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Interseeding Improved Cultivars of Creeping Bentgrass into Existing Putting Greens

June 20, 2011

Recently released cultivars of creeping bentgrass are available that possess more desirable agronomic characteristics. Traditional conversion involving the use of non-selective herbicides or soil fumigants is costly and time consuming. Interseeding has been proposed as an alternative conversion method. Interseeding is a method of conversion where seed is sown into an established grass sward. The goal is for the introduced cultivar or species to become the major component of the sward over time.

A variety of factors influence the success of interseeding. Gap size has been found to influence the early success of seedlings. However, significant disruption to the canopy would reduce the uniformity of the playing surface and may not be desirable to golfers.

Factors such as germination speed and seed size have also been found to influence the success of seed sown into areas with established plants. In addition, research shows that seeding at above average rates has been advantageous when trying to establish turf cover when traffic is present.

The objectives of this study were to evaluate the ability of converting an established golf course putting green via interseeding.

Materials and Methods
An interseeding study was conducted on an established practice putting green at Hyperion Field Club in Johnston, Iowa and on a research putting green in 2009 and 2010. Four replications arranged in a split block experimental design were used to evaluate three plant protectants (main plots) and two seeding regimes (subplot within main plot). Main plots treatments included a non-treated control, applications of Velocity herbicide, or Trimmit plant growth regulator. Sub plot treatments included seed sown into the canopy twice or nine times.

A Maredo seeder with vibratory spikes was used throughout the season to seed into the existing canopy at 1.5 lb/1000ft2 for seasonal totals of 4.5 or 13.5 lbs/1000ft2. Velocity was applied every 14 days at 2 oz/A starting 4 June 2010 and concluding 16 July 2010 for a total of four applications. A fifth and final application of Velocity was made 1 October 2010 at the same rate. Trimmit was applied every 14 days at 6 oz/A starting 4 June 2010 and concluding 10 September 2010 for a total of eight applications.

Regular maintenance practices were only slightly altered as the goal was to preserve conditions that would be conducive for the play of golf. Irrigation via hand-watering was conducted during the summer months in order to provide moisture to promote germination. Regular maintenance included mowing performed daily to a height of 0.125 in. and overhead irrigation was applied as necessary. Fertilizer (7N-7P-7K) was applied at a rate of 0.25 lb N/1000 ft2 each month of the growing season and diseases and insects were controlled as necessary.

Plant samples were collected during the fall of each year prior to snowfall and the following spring for evaluation of Penn A-4 populations. Cultivar identification was performed by using random amplified polymorphic DNA markers.

Results and Discussion
Five months after initial seeding, the 4.5 and 13.5 lb/1000 ft2 seeding regimes resulted in a 19 and 39 percent conversion to Penn A-4, respectively (Figure 1). However, twelve months after initial seeding, Penn A-4 populations were reduced to 1 and 8 percent for the 4.5 and 13.5 lb/1000 ft2 seeding rate, respectively (Figure 2).


Figure 1. Percentage conversion of an established putting green to Penn A-4, five months after initial seeding.  Values within seeding regimes followed by the same letter are not different at P = .05




Figure 2. Percentage conversion of an established putting green to Penn A-4, 12 months after initial seeding. Values within seeding regimes followed by the same letter are not different at P = .05

These data indicate a transient shift to Penn A-4 occurred but was not able to persist. Additionally, applications of Velocity or Trimmit did not hasten conversion to Penn A-4 (Figures 1 and 2). The lack of establishment is likely due to competition from the surrounding turf and mechanical and environmental stresses.

During the first year of the study, the percentage of annual bluegrass was reduced from approximately 60 to 20 percent in plots treated with Velocity. No loss of density occurred, but phytotoxicity was observed in plots treated with Velocity. Significant loss of density was observed during the second year of the study from Velocity applications.

Conversion was more persistent on the research putting green. The 13.5 lb/1000 ft2 seeding regime resulted in a 42% establishment of Penn A-4 the fall following interseeding (Figure 3). Evaluation of the plots the following spring revealed 45% Penn A-4 still present. Although interseeding was more successful in the research setting, the overall quality of the turf would not be acceptable for most putting greens.


Figure 3. Percentage conversion of a research putting green to Penn A-4. Values followed by the same letter are not different at P = .05

These results suggest that the level of maintenance and overall quality of the putting surface influence the success of conversion. Conversion through interseeding in this study was not successful when the plots were maintained under golf course conditions. Interseeding was only successful when conditions were allowed to deteriorate below acceptable levels. The overall conditioning of the putting surface in order to permit interseeding needs to be weighed against the cost of a traditional conversion when deciding on a renovation program.




Iowa Turfgrass Field Day Recap, Part 2

July 28, 2011

Below is the second part of the 2011 Iowa Turfgrass Field Day Recap. This article highlights talks focusing on summer seeding methods, updates on moss and algae control on putting greens, apps for turf managers and GPS spraying.

Summer seeding: During this talk, some of the ideas about seeding rates and timing were discussed to give turf managers more tools when deciding when to seed, for what purpose, and how much to seed during different times. The philosophy and science behind traditional seeding rates and higher than normal rates were discussed and a demonstration was in place to show what different seeding rates look like as well as ways to determine how much seed you are putting out without properly calibrated equipment. Lastly, we discussed how higher than normal seeding rates can reduce herbicide inputs by outcompeting weeds.

If you ever need to determine how much seed you have put out, there is a simple rule you can follow. If you are sticking to normal seeding rates (1.5 lbs/1000 ft2 for KBG; 8 lbs/1000 ft2 for PR and TF), you can always pick out a 1 square inch area and could how many seeds you see. You should count somewhere around 16 seeds in a square inch for either of the seeding rates listed above.

Higher than normal seeding rates are necessary when we introduce cleated traffic to a turf stand. We don’t hesitate to recommend turf managers putting out an initial rate of at least 20 lbs/1000 ft2 when starting from bare ground to get as much wear tolerant biomass established as possible before traffic starts. This method of seeding at higher rates can also result in an essentially weed free stand of grass, especially with a quickly establishing grass like perennial ryegrass.

Moss & Algae control: Dr. Minner gave a good overview of the different types of moss and algae that can inhabit bentgrass putting greens, or anywhere conditions are right for their growth and development (wet, low mowing height, high N). He also showed preliminary results of a study that uses different methods and chemicals to control silvery thread moss on greens. Two products, MossBuster, and QuickSilver herbicide (carfentrazone), which has labeled rates and instructions for silvery thread moss control, are being evaluated both in combination with each other and on their own at different rates to determine the most effective control of silvery thread moss.

The main problem with the MossBuster product is that it can have an extremely phytotoxic effect on bentgrass, however, it is extremely effective in killing silvery thread moss. Conversely, QuickSilver is effective, but not as effective as MossBuster at finishing off moss populations. So far, a low rate of MossBuster combined with a low rate of QuickSilver, applied frequently (1 week apart), has shown the least phytotoxicity and the moss control is on par with higher rates of each product in combination or on its own. This study is still relatively new and we will continue to monitor the effects of each treatment.

Apps for turf managers: Dr. Marcus Jones has been watching the turfgrass technology front very closely over the past few years and was able to give attendees a short discussion on a relatively new ‘App’. The iStimp is an app that claims to act as a stimp meter on golf greens and is available for Apple devices including the iPod touch, iPhone, and iPad.

Essentially, you set the ball in the small divot of the ‘home’ button on the iPhone, set it on the ground, and lift up until the ball starts to roll. Once the ball has rolled its distance, you use a built in ruler to measure the distance. The phone then calculates what the reading would be on a regular stimp meter. Dr. Jones is working on a research project that will test the effectiveness of this app when compared to the traditional stimp meter. Keep tuned to the iaTURF blog for updates on this project.


GPS spraying: GPS based technology has been around the agriculture field for a few years now and it’s slowly starting to creep its way in to the turf industry. We were fortunate to have a few of the current models on the market present at field day this year. We also saw a demonstration of how the technology works; the sprayer can minimize drift, minimize overlap, steer itself, calculate exact rates of application, and many other things. It’s truly an amazing technology and it probably won’t be long before everyone has some sort of experience with one of these machines.


If anyone has any questions or comments about Field Day 2011, please feel free to contact me, Andrew Hoiberg ( or any of the other speakers. This truly was one of the best field days I’ve been a part of and we owe it to a great turfgrass industry in Iowa. Thanks to the vendors and attendees for a wonderful day! We’ll see you next year!

Andrew Hoiberg
Graduate Student
Iowa State University


The importance of high-quality seed

October 10, 2013

Turfgrass establishment from seed can be a challenging endeavor. One key to successful establishment is the use of high-quality seed that is best adapted to each individual site. In the turfgrass industry, there are mixtures and blends of seed. A mixture is a combination of multiple species, while a blend is a combination of cultivars within the same species. For example, Kentucky bluegrass and perennial ryegrass in the same bag of seed would be a mixture of seed. However, a blend is a combination of cultivars of the same species such as Midnight and America Kentucky bluegrass. 


Seed Labeling Information

In most cases, the seed label is the best source of information pertaining to seed quality. By law, each seed package sold in the US must be labeled truthfully. However, labeling does have its downfalls and all consumers must be aware of the potential loopholes. There are no bargains when it comes to turfgrass seed. For a higher quality seed, you will have to spend a few more dollars. The availability of high-quality seed is limited and ultimately expensive to produce, which has led to the production of poor-quality seed.

The germination percentage should also be considered when purchasing seed. Seed should never have labeled germination rate below 85%. In addition to the labeled germination rate, time also play a huge factor in germination percentage. Seed germination decreases over time and germination rates may have decreased significantly since the original testing date. 

The percentage of inert matter tells you the weight of all nonseed material in the bag. Weed seed percentage is very important and is the total weight of all the weeds. In most cases, noxious weeds are of little concern in turfgrass because of the continuous mowing and defoliation following germination. Quackgrass is one of the few exceptions. 

The biggest loophole and seed contamination occurs in the percentage by weight of other crop seeds. Most of the worst weeds in turf are perennial grasses. Most of these perennial grasses are produced commercially, which group them into the other crop seed category rather than noxious weeds. Grasses such as bromegrass and tall fescue are particular problems. The species list of “other crops” is not usually listed on the label and it is hard to identify their potential impact in turfgrass seeding. To prevent issues you should always use high-quality seed from a reputable dealer. There are no bargains in seed and it is advisable to pay more now because it will save you money and headaches in the long-run. 

One example of this can be seen below with a yard contaminated with common perennial ryegrass. Common perennial ryegrass is usually found in cheaper seed mixes. It is produced at a lower cost than many of your elite perennial ryegrass cultivars. The common perennial ryegrass can be unsightly and drastically reduce turf quality. It has many of the same identification characteristics that you would consider a more desirable perennial ryegrass to have. Folded vernation (once closely observed from a microscope), short to midsized auricles possible, bunch type growth, potential red stem base (is absent in pictures below), divided collar, and a pointed leaf blade that rolls out of the sheath. Common perennial ryegrass however lacks the allure features of the more elite perennial ryegrass cultivars. It often grows awry and is perceived as a nuisance and weed species as seen in the pictures below. 


Establishing a Lawn from Seed

January 17, 2014

The establishment of a home lawn from seed can be challenging. The keys to successfully establishing a lawn from seed are selecting high quality seed, seeding at the optimum time, and following proper establishment procedures. Today’s blog is a revised Iowa State University extension publication on establishing a lawn from seed. 

The following is a small introduction to the publication.

Time of Seeding

The best time to seed a lawn in Iowa is between mid-August and mid/late September. However, lawns can be successfully established as late as late-September in central Iowa and early October in southern Iowa. Late summer planting is preferred to spring seeding because seeds germinate and grow rapidly in the warm soil. The warm days and cool nights are ideal for seedling growth.

Establishment from seed in the spring is possible when irrigation is available. However, lawns established in spring often become infested with annual weeds unless preventive steps are taken. A pre-emergent herbicide such as siduron or mesotrione should be applied to the area during a spring establishment. Most of these preemergent herbicides kill the seeds of the cool season lawn grasses and cannot be used at the time of seeding. Mesotrione and siduron are the only exceptions. Siduron can be applied to areas seeded with Kentucky bluegrass, fine and tall fescues, and perennial ryegrass. Siduron selectively control weedy annual grasses, such as crabrass, foxtail, and barnyardgrass, while allowing the desirable turfgrasses to grow. Siduron is the active ingredient of many crabgrass preventer/starter fertilizer materials. Once the barrier of siduron has been established, the soil should not be further disturbed. Wherever the barrier is broken, annual weeds will emerge. Mesotrione is labeled for preemergent use only on newly seeded Kentucky bluegrass lawns to help control crabgrass seedlings and other annual weeds.

The entire extension publication is attached in pdf form. To download the publication, click on the following link Establishing a Lawn from Seed


Turf Club Seeding at Reiman Gardens

September 26, 2017

The Iowa State Turf Club recently completed a fundraiser and learning experience at Reiman Garden's. The students helped Reiman Garden's by seeding an entry area that has been under construction for the past year. The seed used was a 70% Kentucky bluegrass and 30% perennial ryegrass mixture. The students also were allowed to experience hydroseeding with the help of the campus services. The area will also serve as a demonstration in varying seeding rates and establishment methods for the student's to track throughout establishment. The warmer temperatures recently have created excellent conditions for the perennial ryegrass to germinate, especailly in the higher seeding rates under the hydroseeded area's. 

Turfgrass area hydroseeded by the turf club.
Hydroseeding completed by the turf club at Reiman Garden's

Turfgrass student's seeding at Reiman Gardens
Turfgrass student's seeding at Reiman Gardens on Sept. 13. 

One week after seeding the turfgrass is germinating.
One week after seeding, much of the perennial ryegrass is germinating. This is especially true on the hillsides that were hydroseeded at an increased seeding rate. 


Update on New Sports Turf Research Area

September 14, 2015

Here is an update on the new sports turf research area at the Horticulture Research Station at Iowa state.  It is a time lapse from May 1 until the 2nd week of September.  Everything is now seeded and the new grass is coming in fast.  Dan was able to mow some of it this week.

If anyone would like to stop out and see it, let me know.




May 10, 2012

Here is a follow up on a post from March 12 about a late seeding of bentgrass on tees in the Chicago area.  My son Tim is a superintendent there at Makray golf club there.  He seeded the tee in the first picture below on Oct. 25, 2011 and covered it.  He had great results and nearly complete cover on March 12 when he pulled off the covers. 

Pictures 2, 3, and 4  below are of new tees seeded on March 12.  All 4 pictures were taken on May 10.  He is planning on opening them May 11 for play.  In a normal year, I tell people that if they get bentgrass seed in my mid-September, they will probably have to wait until early June to open.  If we keep getting these mild winters and warm springs, I may have to change that recommendation.

Picture 1.  Tee seeded on Oct. 25, 2011.

Tees Seeded


Pictures 2, 3, and 4 were seeded this spring on March 12.  All tees will go into play on May 11.

Tees Seeded

Tees Seeded

Tees Seeded



April 10, 2012

With the warm weather that we have had, people have been asking about whether they should seed now or wait a few weeks.

Spring seeding is hard, no matter when you do it. Spring seedings often turn to crabgrass and other annuals and may take a year to mature into a real lawn. You can use a selective preemergence herbicide called Siduron which will selectively kill the annuals and let the perennials like Kentucky bluegrass and perennial ryegrass emerge, but that is expensive and difficult.

The best time to seed remains late summer to early fall. I would set August 15 as the best time to plan your seeding in central Iowa.

If you must spring seed, give it a little time yet. I am currently telling those who contact me to wait until after May 1. As we saw this morning, we are not past the frost-free days yet. Seedlings, particularly perennial ryegrass, can be susceptible to cold temperatures in the spring.

If you have to spring seed, I would recommend the application of Siduron with the starter fertilizer to control the annuals. If you end up with a lawn of crabgrass, don't give up. The perennial grasses will be in there. The annual will die in the fall and next spring you can put on a standard preemergence herbicide to control them.

Other standard preemergence herbicides will not work at the time of seeding. They will kill the crabgrass, but they will also kill the grasses that you are trying to seed.

The new herbicide Tenacity (mesotrione) can be used for spring seeding of Kentucky bluegrass, but leave that to the experts. Your local lawn care professional can tell you more about the product.