VARIATIONS ON A GREEN... Finding the Best Bermudagrass for Alabama Putting Greens

Evaluation of the bermudagrasses includes such measurements as thatch depth, rooting depth, and rate of growth.

Elizabeth A. Guertal, R. Harold Walker, Ray Dickens, and Coleman Y. Ward

Golf is a billion dollar industry in the United States, and the popularity of the game shows no signs of slowing down. The Southeast, in part because its warm climate attracts retirees and vacationers, has become a popular golfing region, and quality courses have become a hallmark of many southern towns. However, increased competition for a golfer's dollar means that golf courses must be well-maintained, challenging, and well-groomed.

Although many courses pride themselves on creeping bentgrass putting greens, bentgrasses are cool-season grasses adapted to the northern United States. The hot, humid climates of the Southeast can exert a toll on creeping bentgrass greens, and their putting quality may decline rapidly as temperatures rise during the summer.

Hybrid bermudagrasses are the best adapted grasses for putting greens in warm, humid regions because they have superior heat tolerance and persist well under low mowing heights. However, only a limited number of bermudagrass cultivars with turf quality similar to bentgrass have been identified or developed for use on putting greens.

In 1994, AAES researchers began a study to identify new bermudagrasses for use on southern putting greens. The study evaluated both cultivars and ecotypes.

A cultivar is a “cultivated variety”—one that has been selected through breeding, evaluation, and research as a superior type. Ecotypes, or variants, are usually first observed as an “off-type” when certain plants within a cultivar demonstrate growth or appearance different from the normal cultivar.

Two bermudagrass cultivars developed for golf greens are Tifgreen and Tifdwarf, both released from turf breeding programs at the Georgia Agricultural Experiment Station. Tifgreen was released first and, soon after its release, distinct off-types appeared in Tifgreen putting greens throughout the Southeast. Of these off -types, Tifdwarf was identified and later released as a cultivar and has become established in the turf trade. However, there is evidence that other off-types also exist, and turf managers continually report the occurrence of variants within Tifdwarf and Tifgreen putting greens.

To learn mroe about the potential of these cultivars and ecotypes for putting greens, researchers evaluated grasses on both native soil and United States Golf Association (USGA) putting greens. Native soil is soil that is found naturally at the putting green location and has not been amended with sand or foreign soils. The USGA greens are typically constructed of approximately 80-90% sand and 10-20% organic amendments.

Sprigs (stolons) of Tifgreen, Tifdwarf, their ecotypes, and other bermudagrass cultivars were collected from golf course greens and turf breeders from across the Southeast (see table). Among the grasses evaluated were ecotypes collected from two greens on the Country Club of Mobile (Azalea City) golf course, one from The Gulf State Park golf course in Gulf Shores, two new bermudagrass cultivars from the Georgia Agricultural Experiment Station (T596 and TW72), and two African bermudagrasses from Oklahoma State University turf breeding program.

Grasses were planted on April 14, 1994, in the USGA and native soil greens in replicated strip plots located at the Auburn University Turfgrass Research Unit in Auburn. All plots were maintained as a putting green, with daily mowing at a 3/16-inch height. To keep the putting surface continually green, the plots were overseeded with rough bluegrass in the fall as the bermudagrass became dormant.

Plots were evaluated for rate-of-cover during the grow-in period. Rate-of-cover is important because plots that establish quickly can be opened for play sooner. The grasses also were evaluated for fall color, fall seedhead production, spring greenup, and spring seedhead production. Color is important because golfers desire a green appearance, and over-abundant seedhead production is an undesirable trait because seedheads are unsightly and affect the putting quality of the green.

During the grow-in period, the only significant difference in rate-of-coverage was due to the type of putting green rather than the bermudagrass cultivar or ecotype. When averaged over all grasses, percent turf cover on May 19 in the native putting green was 74%, compared to 56% average cover observed on the USGA putting green. This difference was still observed on June 21, when percent cover was 96% and 85% for the native and USGA putting greens, respectively.

Differences in rate of establishment on USGA and native soil putting greens may be caused by many factors, including soil moisture and/or fertility. Additional studies are planned to examine factors that affect rate of grow-in on USGA and native putting greens.

Bermudagrass grown on the USGA putting green was usually darker than grasses grown on native soil. The two Oklahoma bermudagrasses were lighter green than other entries. The cultivars Tifdwarf, T596, and the Tifdwarf ecotype from the Mobile Country Club (Number 10 green) were greener than other grasses. Unfortuantely, the Mubile country club ecotype was the only grass to produce a profusion of seedheads in the fall.

More grasses produced seedheads in the spring, and there were more seedheads produced on the USGA green than the native soil putting green. Two grasses never produced seedheads - an ecotype selected from the Number 9 green of the Mobile country club and the Georgia cultivar TW72.

When all factors are examined, the new bermudagrass cultivar TW72 shows excellent promise as a bermudagrass for putting greens. Of selected ecotypes, the best performance was demonstrated by selections from a Gulf Shores course and the Number 9 green of the Mobile country club.

Additional cultural treatments of mowing height and traffic intensity will be superimposed on the main blocks of grasses, allwowing further evaluation of the ecotypes and cultivars in stress situations.

*This research is funded in part by the United States Golf Association, the Alabama Turfgrass Association, and the Alabama and Gulf Coast chapters of the Golf Course Superintendents Association.

Guertal is an Assistant Professor, Walker is a Professor, and Dickens is a Professor Emeritus of Agronomy and Soils. Ward is a Professor Emeritus of Horticulture.