Key Takeaways

• Researchers tested grasses for winter survivability, overall quality and disease resistance in cold climates. Ability to resist diseases like Microdochium patch is particularly important in Europe where limited fungicide options exist, or for superintendents anywhere wishing to reduce fungicide use.
  
  
• Among eight grass species tested in Norway, Iceland, Denmark and the U.S., creeping bentgrass was ranked highest for overall quality. The top-performing cultivars were ‘Match Play’, ‘L-93 XD’ and ‘777’. There were significant differences in winter damage and disease among the 17 cultivars tested.
  
  
• Velvet bentgrass ranked second best in overall quality. Both creeping bentgrass and velvet bentgrass were significantly better than slender creeping red fescue, Kentucky bluegrass and Chewings fescue, which all performed equally. Rough bluegrass and perennial ryegrass were ranked lowest overall.
  
  
• Among five different seed mixtures tested, the creeping bentgrass variety ‘Pure Distinction’ blended with three varieties of fine fescue performed best. Management strategy (nitrogen rate and mowing height) significantly impacts which grass becomes dominant in creeping bentgrass blends with other species. 
   

Putting greens in the Nordic countries are commonly seeded with creeping bentgrass or mixtures of colonial bentgrass and red fescue. The fescue is typically a mixture of the two subspecies, Chewings and slender creeping red fescue. Annual bluegrass is managed as a weed species on putting greens in Nordic countries, and it is rather abundant in northern areas as it will fill voids following winter damage. The use of velvet bentgrass is restricted to some golf courses in Finland, while rough bluegrass and perennial ryegrass are typically only used as nurse grasses to reestablish greens after winter damage in places with very hard winter conditions. In extremely cold Nordic climates, severe winter damage often occurs, and it is common for courses to have to establish new grass in spring. To avoid too much Poa annua infestation (from the natural seed bank), some courses seed quickly establishing rough bluegrass or perennial ryegrass in early spring just to have some green grass before bentgrass and fescue recover and start to grow again.

2019-2022 SCANGREEN Putting Green Trials

Grasses Evaluated and Locations

The SCANGREEN test round from 2019 to 2022 included eight different species and subspecies, with most entries being varieties of creeping bentgrass, Chewings fescue and slender creeping red fescue (Table 1).
 

The trials were established on putting greens built according to USGA recommendations at four Nordic locations: Reykjavik Golf Club, Iceland; NIBIO Apelsvoll and NIBIO Landvik research centers in Norway; and at Smørum Golf Club in Denmark. The annual mean temperatures at these four sites ranged from 40 to 49 degrees F and the annual precipitation ranged from 26 to 56 inches. 

The two U.S. trials were established on a green built according to USGA recommendations located at Troll Turfgrass Research Facility at the University of Massachusetts, and on a native soil push-up green at the University of Minnesota. The average annual temperature and precipitation was 59 F and 46 inches in Massachusetts and 47 F and 32 inches in Minnesota, respectively. 

Putting Green Establishment and Management

The trials were established according to a split-plot design with three replicates; grass species were on main plots and varieties on subplots. The experimental greens were mown three times per week and deficit-irrigated to 80% of field capacity three to four times per week in periods without sufficient natural rainfall. Each experimental green was divided into two different management levels (high or low mowing height and high or low nitrogen rate) based on the species potential use. All three bentgrasses (colonial, velvet and creeping) were mown at 0.120 inch, with velvet and colonial bentgrass receiving 89 pounds of nitrogen per acre per year while creeping bentgrass received 152 pounds annually. At the 0.200-inch mowing height, red fescue received 89 pounds of nitrogen per acre per year while perennial ryegrass, Kentucky bluegrass and rough bluegrass each received 152 pounds annually. 

In addition to the species and cultivars listed above in Table 1, five seed blends containing various mixtures of three red fescue varieties, two bentgrass species, and one perennial ryegrass variety were also tested and are listed in Table 2 in the results section. Those blends and mixtures were established from seed at the University of Minnesota, NIBIO Landvik research center in Norway, and Smørum Golf Club in Denmark, and were managed at both mowing and nitrogen regimes. There were some deviations from the maintenance protocol, especially during establishment and recovery after winter damage. 

No notable differences were observed among nitrogen rate or mowing height treatments for the individual species and varieties listed in Table 1 and results are not discussed. However, another focus area of this research was to better understand how nitrogen fertilizer rate and mowing height impact which species in a seed blend becomes dominant. The results of testing the five different seed blends and mixtures in Table 2 are discussed in the results section.

Treatment Applications and Data Collection 

Traffic was simulated across all plots and treatments using friction wear drums with golf spikes corresponding to an average of 11,000 rounds of golf per year. There was no use of pesticides or plant growth regulators in any of the trials. Further details on establishment and management can be found in the full report (Hesselsøe et al., 2023). 

Monthly assessments of turfgrass quality, tiller density, color, leaf fineness, and coverage of weeds and diseases were done from April or May to October or November depending on the site. Overall winter damage was recorded in spring and occurrence of diseases like Microdochium patch, gray snow mold (Typhula incarnata) and speckled snow mold (Typhula ishikariensis) were rated in autumn, early winter and spring.
 

Results: Comparing Different Grass Species and Varieties

Across the Nordic countries, creeping bentgrass followed by velvet bentgrass gave the best overall quality. Both were significantly better than slender creeping red fescue, Kentucky bluegrass and Chewings fescue, which all performed equally. Perennial ryegrass and rough bluegrass had the lowest overall quality across all trial sites.

Varieties of Chewings and Slender Creeping Red Fescue 

The varieties of Chewings fescue performed better than the varieties of slender creeping red fescue. The difference could be explained by more Microdochium patch during winter and more dollar spot (Clarireedia spp.) during summer in slender creeping red fescue. At Smørum Golf Club in Denmark, big differences between the varieties of slender creeping red fescue were observed with 20%-30% Microdochium patch during winter in several varieties compared to only 0.2% in ‘Sea Mist’ and 3.0% in ‘Cezanne’. ‘Sea Mist’ also had the lowest infection of dollar spot at Smørum, significantly lower than in several of the other varieties. ‘Sea Mist’ also had the lowest infection of dollar spot in Massachusetts, although not significantly different from the other varieties. Overall in the U.S., the variety ‘Sea Mist’ performed the best of slender creeping red fescues across the two sites.

Varieties of Colonial Bentgrass 

Across the four Nordic sites there was no difference between the colonial bentgrass varieties in overall turfgrass quality, but ‘Jorvik’ had the lowest overall winter damage and the least Microdochium patch across all years.

Varieties of Creeping Bentgrass 

In total, 17 varieties of creeping bentgrass were tested. Across the Nordic test sites ‘Match Play’, ‘L-93 XD’ and ‘777’ performed best, closely followed by ‘Piranha’, ‘Valderrama’ and ‘Luminary’. Lowest ranked in the Nordic test zones were ‘Penncross’, which had significant disease, low tiller density and coarse leaves, and ‘Pure Select’, which had more overall winter damage and infection of Microdochium patch than the other varieties of creeping bentgrass. In contrast, ‘Pure Select’ was ranked as third best in Massachusetts, but it was not tested in Minnesota. 

Results for the creeping bentgrass varieties tested at both trial sites in the U.S. show that ‘Match Play’, ‘Riptide’ and ‘L-93 XD’ were the three highest rated for overall turf quality, while ‘Penncross’, ‘Independence’ and ‘Valderrama’ were rated lowest. ‘Luminary’, ‘Tour Pro’, ‘Match Play’ and ‘Piranha’ had significantly less Microdochium patch than the other varieties, while ‘Penncross’, ‘Independence’ and ‘Valderrama’ had the most Microdochium patch across all observations. Dollar spot severity was also measured at the two U.S. sites, with ‘Piranha’ having the least amount of in-season disease while ‘Independence’ had the most.
 

Varieties of Velvet Bentgrass and Kentucky Bluegrass

‘Villa’ remained the top variety of velvet bentgrass for the Nordic countries in this round of testing, as it was in earlier trials. ‘Villa’ also had slightly higher turfgrass quality than ‘Legendary’ and ‘Avalon’ in Minnesota, while ‘Villa’ and ‘Avalon’ were equal in Massachusetts.

In Kentucky bluegrass, ‘Limousine’ produced higher turfgrass quality, higher tiller density, finer leaves and less in-season disease than the very dark-colored variety ‘Professor’. Compared to ‘Professor’, ‘Limousine’ was also more winter hardy and less infested with moss and Poa annua. Mostly because of finer leaves, ‘Traction’ was ranked higher than ‘Limousine’ at Landvik and in Minnesota. 

Results: Comparing Different Seed Blends and Mixtures

Winter Damage and Disease Performance

The first column in Table 2 below lists the treatment codes for each of the five seed blends and mixtures tested. At the high-fertilizer/low-mow maintenance treatment, the mixture of fescue and creeping bentgrass (FR+AS) had the highest overall turfgrass quality in the Nordic trials, while the mixture of fescue and colonial bentgrass (FR+AC) was ranked the lowest. Comparing overall winter damage and Microdochium patch during winter, FR+AS was also significantly better than FR+AC. In contrast, the infection of Microdochium patch across years was higher with FR+AS than with FR+AC in Minnesota, but the three mixtures with fescue and bentgrass were nonetheless very close in overall turfgrass quality in the U.S. trial. The mixture of creeping bentgrass and perennial ryegrass (AS+LP) was ranked the lowest in Minnesota with a high infection of Microdochium patch and coarse leaves.

How Does Mowing Height and Nitrogen Rate Affect Species Dominance in a Blend?

The proportion of red fescue to bentgrass in the mixed plots was investigated by counting tillers in 2020 and 2021. The proportion between red fescue and bentgrass was in favor of the bentgrasses at high-fertilizer/low-mow maintenance. The highest proportion of bentgrass was found with FR+AS followed by FR+AC+AS and FR+AC. At low-fertilizer/high-mow maintenance, the proportion between fescue and bentgrass was more balanced, though the FR+AC+AS mixture was in favor of the bentgrasses. In 2021 the dominance of creeping bentgrass was clear at high-fertilizer/low-mow maintenance as red fescue was almost entirely outcompeted on plots seeded with the FR+AS mixture. In cases where red fescue is desired to be the dominant grass for aesthetic or traditional reasons, a higher mowing height and lower fertilizer rate will give it a competitive advantage over creeping and/or colonial bentgrass. 

Implications for Practitioners

Individual Grass Species and Varieties

Among all grass species tested, creeping bentgrass was found to have the best overall quality under these specific conditions. The cultivars ‘Match Play’, ‘L-93 XD’, and ‘777’ are good options for the Nordic countries and northern parts of the U.S. Older cultivars like ‘Penncross’ are not good options for locations where disease is a primary concern. Keep in mind that golf course superintendents in the U.S. have access to many fungicides that greenkeepers in Nordic countries do not. Therefore, superintendents in the U.S. may want to weigh factors such as turf quality and winter survivability more than disease resistance. Cultivars can also perform differently based on location, as illustrated with ‘Pure Select’, which did poorly in Norway but performed well in Massachusetts. 

Although creeping bentgrass is commonly used in cold climates in the U.S., the results from this study and ongoing work show the potential for other grasses like velvet bentgrass and the fine fescues as options for golf courses in cold climates. In the right setting, Chewings fescue could be a good option for courses prone to Microdochium patch and dollar spot, specifically the variety ‘Sea Mist’. The findings regarding velvet bentgrass support previous research in the U.S. that shows when the right growing environment and golfer expectations are present, velvet bentgrass can provide a dense, fine and uniform putting surface that requires few inputs and tolerates diseases well (Brilman, 2003; Boesch & Mitkowski, 2007). The lack of velvet bentgrass seed and sod production currently limits widespread use of this grass in the U.S. The fine fescues and velvet bentgrass fit a very specific niche in the U.S. and require a unique maintenance program, nevertheless, they do offer benefits over other grasses when low inputs are desired.

Perennial ryegrass germinates quickly and can tolerate a wide range of mowing heights, but overall, it performed poorly at all sites except at Smørum. Rough bluegrass had the lowest turfgrass quality at all sites and is not a good grass choice for cold climates.
 

Seed Blends and Mixtures

Among the seed mixtures, a few clear differences were found. Fine fescue and creeping bentgrass blends would be preferred at Landvik, Smørum and similar climates in the U.S. at the high-nitrogen/low-mow maintenance, but with the risk that the creeping bentgrass outcompetes the fescue. Varieties of creeping bentgrass with a lower tiller density than ‘Pure Distinction’ should be preferred for the mixture with fescue. Although the results of this research show that creeping bentgrass performs well in cold regions, golf courses in northern Europe sometimes desire to maintain it as a subordinate or supplemental grass to a red fescue blend for aesthetic, playability, and in some cases, reasons having to do with tradition. The mixture with creeping bentgrass and perennial ryegrass established significantly faster than any of the others, but following winter, turfgrass quality decreased significantly compared to the other mixtures due to Microdochium patch, so the blend with ‘Clementine’ perennial ryegrass cannot be recommended for cold climates. 

Reducing Pesticide Use

A key objective of the SCANGREEN program is providing superintendents in Europe, who have limited pesticide options, with the best grass choices for use on courses that use little or no chemical inputs. For example, our results suggest that for courses with mixtures containing colonial bentgrass, replacing it with creeping bentgrass can reduce fungicide requirements. Again, golf course superintendents have many factors to weigh when it comes to grass choices, but if reducing fungicide inputs is a priority, selecting grass species and varieties with good disease tolerance is essential. 

Final Thoughts

The information from this study can guide superintendents in selecting grasses that will perform well in cold climates, but as with any turfgrass conversion, testing potential grass options on a small scall in the unique environment and maintenance program of a particular golf course is essential for making the best choices. 

The next round of trials by SCANGREEN has been funded by STERF for 2023-2026 and are currently underway. The U.S. trials are continuing in Minnesota and are now funded by the WinterTurf project.
 

References

Boesch, B.P., & Mitkowski, N.A. (2007). Management of velvet bentgrass putting greens. Applied Turfgrass Science, 4, 1-6. https://doi.org/10.1094/ATS-2007-0125-01-RS

Brilman, L.A. (2003). Velvet bentgrass (Agrostis canina L.) In: M.D. Casler & R.R. Duncan (Eds.), Turfgrass biology, genetics, and breeding. John Wiley & Sons.

Hesselsøe, K.J., Borchert, A.F., Aamlid, T.S., Hannesson, B., Rasmussen, P., Normann, K., Espevig, T., DaCosta, M., Watkins, E., Hollman, A., Hornslien, J., Petterson, T., & Heltoft, P. (2023). SCANGREEN 2019-2022: Turfgrass species, varieties and seed mixtures for Scandinavian putting greens. Final results from a four-year testing period. NIBIO Rapport.