic zone. The Green Sectionregional agronomists are also an excellent sourceof unbiased information on species and cultivarperformance on area courses. While not always anoption, on-site evaluation is strongly encouraged,and at least two to five years needs to be allowedto gain a good understanding of performance andmanagement requirements.Ranking

Excellent

5-73.1-73.8-93-9

3.5-87-8.57-8.57-8.56-8.56-8.5

3.3-6.96.6-11.28.8-108.5-10

3.6-12.65-10>10

4->10>10

Table 2ry of Mean Rates of Turfgrass Evapotranspiration

,- - - 1) j

JOHN Foy has spent more than 20 years helping golfcourses select the right warm-season twigrasses.


selecting the right grass selecting the right grass with many warm-season turfgrass options...

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