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Key Takeaways

  • ‘Lazer’ zoysiagrass was significantly more shade tolerant than ‘TifEagle’ bermudagrass and maintained acceptable quality down to a daily light integral (DLI) of 15.6 moles of light per square meter per day while ‘TifEagle’ required a DLI of 31.4 moles.

  • The plant growth regulator (PGR) trinexapac-ethyl improved the shade tolerance for ‘TifEagle’ but did not benefit ‘Lazer’. With trinexapac-ethyl treatments, ‘TifEagle’ retained acceptable quality down to a DLI of 24.6 moles.

  • Raising the height of cut from 0.100 inch to 0.125 inch improved turf quality in shade for both species but had a greater effect on ‘TifEagle’.

  • ‘TifEagle’ had consistently higher green speeds than ‘Lazer’, but the speed measurements were typically within 1 foot of each other after the establishment year.

  • ‘Lazer’ produced a firmer surface than ‘TifEagle’, but firmness values for both grasses remained in an acceptable range for playability throughout the study.
     

Shade is a serious challenge for many golf courses, especially when it affects putting greens. Reduced light directly impacts photosynthesis and can ultimately lead to lower turf quality, reduced density, slower recovery and inconsistent playability.

In warm-season climates, golf course superintendents commonly use ultradwarf bermudagrass cultivars like ‘TifEagle’ for putting greens. While bermudagrass performs well under full sunlight, it often struggles to produce high-quality surfaces for both daily play and championship situations when shade is an issue. Zoysiagrass (Zoysia spp. Willd.) is emerging as an alternative to both hybrid bermudagrass (Cynodon dactylon (L.) Pers. x Cynodon transvaalensis Burtt-Davy) and creeping bentgrass (Agrostis stolonifera L.) putting greens in the transition zone because it can tolerate hot and humid conditions better than cool-season grasses and certain varieties can tolerate shade and cold temperatures better than many bermudagrass varieties. Zoysiagrass putting greens are commonly found in East and Southeast Asia where it is indigenous, but it is rarely used on putting greens in the United States. Its use in Asia is primarily because bermudagrass does not thrive under the cloudy conditions in the region, while the tropical temperatures are too warm for cool-season grasses like creeping bentgrass (Woods, 2014).

Developing Zoysiagrasses for Putting Greens

‘Diamond’ zoysiagrass (Zoysia matrella (L.) Merrill) was released in 1996 as the first commercially available zoysiagrass for putting green use in the United States (Engelke et al., 2002). ‘Diamond’ has a very fine leaf texture, high tiller and rhizome density, and has also been shown to exhibit excellent shade tolerance (Atkinson et al., 2012; Qian & Engelke, 2000). However, many practical concerns made ‘Diamond’ putting greens less favorable than bermudagrass, including slow establishment from sprigs, stiff and rigid leaf blades, and prolific seedhead production (Briscoe et al., 2012; McCullough et al., 2017; Stiglbauer et al., 2009).

The variety ‘Lazer’ is a putting green zoysiagrass developed at Texas A&M and is a hybrid between Zoysia matrella (L.) Merrill and Zoysia minima (Colenso) Zotov (Chandra et al., 2020). Known originally by its experimental name ‘DALZ 1308’, it was a top performer in the 2013 National Turfgrass Evaluation Program (NTEP) warm-season putting green trial and was commercialized by Bladerunner Farms in Poteet, Texas, in 2019 as ‘Lazer’ zoysiagrass (NTEP, 2017). The development of new genetic lines of zoysiagrass could be a significant advancement for golf course managers in the transition zone. Still, field research is needed to determine environmental limits, appropriate cultural practices and the inputs required to produce putting surfaces that can compete with current industry standards such as bermudagrass or creeping bentgrass.

Light Requirements of Zoysiagrass and Bermudagrass

Plants primarily utilize light in the photosynthetically active radiation (PAR) spectrum, which encompasses wavelengths of light between 400-700 nanometers (nm). The daily light integral (DLI), expressed in moles of light per square meter per day (mol m⁻² d⁻¹), represents the cumulative amount of PAR a surface receives over a 24-hour period and has been used to establish the minimal light requirements for various turfgrasses (Bunnell et al., 2005; Chen et al., 2021; Chhetri et al., 2019; Richardson et al., 2019; Russell et al., 2019). In this article, the units for all DLI values listed are in moles of light per square meter per day. For turfgrass, knowing the minimum DLI and maintaining light levels above that threshold is essential to support healthy growth. Previous work has shown that ‘TifEagle’ bermudagrass requires a minimum DLI of 30 to 33 to sustain acceptable turf quality at putting green mowing heights (Bunnell et al., 2005). In contrast, the zoysiagrass cultivar ‘Diamond’ was able to maintain performance at a minimum DLI of approximately 18 (Atkinson et al., 2012).  

Research Study: Shade, Height of Cut and PGR Effects on Bermudagrass and Zoysiagrass Putting Greens

The overall goal of this work was to evaluate the performance of ‘Lazer’ zoysiagrass compared to ‘TifEagle’ bermudagrass under varying light conditions, from full sun to 80% shade. In addition, two other factors commonly known to affect shade performance of grasses – height of cut and PGRs – were also studied in the trial. The primary objective of this field trial was to determine the minimum light required (reported as DLI) to maintain acceptable quality of ‘TifEagle’ bermudagrass and ‘Lazer’ zoysiagrass putting greens. A second objective was to monitor the surface characteristics of each species, including green speed and surface firmness, to determine if ‘Lazer’ zoysiagrass performs comparably to an industry-standard ultradwarf bermudagrass. The full results from this study can be viewed in a recent journal article (Walton et al., 2024).

Experimental Methods

The study was conducted at the Milo J. Shult Agricultural Research and Extension Center in Fayetteville, Arkansas. Experimental plots of ‘TifEagle’ and ‘Lazer’ were established in 2019 on a sand-based putting green built according to USGA recommendations for putting green construction. Treatments applied during the 2020 and 2021 growing seasons included five levels of shade (0%, 20%, 40%, 60% and 80%), two mowing heights (0.110 and 0.125 inch), and weekly applications of trinexapac-ethyl (TE) as well as a no-PGR treatment.

Shade structures were custom-built with neutral-density cloth and mounted on wheeled frames to simulate realistic season-long shading. Light levels were measured using LightScout Quantum PAR sensors (Spectrum Technologies), and DLI was calculated using integrated photosynthetic photon flux (PPF) values recorded every 30 minutes. The turf was maintained with typical management practices for putting greens in the transition zone, including mowing six times per week, biweekly topdressing, routine irrigation and regular fungicide applications.

Evaluations in this trial included visual turfgrass quality, green speed and surface firmness. Visual turfgrass quality ratings based on uniformity, density, coverage and color of the turfgrass were recorded weekly and the authors established a rating of “7” as the minimally acceptable turfgrass quality score for this trial. Green speed and surface firmness were assessed every two weeks. A Stimpmeter was used to measure green speed following the methods defined by the USGA. A Clegg Impact Tester (Turf-Tec International) equipped with a 5-pound hammer was used to evaluate surface firmness. The impact of the hammer produces an electrical pulse, which is converted and displayed in gravities called the Gmax. The higher the value, the firmer the surface. For reference, a Gmax value of 77 corresponds to a firmness of 0.450 measured with the USGA’s GS3 Ball, which would be a typical value for a putting green of “average” firmness. Surface firmness was recorded as the average of three separate hammer drops per plot and reported as the average Gmax value of the three drops.

Results and Discussion

‘Lazer’ was slower to establish than ‘TifEagle’, which impacted turf quality ratings in early 2020. However, once established, it demonstrated good tolerance to 40% and 60% shade, maintaining quality scores above the industry-accepted minimum of 7 on a 1 to 9 scale. In contrast, ‘TifEagle’ quality rapidly declined under similar shade levels. Raising the height of cut to 0.125 inch improved quality for both grasses, but the impact was more pronounced for ‘TifEagle’.

One of the major outcomes of the study was determining the minimum DLI required to maintain acceptable turf quality for each variety (Figure 1). For ‘TifEagle’ bermudagrass, the average minimum DLI requirement across two seasons was 31.4 moles without TE and 24.6 moles with TE – similar to earlier results by Bunnell et al. (2005). ‘Lazer’ maintained acceptable turf quality with a DLI as little as 15.6 moles and its light requirements were largely unaffected by mowing height or TE. This significant difference highlights the superior shade tolerance of zoysiagrass. Comparisons with previous studies on ‘Diamond’ and other zoysiagrass cultivars suggest that ‘Lazer’ sets a new benchmark for greens-type zoysiagrasses in low-light environments.

Green speed remains an important measure of playability and ‘TifEagle’ had higher green speed measurements than ‘Lazer’ on almost all dates in both 2020 and 2021 (Figure 2). It is worth noting that green speeds more than 11.0 feet were routinely observed on ‘Lazer’, which supports research by others showing that “championship” green speeds can be obtained with new zoysiagrass cultivars. In a recent study, green speeds above 14.0 feet were observed with ‘Lazer’ and an experimental zoysiagrass cultivar called ‘M85’ (Carr et al., 2022). Over the course of each season, green speed increased for both grasses and were comparable at the end of the summer.

Surface firmness was consistently higher (firmer) for ‘Lazer’, with Gmax values 11% to 21% firmer than ‘TifEagle’ (Figure 3). While this contributes to smoother putting conditions by increasing resistance to traffic, it may affect the ability to hold golf shots into the green. However, all firmness values fell within ranges similar to those found on golf courses during daily play or championship scenarios. Differences in water retention and organic matter accumulation could help explain these results and warrant additional investigation. Zoysiagrass is also known for its stiff and dense turf canopy compared to bermudagrass, so it is plausible that “canopy architecture” and/or leaf stiffness play a role as well.

Implications for Golf Course Superintendents

Superintendents dealing with shaded green sites should consider ‘Lazer’ as a viable alternative to bermudagrass and creeping bentgrass, which has a similar DLI requirement as ‘TifEagle’ (Russell et al., 2019). It offers superior performance under low light and produces firmer surfaces than bermudagrass with slightly slower, yet comparable, green speeds. This grass also performs well in full-sun settings. However, as is the case with most zoysiagrasses used in the golf industry, it is slower to establish from sprigs than bermudagrass and may require sod installation or an extended grow-in schedule. Although this research demonstrates the benefits of zoysiagrass for shaded putting greens, there are additional issues and concerns related to zoysiagrass greens superintendents need to weigh and that researchers continue to work on. Controlling spring seedheads can be challenging and there is still more to learn about the relative cold tolerance of zoysiagrass greens. Long-term management will also be different as zoysiagrass produces significant thatch and organic matter and is very slow to recover from disruptive maintenance (e.g., core aeration) compared to bermudagrass.

To understand whether the greens on a golf course would potentially perform better with zoysiagrass from a shade tolerance perspective, superintendents should use a quantum PAR sensor to objectively determine the DLI at each green site (Richardson & Kruse, 2015). Sites receiving less than 20 moles of light per square meter per day are likely poor candidates for ‘TifEagle’ or creeping bentgrass. Raising the mowing height and using TE on bermudagrass may help extend its viability under moderate shade but an improved zoysiagrass will likely perform better in the long run.

This research illustrates that ‘Lazer’ zoysiagrass is well suited for shaded putting greens and outperforms ‘TifEagle’ bermudagrass under low-light conditions. While ‘TifEagle’ remains the gold standard for speed and playability under full sun, ‘Lazer’ fills a much-needed role for superintendents struggling with shade-affected greens. Under the right management, ‘Lazer’ can offer comparable or superior surface firmness, traffic tolerance and resistance to Poa annua invasion that make it a potentially appealing option beyond shaded settings. Zoysigrass putting greens remain an uncommon sight, but courses with heavily shaded greens report that making the switch from either ultradwarf bermudagrass or creeping bentgrass to zoysiagrass greens has been beneficial. Ongoing studies funded by the USGA are exploring issues such as herbicide tolerance, seedhead suppression and growth regulation strategies for this and other promising new zoysiagrass cultivars.

References

Atkinson, J.L., McCarty, L.B., Liu, H., Faust, J., & Toler, J.E. (2012). Diamond zoysiagrass golf green response to reduced light environments with the use of trinexapac-ethyl. Agronomy Journal, 104(4), 847-852.

Briscoe, K., Miller, G., Brinton, S., Bowman, D., & Peacock, C. (2012). Evaluation of ‘Miniverde’ bermudagrass and ‘Diamond’ zoysiagrass putting green establishment using granular fertilizer applications. HortScience, 47(7), 943-947.

Bunnell, B.T., McCarty, L.B., Faust J.E., Bridges, W.C., Rajapakse, N.C., & Bridges, W.C. (2005). Quantifying a daily light integral requirement of a TifEagle bermudagrass golf green. Crop Science, 45(2), 569-574.

Carr, T.Q., Sorochan, J.C. & Dickson, K.H. (2022). Nitrogen rate and cultivar effects on zoysiagrass putting greens in the transition zone. Crop Science, 62(6), 2476-2485.

Chandra, A., Genovesi, A.D., Meeks, M., Wu, Y., Engelke, M.C., Kenworthy, K., & Schwartz, B. (2020). Registration of ‘DALZ 1308’ zoysiagrass. Journal of Plant Registration, 14(1), 19-34.

Chen, Z., Wherley, B., Reynolds, C., Hejl, R., & Chang, B. (2021). Daily light integral requirements for bermudagrass and zoysiagrass cultivars: Effects of season and trinexapac-ethyl. Crop Science, 61, 2837-2847.

Chhetri, M., Fontanier, C., Koh, K., Wu, Y., & Moss, J.Q. (2019). Turf performance of seeded and clonal bermudagrasses under varying light environments. Urban Forestry & Urban Greening, 43, 1-8.

Engelke, M.C., Colbaugh, P.F., Reinert, J.A., Marcum, K.B., White, R.H., Ruemmele, B., & Anderson, S.J. (2002). Registration of ‘Diamond’ zoysiagrass. Crop Science, 42, 304-305.

McCullough, P.E., Yu, J., & Williams, S.M. (2017). Seedhead development of three warm-season turfgrasses as influenced by growing degree days, photoperiod, and maintenance regimens. International Turfgrass Society, 13(1), 321-329.

Qian, Y.L., & Engelke, M.C. (2000). ‘Diamond’ zoysiagrass as affected by light intensity. Journal of Turfgrass Management, 3(2), 1-13.

Richardson, M.D., Mattina, G., Sarno, M., McCalla, J.H., & Karcher, D.E. (2019). Shade effects on overseeded bermudagrass athletic fields: I. Turfgrass coverage and growth rate. Crop Science, 59(6), 2845-2855.

Richardson, M.D. & Kruse, J. (2015). Daily light integration – a new way to document shade issues. Golfdom, 71(5), 36-39.

Russell, T.W., Karcher, D.E., & Richardson, M.D. (2019). Daily light integral requirement of a creeping bentgrass putting green as affected by shade, trinexepac-ethyl, and a plant colorant. Crop Science, 59(4), 1768–1778.

Stiglbauer, J.B., Liu, H., McCarty, L.B., Park, D.M., Toler, J.E., & Kirk, K. (2009). ‘Diamond’ zoysiagrass putting green establishment affected by sprigging rates, nitrogen sources, and rates in the southern transition zone. HortScience, 44(6), 1757-1761.

Walton, T.E., McCalla, J.H., Karcher, D.E., Hutchens, W.J., Chandra, A., & Richardson, M.D. (2024). Shade, height of cut, and plant growth regulator effects on bermudagrass and zoysiagrass putting greens. Crop Science, 65(1) 1-16.

Woods, M. (2014). Zoysia on putting greens? Why? Asian Turfgrass Center. Bangkok, Thailand. https://www.asianturfgrass.com/post/zoysia-on-putting-greens-why/