Just as the game of golf has evolved over the years, putting green turfgrasses have changed significantly with time and technique. An example of this evolution is ultradwarf bermudagrass. Born out of the desire for faster, firmer, and more consistent putting surfaces, ultradwarfs entered golf’s picture only about 25 years ago and are now the fastest growing variety of putting green grasses in warm season and transitional locations.
The History of Ultradwarfs
The short history of ultradwarfs begins with the bermudagrass Tifgreen, released in 1956. This breakthrough turfgrass owes its origins to Dr. Glenn Burton, who used USGA funding to cross-pollinate African and common bermudagrasses, producing a hybrid with traits that set the new standard for greens. Tifgreen’s drawback – and lasting legacy – was its prolific tendency to mutate genetically, creating new and varied plants, many with appealing characteristics for putting greens.
James B. Moncrief, director of the USGA Green Section’s Southeast Region at the time, collected a naturally occurring mutation of Tifgreen that became Tifdwarf. Released in 1965, Tifdwarf possessed a darker green color and the ability to tolerate lower mowing heights.
This pattern of development continued for some thirty years before the first ultradwarfs premiered. The 1990s saw the introduction of the varieties that continue to be today’s major ultradwarf stars. MiniVerde and Champion were both selections from naturally occurring mutations in Tifgreen, and TifEagle was created from the process of mutation breeding.
All three possess characteristics that established even higher standards for putting green quality. Finer leaf blade, greater density, increased upright growth, and tolerance for still lower heights of cut differentiated ultradwarfs from their predecessors and delivered smoother, firmer, and faster greens.
Selecting among the ultradwarf choices for new and renovation projects requires consideration of multiple variables. Climatic conditions, geographic location, shade, and water supply all matter, as do the maintenance budget and superintendent skill level. Realistic assessments of these factors need to be combined with a clear understanding of the benefits and limitations of the varieties. TifEagle is the most popular of the ultradwarfs and boasts the best shade tolerance of the three, but produces more grain and is the least cold tolerant. Champion has a high-density shoot growth pattern, which results in an excellent putting surface, but has a more shallow root system causing problems for turf managers during times of stress. Champion also performs less than optimally on greens with heavier organic content. MiniVerde tends to have the deepest roots and the fastest green speeds but is not especially shade tolerant.
An ultradwarf concern affecting all three varieties is the possibility of mutations and off-types. This issue should not be a surprise considering that all ultradwarfs are the product of mutations, either naturally occurring or through mutation breeding. Some off-types produce little or no effect and fail to thrive due to low heights of cut and other maintenance practices. However, many off-types create concerns through noticeable differences in color, growth rate, or texture compared to the original turfgrass.
As ultradwarf varieties matured and off-types emerged, attention began to increase. Dr. Jim Brosnan, turfgrass weed scientist at the University of Tennessee and his graduate assistant Eric Reasor launched a study of the problem.
“Considering the amount of ultradwarf grown in the Southeast and its increasing demand, this is a good place to focus research,” said Reasor. “Off-types are a fundamental weed management problem.”
Collecting over 50 off-type samples from 21 golf courses across the Southeastern United States, the team included sources of every type: old and new greens, renovations and new designs, intensive and minimal management programs, and varying maintenance budgets. Results showed that all of the off-type samples were within the Tifgreen-derived cultivar family, and none of their particular samples were cross-contaminants from other areas of the golf course.
“All ultradwarf varieties exhibit various forms of self-contaminated off-types,” Reasor said. “Ultradwarfs were derived from mutations themselves, and no variety is immune to off-types.”
Accurately sourcing the origin of off-types (contamination in the production field; on-site contamination from collars, roughs, or fairways; or genetic mutations developing on-site) is not simple, but precautions can be taken. At the onset of a project, buying turfgrass from quality sources with a proven record of providing clean material is key. Reasor also recommends visiting production fields as well as courses that have grown the desired variety for some years.
For projects where off-types are occurring, the second part of Brosnan and Reasor’s research comes into play.
“We are looking at off-type responses to growth regulators and nitrogen, both commonly used to manage putting greens,” said Reasor. “By studying rates and dosages and preferable management practices, our goal is to provide superintendents, architects and the entire turfgrass industry with solid data and research-based strategies to successfully manage off-types.”
The Newest Ultradwarf
The quest for ever better quality and easier managed putting greens continues. The newest commercially available ultradwarf bermudagrass is gaining popularity. Sunday Ultradwarf Bermudagrass was selected for its dense growth canopy, lighter color, and reduced seed heads. NTEP trial results show positive advantages in establishment, ball roll, fall color retention, and recovery from injury.
Shannon Easter, director of golf maintenance and environmental consultant at The Broken Sound Club in Boca Raton, Florida, became familiar with Sunday long before its commercial release. In 2003, he joined Craft Farms in Gulf Shores, Alabama, where the Sunday greens were already 18 years old. In his seven years there, he did not experience a single mutation.
“During my career, I’ve managed Tifgreen, TifEagle, Champion, Tifdwarf, and Floradwarf greens,” said Easter. “Sunday greens were the first in my experience where I did not see mutations.”
Moving to Broken Sound in 2012, Easter wanted to see if Sunday would perform as well in South Florida. He planted a large test green last summer and implemented identical maintenance practices as the club’s two courses featuring TifEagle.
“Sunday outperformed TifEagle in cool season color, height of cut, and green speeds and has two-thirds more root mass,” said Easter. “Sunday also recovers better from verticutting and aerification, and requires less fungicide.”
Based on the test results, Easter will lead Broken Sound in the conversion to Sunday greens on its Club Course in 2018.
As ultradwarfs continue to advance and research brings about more effective maintenance practices, opportunities for ever-improving golf greens do not end. The evolution continues.
John Holmes, president of Atlas Turf International, has worked in the golf and turf industry for over 25 years. He assists clients around the world with turfgrass needs for golf course and sports field projects.