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PENNSYLVANIA TURFGRASS: David R. Huff, Ph.D., Professor, Penn State University

Even in the current era of elaborate conspiracy theories and stories of bird-like aliens, and others having secret military bases on the dark side of the moon, it’s hard to imagine anything as contentious as Poa annua in today’s golf industry. For example, contrary to a recent survey that claims Poa annua is the golf industry’s third-most popular (aka abundant) turfgrass species (Golf Course Environmental Profile, 2017), most superintendents are committed to eradicating it. Conversely, despite Poa annua being the only turfgrass species in use that lacks any improved varieties and exists solely as local land races, a majority of the best golf courses strive to propagate it (https://www.top100golfcourses.com). For the past 100 years, the controversial ‘friend vs foe’ status of Poa annua has heavily favored its eradication. However, it is now time to begin exploring the best management practices (BMPs) for its propagation. That’s because soon a commercial seed source of improved varieties that have been specifically bred for use on greens and fairways will become available (see Huff, 2022). In this article, we’ll explore the grow-in of a 2022 golf course evaluation trial of Poa annua on greens and fairways.

Testing Trials

One of the first steps that needs to be undertaken during the release of any new variety of turfgrass is its evaluation at different locations, which I initiated with experimental varieties from my Penn State Poa annua breeding program back in the early 2000’s (see for example, Mitra et al., 2009). I first trialed my experimental Poa annua varieties back in 2002 at Apawamis GC, Rye, NY (Fig. 1). Superintendent Bill Purdy had just harvested sod from three of his Poa greens to enlarge his remaining 15 Poa greens, and then used Penn State Poa seed to reseed his three bare greens. Establishment went well and his members were thrilled with the results. However, about 10 years later, we realized that the problem with Poa annua commercialization was not varietal development but rather varietal instability during seed production, and it took another seven years of research after that to solve the problem. During those intervening years, Superintendent, Michael McCormick (Apawamis superintendent from 2016-2022; currently, superintendent at Oakmont CC, PA) observed that those Penn Poa greens were more tolerant of biotic and abiotic stress and used less water than the other 15 greens of the local Poa. Now that we’ve solved the commercial seed production problem and are able to produce seed of phenotypically stable Poa annua, I’ve organized a new evaluation trial of the final commercial seed product at six trial locations which includes golf courses on the East & West Coasts and from the Northern to Southern Appalachian Mountains (Fig 2.).

This new 2022 Poa annua trial has now been established at five of the six trial locations, with the Cypress Point Club (CA) trial (delayed due to weather and events) to be established in July 2023. The following are some early observations of establishment and grow-in of Poa annua at these sites.

Seeding Rates

Early in the breeding program there was never enough seed to plant the areas we needed to establish, so we had to stretch seedings to their maximum lowest rates in order to plant the largest possible sized areas we could. As such, we’ve planted greens as low as 0.3lb/K, but those areas took an entire growing season to properly fill in. We eventually settled on a 1lb/K seeding rate which is a relatively low seeding rate for Poa, but after a fall planting, it gave us an opportunity to watch the experimental varieties complete their grow-in during the following spring and we had full stands to evaluate over their first summer. Personally, I prefer low seeding rates because it results in strong, healthy seedlings as compared to extremely high seeding rates (> or = 3lbs/K) which results in overly dense, weak seedlings that encourage diseases like damping off disease (caused by Pythium and/or Rhizoctonia) due to interplant competition, low light, and poor air circulation. For the 2022 Poa Trial, we increased the seeding rate to 1.25-1.3lb/K, however, in hindsight, I would’ve liked to have increased this rate to 1.75-2.0 lb/K, which I think is a good compromise between healthy seedlings and rapid establishment.

Planting Dates

A range of planting dates have been a natural outcome of the various trial locations, and we’ve found that the Pa-33 Poa annua variety is capable of becoming established at any dates we’ve planted throughout the year. The new Apawamis GC (NYC) trial was planted June 12, 2022, and thus grow-in took place over the warm, humid summer (Fig. 3). The Highlands CC (NC) location, however, was planted on September 25, 2022, which is very late owing to the fact that Highland, NC is one of the highest cities east of the Mississippi at 4,180’ elevation. Thus, Highland’s grow-in started with temperatures in the 30’s & 40’s F, and with the cold spring weather, has never really experienced any warm temperatures right up to the time of writing this article (Fig. 4). Despite these cold temperatures, Pa-33 has become established and the Highland’s nursey area will fill in nicely with some warm weather, added fertility, and close mowing. Laurel Creek CC (NJ), just outside of Philadelphia, also had a late season planting on November 8, 2022 (Fig. 5). However, a late fall fertilization of organics on December 8 and playing the on/off game with covers throughout the winter enable the green to fully grow in by March 13, 2023 (pictured). The remaining two locations (Wildwood CC & Penn State) both were planted on September 9, 2022 (Figs. 6 & 7). While both these sites are similar in elevation and fall/winter/spring temperatures, their difference in establishment seems to be primarily related to differences in mowing heights during the initial
period of establishment.

Mowing

One of the more interesting observations made in the 2022 trial to date involves mowing height differences during initial seedling establishment. All of the trial locations, except for Penn State, established their Poa annua under an initial mowing height of 0.30 – 0.35″ for the first several months and, by months five or six, had only reduced the height-of-cut down to 0.25″. Whereas at Penn State, we had already achieved a 0.125″ height-of-cut by 6.5 weeks after planting and had vertical mowed in two-directions by that time (Fig. 7). Even though the Penn State green was not completely filled-in by 6.5 weeks, the aggressive mowing practices seemed to encourage substantial lateral growth resulting in a puttable surface by 10 to 12 weeks after planting.

No management instructions were given to the trial superintendents prior to planting, so each was left to manage their establishment as best they saw fit. Thus, it was curious to me that such a wide range of experience and locations all managed the Poa establishment so similarly. It was only when Elliott L. Dowling, USGA Regional Director, East Region, had commented that it seemed as though all of these superintendents were managing their Poa grow-in as though it were creeping bentgrass that it dawned on me that no one has actually had the experience of growing in Poa annua directly from seed. In the future, such trials will also help us to find and identify those management practices that will most quickly and properly establish playable surfaces from newly seeded Poa annua (Fig. 8).

Summary & Conclusions

Thus, in addition to evaluating the performance of Poa annua varieties specifically bred for greens and fairways, golf course evaluation trials will also serve to identify BMPs for seedling establishment, grow-in, and eventually maintaining Poa annua playing surfaces. Currently, there is little information available for BMPs regarding propagation of Poa annua playing surfaces. One good source of such information is a brief overview by Prof. Tom Cook, Oregon State University (see Cook, 2008). The use of Poa annua on golf courses will likely always be controversial. However, with a steady seed supply of improved Poa annua we’ll be able to begin assessing the “known knowns” and the “known unknowns” regarding the maintenance of Poa annua as well as no doubt discover as many “unknown unknowns” as we are willing to admit to concerning the utility and performance of Poa annua on golf course playing surfaces.

Conflict of Interest Disclosure:

Dr. Huff has a financial interest in PennPoa LLC. This interest has been reviewed by the University in accordance with its Individual Conflict of Interest policy, for the purpose of maintaining the objectivity and the integrity of research at The Pennsylvania State University.

References

Cook, T. 2008. Annual bluegrass, Poa annua L. 7 pgs. http://www.kinipela.ca/pdf/AnnualBluegrass2008.pdf

Golf Course Environmental Profile. 2017. Land Use Characteristics and Environmental Stewardship Programs on U.S. Golf Courses. USGA & GCSAA. https://www.gcsaa.org/docs/default-source/Environment/phase-2-land-use-survey-full-report.pdf?sfvrsn=c750ea3e_2

Huff D.R. 2022. Coming soon: Poa annua seed for greens and fairways. Pennsylvania Turfgrass 11 (3):12-14. Cover Story.

Mitra, S. S., M. Seaman, M. Fam, R. Plumb, A. Malazian, D. McKee, R. Green, K. Davidson, D.R. Huff. 2009. Evaluating new Poa annua cultivars under warmer growing conditions. USGA Turfgrass and Environmental Research Online. May 15. 8(10):1-10. http://usgatero.msu.edu/v08/n10.pdf