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Fall Maintenance: Undertaking Overseeding

| Landscape

It?s fall and that means it?s time to overseed bermudagrass in the South and Southwest. The main reason for overseeding, of course, is to provide your clients with attractive, green grass during the winter months. To accomplish this, the process of overseeding is fairly straightforward: get as much cool-season grass seed to contact as much soil as possible without harming the permanent bermuda. But, as you may know, there can be trouble along the way, like inconsistent germination or growth, too much required maintenance, or a less-than-smooth transition back to bermuda come spring. Here?s a look at the latest approaches to the age-old practice of overseeding, from the cool-season grass you select to the most effective cultural methods applied today.

The ever-popular perennial
When overseeding first became popular in the 1960s, annual ryegrass was the cool-season species of choice. It establishes quickly, grows voraciously and transitions fairly well. But, annual rye was found lacking in overall turf quality and required a good deal of mowing. In the 1980s and ?90s, seed companies addressed this issue by offering ?intermediate ryegrass,? a cross between annual and perennial ryes. But the result was turf that was uneven in texture and inconsistent in color.

Since that time, the popularity of perennial ryegrasses as the single species for overseeding has soared. Like annual rye, perennial rye delivers fast establishment, but it also offers a fine leaf texture and overall aesthetic appeal, competitiveness, low maintenance and tolerance of close mowing. To meet the demand, seed breeders keep introducing even better varieties that offer superior turf quality, deeper green color, quicker establishment, wear and cold tolerance, better mowing qualities, and strong disease and pest resistance.

?Where perennial rye is really getting interesting is in spring transition,? says John Rector, a turfgrass consultant for Turf-Seed, Inc., an Oregon-based seed company. ?Through extensive hybridization and selection programs, breeders are identifying perennial ryes that have poor heat tolerance and thus will transition more quickly.?

Seed companies are also offering more perennial ryes with improved salt tolerance, a boon for desert areas of the Southwest, where well water is often used for irrigation. And, if the use of effluent water becomes as prevalent in the future as predicted, these perennial ryes will be in demand.

?The sophistication of seed producers today is just incredible,? says Don Schlander, vice-president of maintenance at Grounds Control, Inc., (formerly Terrain Systems) in Phoenix, Arizona. ?I?ve been amazed at the options in the last couple of years. You want quick germination, you want it to stay long and you want it to decline when the warm weather comes on? You can have it all, and at prices I?ve never seen so low. In fact, we?re paying about 30 percent less today than we paid in 1999.

?Sure, annual rye is even cheaper, but it?s false economy to save money on seed and then spend more money on maintenance and labor later on,? he says. ?Perennial rye is the only way to go.?

John McShane, president of Stover Seed Company in Los Angeles, agrees. ?With perennial rye being such a great value, better quality and easier to maintain, it makes sense to use it instead of annual rye,? he says. ?If the industry wants to continue enjoying the quality of innovations and improvements, we have to support it and not just buy on price.?

Quality counts
For a listing of the best and brightest of these varieties, take a look at the latest National Turfgrass Evaluation Program (NTEP) results at the www.ntep.com.

?There are an awful lot of very good perennial ryes out there now, and any of the top one-third mentioned in the NTEP results are suitable,? adds McShane. ?These results are a great tool that a contractor can use for determining quality.?

Regarding quality issues, both McShane and Rector advise that every landscape professional be able to understand the label on a seed bag to identify potential problems. First, look for any kind of mixture of annual ryegrass with the perennial, which, as we?ve learned, will compromise the overall quality of the grass. Under ?crop seed,? you should find that the seed includes less than three percent of annual rye.
Also check that the variety of the species is stated. There are a lot of products that are ?VNS? grasses (variety not stated), but, according to Rector, you could be buying a grass that was introduced 20 years ago.

?It takes a lot of time and effort to prepare, irrigate and fertilize any turfgrass, so why not make sure the outcome will be worth all the effort?? asks Rector. ?Work with a reputable supplier, know what you?re buying and you?ll reap the benefits.?

Time is of the essence
Once you?ve selected quality seed, the next step is to plan for seedtime ? the season of sowing. As you may already know, sowing the seed too early can cause germinating ryegrass to compete with still-flourishing bermudagrass, and thus establish poorly. Done too late and the rye may not have time to establish and grow before colder temperatures and shorter days arrive. In California and Arizona, the best time to overseed is roughly from mid-October to mid-November, and slightly earlier in Nevada. For Texas and the sunbelt states, this schedule may vary slightly.

However, even the best-laid plans can go awry. What if the fall is unusually warm, delaying dormancy? Or, what if a client wants to get a jump on the season and start reseeding earlier than the optimum time? A good solution may be Turflon Ester, according to John Law, director of technical services with ValleyCrest Landscape Maintenance, (formerly Environmental Care) in San Jose, California. Dow AgroSciences? Turflon is the turf application of triclopyr and it is designed to slow the bermudagrass down, shifting the competitive advantage to the rye for quicker establishment, without damaging the bermuda.

Law suggests using four ounces per acre applied one week before overseeding and, if necessary, again three weeks after overseeding. Be sure to apply the Turflon before scalping the bermuda.

Out with the old
In the last few years, there have been some important changes in approaches to certain commonly held overseeding practices. To reduce heavy thatch, for example, turf managers often aggressively verticut the grass just prior to overseeding. However, studies have shown that damage can occur to the bermudagrass and cause a slow spring transition. The verticutting process cuts up stolons and crowns, and, if done deep enough, could sever shallow rhizomes.

If you need to de-thatch, do it in late June, according to Law, a time when bermudagrass can best recover from any kind of punishment. This way you have 12 weeks of full-on bermudagrass growth before overseeding starts.

?Around June, we notify our clients that it?s time to begin a de-thatching program,? says Dale Micetic, senior vice president of Grounds Control.

?Even though this is an add-on, we?ve had great response and have been able to complete this step in plenty of time.?

During de-thatching, be sure the de-thatching blades are sharp to minimize tearing and mashing the bermuda, Law warns. And do not use a flail or spring-type de-thatcher. Cut just enough to open the canopy and allow the seeds to contact the soil.

?If you don?t care how the bemudagrass looks next summer, then heavy de-thatching is acceptable,? adds Law.

Another commonly held practice to avoid when preparing bermuda for overseeding is to completely stop irrigation to let the grass dry down.

?The traditional thought has been to turn the water off completely, let the bermuda turn completely brown and dormant, overseed and then turn the water back on,? says Schlander. ?Instead, after we start cutting lawns down, we cut the water in half, not completely off. Phasing down the water lessens the stress on bermuda.?

Law agrees. ?It?s far better to cut back about 50 percent of the water you normally use and to do so about two weeks prior to overseeding,? he says. ?Letting bone-dry bermuda bake in the sun kills a lot of turf, which means the bermuda will take a long time to recover come spring.?

When you address the irrigation schedule, this is also a great time to inspect the sprinkler system for distribution uniformity. Rick Mutaw, maintenance supervisor with American Landscape in Canoga Park, California, advises that you check to make sure you have good coverage in all areas.

?You?re checking the precipitation rates on the heads and adjusting the nozzles as part of the ongoing process of maintenance,? he says. ?We check our irrigation at least every two weeks on all of our jobs.?
If your irrigation system forces you to overwater some areas to keep other areas from drying out, damping-off disease could be a problem for seedlings later, according to Law. Outside of a sprinkler-system renovation, Law suggests a preventive application of a fungicide.

Important to-do?s
The following are procedures critical during the process of overseeding:

  • Stop fertilization four to six weeks before overseeding.
  • Seed uniformly. Use a rate of 350 ? 450 lb/acre (8-10 lb/1000 sq. ft.) of seed.
  • Top dressing is optional, notes Law. If you choose to use top dressing, use no more than one-quarter inch of weed-free material, such as peat moss or forest mulch.
  • Water heavily (.25" ? 0.5") initially to move seed to soil and establish a soil moisture base. Law recommends light watering two to four times daily thereafter to keep the seedbed moist. As the turf matures, reduce the number of water cycles but increase durations.
  • Two weeks after overseeding, when the grass is about two inches, mow down to 1? inches.

Hello spring, goodbye rye
Ideally in late spring, the perennial rye will completely disappear just as the bermuda has fully greened up. If you?ve overseeded with some of the latest varieties of perennial rye and avoided excessively disrupting the bermudagrass during the fall, spring transition should go well. The bermudagrass will have more growing points and more stored energy to grow back from. But are there additional steps you can take to help?

?Various cultural practices, such as spiking, verticutting, aeration and various mowing regimes do not seem to make much difference,? says Law. ?How badly the bermudagrass is beat up in the fall will determine how well it makes the transition in the spring. Beware of anecdotes about a great transition method that was really due to favorable weather a particular year.?

Also, herbicides for transition are controversial. They are known to damage the bermuda, such as with stunted growth and twisted leaves.

?When it comes to spring transition and overseeding in general, I can?t emphasize enough how important it is to have thought long-term during the fall,? says Micetic. ?Plan ahead, keep your clients abreast of what?s needed, and keep yourself current with the latest practices.?

October 2002

 
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