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Cultivar selection could influence interseeding success

October 27, 2009

Germination characteristics such as speed, synchrony, and viability determine the success of newly seeded areas. Traditional establishment from seed involves sowing seed into bare soil or turf which have been treated with non-selective herbicides. In either case, the newly emerging seedlings face little competition from surrounding plants. While germination characteristics are important when using traditional establishment methods, superior germination characteristics may be necessary when using non-traditional seeding methods such as interseeding.

Interseeding poses an interesting dilemma. The main attraction of converting through interseeding is the ability to convert to a new turf without taking the area out of play and facing the resulting economic losses. Research shows that the success of interseeding is related to the level of disruption created and the speed of germination of the interseeded species. As the level of disruption increases, the competition from surrounding plants decreases allowing the seedlings an opportunity to establish. However, the amount of disruption necessary for successful interseeding may not be conducive with a smooth uniform playing surface. Because minimal disruption is needed so as not to disrupt play, superior germination characteristics are needed.

We conducted a germination study at Iowa State with 'Penncross' and 14 improved cultivars of creeping bentgrass. The cultivars ‘L-93’, ‘T-1’, ‘Apha’, ‘Penn A-1’, ‘Penn A-4’, ‘Crystal Bluelinks’, ‘Pennlinks II’, ‘Pencross’, ‘Tyee’, ‘007’, ‘Mackenzie’, ‘SR1150’, ‘Memorial’, ‘Independence’, and ‘Declaration’ were evaluated in this study. Each cultivar was represented by two to four seeds lots from production year 2007. Standard germination tests were conducted according to the rules established by the Association of Official Seed Analysts (AOSA). The objectives of the study where to determine if improved cultivars of creeping bentgrass possess superior germination characteristics compared to 'Penncross' and if there was a relationship between seed weight and germination characteristics.


Significant differences existed between 'Penncross' and the improved bentgrass varieties for germination speed (MGT), germination synchrony (T10-90), and viability (FGP) but not weight (table 1). These results indicate that improved varieties of creeping bentgrass possess greater viability and germinate faster and with greater synchrony compared to ‘Penncross’. Differences between ‘Penncross’ and each of the improved varieties can be viewed in table 2 (significant differences are highlighted in red). ‘T-1’ outperformed ‘Penncross’ in all three parameters. While some of these differences appear small numerically, it is important to remember that these tests were conducted under optimum conditions. The differences would likely be greater under field conditions when the seeds are subject to environmental stresses.

Our study also revealed a significant correlation between seed weight and speed of germination (MGT). Seeds germinated faster as the weight of the seeds increased. This information could be used to predict the germination speed of other cultivars without conducting tedious germination studies.

What does it all mean?

This study clearly shows that improved cultivars of creeping bentgrass have superior germination characteristics compared to ‘Penncross’. So is it possible that the success or failure of interseeding could depend on cultivar selection? Past interseeding research supports this very idea. Attempts at interseeding ‘Penncross’ into an established annual bluegrass putting green were largely unsuccessful (Gaussoin et al., 1989). However, in a similar study, researchers were able to establish over 70% ‘L-93’, and ‘Penn A-4’ into an annual bluegrass putting green (Henry et al., 2005). These results could be the explained by the differences in germination characteristics that we observed in our study. Clearly, not all cultivars of creeping bentgrass exhibit similar germination characteristics. And while the success of interseeding will not result from a single practice or strategy, proper cultivar selection will play an integral role as part of an interseeding conversion program.

Literature Cited

Gaussoin, R.E. and B.E. Branham. 1989. Influence of cultural factors on species dominance in a mixed stand of annual bluegrass/creeping bentgrass. Crop Sci. 29:480-484.

Henry, G.M., S.E. Hart, and J.A. Murphy. 2005. Overseeding bentgrass species into existing stands of annual bluegrass. HortScience 40:468-470.

Marcus Jones
Graduate Research Assistant


Interseeding Study at Hyperion Field Club

July 27, 2009

The research for my PhD program focuses on interseeding. Specifically, I am interested in developing methods which would allow a turf manager to convert to new, improved varieties without taking an area out of play. Interseeding is such an interesting topic because it has been an area of great debate. Most researchers contend interseeding is not possible while some turf managers insist interseeding is an effective way to add turf to already established areas.

One of my interseeding studies is located on a practice putting green at Hyperion Field Club. Below are the details of the study and why I think this project has a chance to be successful.

Presence of Poa annua – The practice green where the study is located has between 50-60% poa. So why would this help the interseeding process? The success of establishing new seedlings in existing turf is closely tied to plant competition. Trying to establish a cool-season species in established cool-season turf is difficult because they both share the same growth cycle. This is also the reason why overseeding in the southern U.S. is so successful. Cool-season grasses seeded into warm-season turf works quite well because they have different growth cycles. In our situation, even though poa is a cool-season species it is a winter annual. Winter annuals germinate in the fall persist through the winter and spring before ending their lifecycle during the summer months.

Products that harm Poa annua – There are perennial-type poa’s as well, but they are generally more susceptible to summer stresses compared to creeping bentgrass. Our study is utilizing Velocity and Trimmitt, both products that harm poa more than bentgrass. Velocity applications started June 4 and were applied at 2 oz/A every 14 days for a total of 4 applications. Trimmitt applications also started June 4 and are being applied at 6 oz/A every 14 days. A total of 8 applications of Trimmitt will be made.

Establishing a creeping bentgrass seedbank – There are many plants that have been classified as “invasive” species. A shared trait of these plants is their ability to produce large volumes of seed and establish a seed bank. This is one reason why poa is so successful at colonizing established putting greens. I am borrowing this concept and attempting to establish a seedbank of creeping bentgrass. Bentgrass seed is being spiked into the green every 14 days at a rate of 1.5 lbs/1000 f

Accurate, non-disruptive spiker/seeder – The attraction of converting through interseeding is that play can continue during the conversion and revenue is not lost. Therefore, the process of placing the seed into the putting green must be non-disruptive. I’m using a walk-behind Maredo spiker/seeder to seed into the putting green. The company that manufactures this machine also makes floating heads that mount on a triplex unit. This machine accurately meters creeping bentgrass seed into many small holes. There is minimal disruption and play can follow directly behind the machine.

Choosing aggressive varieties of bentgrass – Because the Maredo creates minimal disruption, the opportunity for new seedlings to germinate and establish before the holes close is small. Therefore, it is crucial that the bentgrass species selected for the interseeding process possess high vigor. I recently conducted a germination experiment with many of the new, improved bentgrass cultivars. The results of this study showed that the cultivars T1, Penn A-1, Penn A-4, Crystal Bluelinks, Pennlinks II, Independence and Declaration germinated significantly faster compared to Penncross. Based upon these results, I am using Penn A-4 as an interseeding species.

Interseeding timing and seeding rate – In addition to spiking seed every two weeks to half of each plot, the entire study is interseeded three times a year: May 28, July, 30, and September 17. The May 28 and September 17 calendar dates correspond with spring and fall aerification and seed is sown at 1.5 lbs/1000 ft2. Research has shown that interseeding into poa is most effective when performed mid-summer. The July 30 calendar date is designed to introduce seed into the putting surface when poa is at a competitive disadvantage due to summer stresses in addition to the Velocity or Trimmitt. The July 30 seeding will be sown at 3.0 lbs/1000 ft2. The higher than normal seeding rates are designed to account for the high mortality rates expected from traffic and plant competition.

I started the study this spring and it’s scheduled to run for two years. My first round of data will be collected this fall and I will be presenting the results at the Iowa Turfgrass Conference. Any comments or questions regarding this work can be directed to

Marcus Jones
Graduate Research Assistant