The putting green is the most intensively managed area on any golf course. This turf must provide an ultra-smooth, dense surface that allows a golf ball to roll predictably and at high speed. Achieving this requires specialized grass species capable of surviving extreme stress, primarily from being mowed to ultra-low heights, often below one-eighth of an inch. The turf must possess a fine leaf texture and a high shoot density to form a tight, uniform carpet.
The selection of turfgrass is an agronomic decision based on the local climate and performance requirements. Only a few species can tolerate such intense management while providing a consistent, true roll. These grasses must also recover quickly from the daily wear of foot traffic and ball marks.
Primary Cool-Season Grasses: Creeping Bentgrass
Creeping bentgrass (Agrostis stolonifera) is the traditional choice for golf greens in regions with cool summers and cold winters. This cool-season species spreads aggressively via above-ground stems called stolons, forming an extremely dense, uniform turf canopy. This stoloniferous growth habit provides excellent recovery from damage, which is necessary for a surface subjected to daily use.
The grass is valued for its exceptionally fine leaf texture and its ability to withstand consistent mowing heights as low as 0.100 to 0.125 inches. Modern cultivars, such as the Penn A-series (A-1, A-4) and Penncross varieties, have been developed for enhanced performance under stress. These newer varieties exhibit superior shoot density and an upright growth habit, which helps minimize the undesirable “grain” that can affect ball roll. Creeping bentgrass thrives in moderate temperatures, making it a reliable surface throughout the primary growing season in northern latitudes.
Primary Warm-Season Grasses: Ultradwarf Bermudagrass
In warm and tropical climates, the preferred species is a specialized hybrid of bermudagrass (Cynodon species) known as ultradwarf bermudagrass. These varieties, such as ‘TifEagle,’ ‘Champion,’ and ‘MiniVerde,’ are mutations selected for their ability to tolerate extreme heat and intense management. Their aggressive growth is a major advantage, allowing them to repair damage quickly in high temperatures where bentgrass would fail.
Ultradwarf varieties possess a finer leaf blade and a higher shoot density compared to older bermudagrass hybrids, creating a putting surface comparable to bentgrass in smoothness. These grasses are maintained at similar low heights of cut, often between 0.100 and 0.125 inches, to achieve the desired green speed. The primary challenge is its dormancy period, where it turns brown and stops growing entirely in cooler winter months. This winter vulnerability often necessitates the use of specialized turf covers to prevent freeze damage or the temporary overseeding of a cool-season grass like annual ryegrass for winter play.
Key Factors Influencing Turf Selection
The initial decision between bentgrass and bermudagrass is governed by clear geographic boundaries that define three distinct climate zones. The Cool Zone, encompassing the Northern United States, Canada, and parts of Europe, favors creeping bentgrass due to its cold tolerance. Conversely, the Warm Zone, which includes the Southern United States and tropical areas, relies exclusively on the heat tolerance of ultradwarf bermudagrass.
The Transition Zone, a large band across the middle of the continent, presents the most difficult challenge. It is too hot for bentgrass in summer and too cold for bermudagrass in winter. Courses in this zone must implement highly specialized, season-specific management programs to keep the turf alive year-round, including intensive soil temperature monitoring and the use of protective covers in winter for bermudagrass greens.
Maintenance Intensity
Maintenance intensity differs significantly between the two primary grass types. Bentgrass requires frequent fungicide applications to combat diseases like dollar spot and brown patch, especially during summer stress periods. It also benefits from deep, infrequent irrigation to encourage the development of a deeper root system.
Ultradwarf bermudagrass, due to its vigorous growth, necessitates aggressive cultural practices to control the turf’s density and prevent a negative effect on ball roll called “grain.” Superintendents must routinely perform vertical mowing (verticutting) and apply plant growth regulators (PGRs), such as trinexapac-ethyl, to suppress vertical growth and maintain a tight, upright leaf structure.
A persistent factor in turf selection is the presence of Poa annua, or annual bluegrass, which is technically a cool-season grass often considered a weed. It frequently invades and colonizes older bentgrass greens, particularly in the Transition Zone and Cool Zone. Although it can provide a high-quality surface, its shallow root system makes it extremely vulnerable to heat and drought stress. Superintendents must decide whether to suppress its encroachment through selective herbicides and reduced nitrogen use, or to manage it as the primary, fragile putting surface.