Managing Off-Types in Bermudagrass Putting Greens: A Comprehensive Guide

Key Takeaways

“Off-types” in bermudagrass putting greens come from phenotypic variants or genetic mutations of the planted variety, or from contamination that can occur at the turf farm or after the grass has been planted at the course.
Off-types can cause unpredictable ball roll, scalping and visible patchiness, increasing maintenance demands and decreasing golfer satisfaction.
Certified planting materials, rigorous equipment sanitation, clean topdressing sand and precise edging are essential to prevent off-types from establishing.
Regular scouting for color, texture and growth anomalies enables early intervention to limit the spread and severity of off-type infestations.
Spot treatments with nonselective herbicide, physical removal, selective use of plant growth regulators (PGRs) and carefully balanced nutrition are all part of off-type management.
Regrassing becomes the best solution if off-types dominate more than 20%-30% of a green or severely disrupt play. Successful regrassing requires thorough eradication of old turf and meticulous grow-in practices.

Bermudagrass putting greens are widely celebrated for their exceptionally smooth ball roll, vibrant visual appeal and remarkable resilience to high-intensity play demands. These qualities make them the preferred putting surfaces for most golf courses in warm-season climates. However, a challenge that many golf course superintendents encounter when managing bermudagrass putting greens is the emergence of “off-types,” which are typically an unwanted bermudagrass variety or a spontaneous genetic mutation or phenotypic variant of the desired grass. These off-types compromise the uniformity of the putting surface, leading to inconsistencies in ball roll, diminished aesthetic quality, increased maintenance demands and unhappy golfers. Gaining a thorough understanding of the causes behind off-type issues and implementing proactive, science-based management strategies is essential for preserving bermudagrass putting greens' integrity, performance and long-term quality.

What Causes Off-Types on Putting Greens?

Off-types in ultradwarf bermudagrass putting greens are often the result of genetic or physiological changes that occur over time, even in turf established from a single clonal cultivar. The bermudagrasses typically used on putting greens are propagated vegetatively, but small genetic changes – known as somatic mutations – can develop within individual plants. When these mutations give rise to traits such as faster growth or different leaf textures, the resulting off-types can become more competitive than the original cultivar and spread throughout the greens. Stress such as heat, drought or management practices may further influence how these off-types express themselves by triggering shifts in growth patterns, appearance or physiology (Caetano‐Anollés et al., 1997; Goatley et al., 2003). This ultimately produces patches that deviate in appearance and/or performance from the surrounding turf.

Contamination refers to the accidental introduction of unwanted grasses into the green, which can happen through multiple channels. Sod or sprigs used to grass the greens may unintentionally contain various grass types; unwanted grasses can also be transported into the greens via natural causes or on maintenance equipment that hasn’t been adequately cleaned. Once introduced, these contaminants can establish themselves and spread, creating a patchwork of turf varieties that disrupt the uniformity of the green.

Impact on Playability and Presentation

From a playability standpoint, off-types can significantly disrupt the smooth, predictable ball roll players expect. Variations in growth rates, leaf textures and shoot densities among different grass types create inconsistencies across the putting surface, leading to unexpected bounces, inconsistent roll and overall player frustration. This lack of uniformity demands heightened attention to detail from superintendents and often requires specialized interventions such as fine-tuning mowing heights, applying targeted growth regulators, and making spot treatments with nonselective herbicides to maintain surface integrity.

Visually, off-types manifest as discolored, irregular patches that disrupt the uniform canopy. Such blemishes not only diminish the aesthetic quality of the green but may also raise concerns about the standard of turf management. The greens may roll great, but they look inconsistent so that is how they are perceived. While a “mottled” look is common and accepted at courses with cool-season greens, an inconsistent appearance is often perceived as a flaw on bermudagrass greens. The visual and playability impacts of off-types are often most pronounced as growth accelerates in late spring and early summer, and then again as growth slows in the fall. This is because the desired variety and the off-types react slightly differently to changes in growing conditions.

The emergence of off-types may point to underlying issues with your maintenance program. If you start seeing off-types on your greens, it’s important to make a comprehensive evaluation of the overall maintenance program to see if you can make any adjustments that will keep the issue from getting worse. It can be tempting to blame mutations, but be honest with yourself about whether aspects of your maintenance practices may be causing contamination that you can eliminate in the future. Addressing these issues proactively is essential to preserving the integrity of the greens.

Preventing Off-Types: Proactive Management Strategies

Preventing the establishment of off-types is always preferable to managing them after they appear. The first and most critical line of defense is to source high-quality, certified planting material when grassing greens. Whether using sod or sprigs, superintendents should only buy from reputable producers who can guarantee varietal purity. Visiting production sites and requesting documentation of genetic testing can provide additional assurance. Beyond the initial planting, equipment sanitation plays a crucial role. Mowers, aerators, topdressers and any other equipment that comes into contact with turf should be thoroughly cleaned after working in areas that contain grasses you don’t want on the greens. Even a small amount of debris can introduce off-types that may establish and spread. Equally important is the practice of precise edging, which is often the most effective line of defense against encroaching turfgrasses infiltrating the putting green perimeter. This practice is typically performed on a weekly or biweekly basis during the active growing season, and monthly during periods of reduced growth. Greens must be separated from collars and approaches when these surrounding areas contain different turf varieties. Using physical barriers, mechanical edging or carefully applied herbicides can help preserve these boundaries.

Attention must also be paid during aeration and topdressing. While vital for turf health, these practices can inadvertently introduce and spread off-types if not executed carefully. Sand used for topdressing should be clean and sourced from uncontaminated stockpiles. Aeration equipment should be free from debris that could carry seeds or plant matter from other areas. Additionally, soil or sand from mixed-variety areas should never be applied to greens. Routine scouting of the greens is also essential. Superintendents and their teams should regularly inspect for early signs of off-types, such as subtle shifts in texture, growth rate or color. Early detection allows for targeted interventions and reduces the likelihood of widespread contamination. Once a small area of an off-type is present within a green, routine maintenance can quickly spread it throughout that green and onto others. Train staff to routinely monitor for:

Color variation (lighter green or bluish tints)
Texture differences (coarse leaves, more-upright growth)
Growth rate anomalies (faster vertical growth or lateral spread)

Map and photograph suspected off-type areas to track changes over time. Drone photos can be a great tool for this purpose. Early identification allows for selective treatment before the off-types get out of control.

Managing Off-Types Once Present

Despite best efforts, off-types may still establish on putting greens. When this happens, various management strategies are available to minimize their impact. Spot treatments with nonselective herbicides can be effective for addressing localized infestations. This approach requires precision to avoid damaging desirable turf, but it allows you to kill the unwanted grass and then replace it by plugging or sodding with the preferred bermudagrass cultivar. Physical removal is efficient for larger or more-persistent patches. Techniques like sod cutting or plugging can excise the affected areas entirely, allowing for replacement with the desired turf. When removing an area contaminated with an off-type, you want to dig deeper than normal sod cutting to remove subsurface roots and rhizomes that could lead to a return of the problem. I recommend removing 4-5 inches of the putting green soil profile, including the turf, when addressing areas infested with off-types. To ensure complete removal, the target area should extend at least 6 inches beyond the visible off-type to capture any spreading stolons or rhizomes. If removal is not practical, plant growth regulators (PGRs) can be used to suppress off-type growth and fertility programs can be adjusted to favor the desired cultivar.

On-Site Putting Green Nursery

Maintaining an on-site putting green nursery is an important part of managing off-type contamination. A nursery green provides superintendents with a readily available, genetically consistent source of the desired bermudagrass variety, which is essential for efficiently replacing contaminated areas. When off-types are detected, access to a nursery allows for rapid sod or plug replacement, which minimizes the risk of spread. Furthermore, using in-house nursery material ensures consistency in genetic traits and performance characteristics, which may not always be guaranteed when sourcing from external suppliers. Beyond off-type management, a nursery green also serves as a vital resource for refining maintenance practices, testing new products and training staff. An on-site nursery is well worth the investment.

Plant Growth Regulators

Plant growth regulators are essential tools for managing off-types in bermudagrass putting greens. By selectively suppressing the vigor of more-aggressive or faster-growing off-type grasses, PGRs give the desirable turf a competitive advantage while helping maintain surface uniformity and smoothness. However, their effectiveness depends heavily on precision. Misapplication or overuse can unintentionally enhance off-type expression or lead to turf stress; therefore, careful calibration based on growth patterns, turf response and environmental conditions is crucial. Among the most commonly used PGRs for this purpose are trinexapac-ethyl (Primo Maxx), prohexadione-calcium (Anuew) and paclobutrazol (Trimmit), each with a distinct mode of action and suppression profile. A widely used and effective starting combination for off-type regulation includes Primo at 2 ounces per acre and Anuew at 4 ounces per acre. These rates can be adjusted based on turf tolerance, weather conditions and the desired degree of suppression. When applied thoughtfully, PGRs not only suppress unwanted growth habits but also contribute significantly to the visual and functional consistency of putting surfaces.

Fertility Considerations

An optimized nutrition program is a critical element of managing off-types in bermudagrass putting greens. A well-balanced fertility strategy enhances the health, vigor and density of the desired cultivar, giving it a competitive edge over off-types. At the same time, both over- and under-fertilization can be detrimental to surface consistency. Excessive nitrogen can lead to thatch buildup, excessive vertical growth and weaker turf, all of which create favorable conditions for off-type encroachment. On the other hand, insufficient fertility reduces turf vigor and density, making it easier for off-types to establish and spread.

To maintain precision and consistency, nutrient applications should be guided by soil testing and tissue analysis. Particular emphasis should be placed on balanced nitrogen inputs and adequate micronutrient availability throughout the growing season. A low-nitrogen approach is generally recommended for ultradwarf bermudagrass greens, especially when off-types are present. Applying between 0.1 and 0.2 pounds of nitrogen per 1,000 square feet per application, with monthly totals not exceeding 0.2 to 0.4 pounds, is typically effective. These lower rates are best delivered through biweekly foliar sprays or light granular applications to promote steady growth without encouraging off-type dominance.

High nitrogen rates, particularly those exceeding 0.5 pounds per 1,000 square feet in a single application, should be avoided. Such rates often trigger rapid, uneven growth and can intensify the visual and physical differences between the desired cultivar and off-type patches. Preferred nitrogen sources include foliar urea or ammonium sulfate, both of which offer quick uptake and allow for precise control. Slow-release granular products, such as methylene urea, can be beneficial in cooler months or shoulder seasons when turf uptake is more gradual; however, they should be used sparingly when off-types are a concern.

Ultimately, nutrition is not just about promoting growth; it is a key tool in the broader strategy of maintaining uniformity on the putting green. When used in tandem with PGRs and surface management practices, a dialed-in fertility program can help superintendents limit off-type expression and maintain putting green quality and consistency.

When To Consider Regrassing and How To Ensure Success

Depending on the golfers’ preferences and the severity of the off-type issue, there may come a point when spot treatments and cultural practices are no longer sufficient. Based on experience, when off-types have overtaken more than 20% to 30% percent of a putting green, or when differences in growth habit, texture and color are too pronounced to manage, regrassing becomes the most practical solution. Although this is a significant undertaking, it can restore consistency, improve long-term playability, and ultimately reduce the maintenance burden that comes with managing patchwork turf.

Choosing to regrass involves several critical considerations. First and foremost is selecting the appropriate variety. The chosen bermudagrass cultivar should exhibit genetic stability, strong performance characteristics and resistance to common mutations. It must also be well-suited to the region’s climate and the facility's maintenance practices. While popular cultivars like ‘TifEagle’, ‘MiniVerde’ and ‘Champion’ remain widely used, newer selections like ‘Tif3D’ and ‘Mach 1’ may offer improved performance and fewer off-type issues. Once a variety has been selected, verifying the quality and purity of sod or sprigs is essential. This often means visiting the sod farm before delivery, visually inspecting the material and requesting genetic purity tests.

Equally important is the process of eliminating the existing turf. A thorough and patient kill phase is crucial. Nonselective herbicides should be applied across the entire green, followed by a waiting period to allow regrowth, followed by two or three subsequent nonselective herbicide applications. Rushing this phase can result in lingering contamination that undermines the success of the regrassing effort.

After the herbicide treatments are complete, I recommend removing at least 4 inches of the existing rootzone mix, including the turf, to eliminate the old turfgrass and its root structure effectively. This is an ideal opportunity to remove accumulated organic matter and either replace it with a fresh sand/peat mixture or replant the new turf directly onto the remaining greens mix, provided that at least 12 inches of rootzone material remains if the greens were built according to USGA recommendations. Modern surveying equipment allows courses to preserve or adjust the putting green contours at a lower elevation if desired. If you are going to establish the greens at a new elevation, stripping and regrading the surrounds will be necessary to properly tie in the new putting surfaces. Testing soil for pH and nutrient levels ensures that it is conducive to establishing new turf. The surface should be smoothed and leveled carefully prior to planting to promote even growth and consistent play once the turf is established.

Conclusion

Managing off-types in bermudagrass putting greens is a complex, ongoing challenge that requires a multifaceted approach. The keys to success are consistency and vigilance, from sourcing clean plant materials to avoiding contamination with cultural practices and routine maintenance. When off-types appear, timely and targeted management strategies can help preserve turf quality and playability. If the situation demands it, regrassing offers a path forward that can improve playability and presentation, but this is an expensive route to take and many courses have seen off-types return after regrassing. Preventing or minimizing off-type issues should be the goal, with regrassing as an option of last resort.

References

Caetano‐Anollés, G., Callahan, L.M., & Gresshoff, P.M. (1997). The origin of bermudagrass (Cynodon) off‐types inferred by DNA amplification fingerprinting. Crop science, 37(1), 81-87.

Goatley Jr, J.M., Philley, H.W., Krans, J.V., Van Santen, E.A., Capo-chichi, L., & Davis, D. (2003). The genetic stability of six bermudagrasses as affected by chronic exposure to dinitroaniline herbicides. USGA Green Section Record, 2(10), 1-7.