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Bermudagrass is Taking Over The Transition Zone


Q. HELP!!! How can I get rid of Bermudagrass permanently? Last year, we killed our Bermuda-infested lawn with Roundup, left it alone over the winter, and then tilled it up and planted new seed this spring. But the Bermuda is back and spreading again! What can we do?
    ---Kathy in Gaithersburg, MD
Bermuda has completely taken over the yard on one side of our house, the side that gets less sun. It looks pretty at times when seen from a distance, but I wouldn't call it a lawn grass. How can I get rid of it and keep it from coming back?
    ---David in Sterling, VA
How do I rid my lawn of Bermudagrass? Moving is not an option!
    ---Robert in Woodbridge, VA
A. It is no coincidence that all of our questioners live in the Washington, DC area—which our lawn care expert, Dr. Nick Christians of Iowa State University (the researcher who discovered the 'weed and feed' potential of crabgrass-preventing corn gluten meal), explains, "is a region that pretty much defines the Transition Zone."

A short lawn grass primer: As we often explain, two basic types of lawn grasses are used in the United States:
  • Cool season grasses like fescue, rye and bluegrass that thrive when temps are normal to cool, but that are greatly stressed by summer heat.

  • Warm season grasses like centipede, Bermuda, St. Augustine and Zoysia that thrive in summer heat but die off or go dormant in winter.
So that's easy, right? Use cool season grasses in the North; warm season grasses in the South. Ah, but the brightly-colored maps that illustrate each region's preferred turf type have a dark shadow called 'the Transition Zone' that hovers over a large swath of the nation—roughly from the bottom of Pennsylvania down to the Carolinas and West to include all of Oklahoma and most of Kansas. 100% of Missouri, Arkansas, Tennessee, Kentucky and the Virginias are all trapped inside the zone, where the summers are often too hot for cool-season grasses and the winters too cold for warm-season grasses.

Nick explains that "homeowners in the Transition Zone usually have to choose the lesser of two evils; either a grass that's green in the winter but is very much at risk of burning up in the summer, or a turf that thrives in summer, but goes tan and dormant over the winter."

At least that was traditionally the choice. Nick adds that "whatever the cause, our average temperatures are definitely increasing—making it more difficult to maintain cool-season grasses over the summer in the Transition Zone. But Bermuda grass LOVES a hot summer; and it's been deliberately planted in the DC area over the years," he continues; "so it can pop up almost anywhere".

I thought that DC winters were too cold for Bermuda…

"It won't survive winter a lot further North," explains Nick; "zoysia is the only warm-season grass that can survive in the upper tier of the county. But Bermuda is perennial in most parts of the Transition Zone. And," he adds, "it's a very aggressive grass. It spreads rapidly, tolerates shade well, and can come up on the other side of a 12-inch deep barrier."

And many homeowners in the Zone make it easier for warm-season grasses to move in by caring for their cool-season lawns incorrectly in summer. If you want a cool-season grass to be able to at least try and compete with an invader like Bermuda, it should never be cut below three inches, should be fed only in the Spring and Fallnever in the summer—and should only be watered deeply and infrequently. Cut it too short, shock it with fertilizer when it's already heat-stressed and/or water it for short periods of time frequently and it won't have a chance. (But warm-season grasses thrive with summer feedings and a short cut.)

So—what's a lawn owner with invading Bermuda to do?

"Make peace with it," says Nick. "Yes, it goes dormant over the winter just like zoysia, but the more the climate heats up, the more it becomes the successful grass in the Transition Zone. If you don't like the type or texture of the Bermuda that's taking over your lawn, tear it up and replace it with an improved variety next Spring.

"The time of year any kind of lawn is installed is crucial," stresses Nick. Warm-season grasses are best installed in the Spring; cool season grasses in the Fall. That's one reason the Bermuda came back so quickly on the people who said they tore up and replanted their lawn. They specified that they sowed new cool-season grass seed in the Spring, and that rarely works—especially if there's any Bermuda left in the soil, and there almost always is some left behind.

"To try and install a new cool-season lawn, you'd first have to have the old turf chemically sterilized to kill the Bermuda—which costs a fortune, must be done by a licensed professional, uses the kind of chemicals that Mike has been railing against for the past two decades, and ignores the fact that the climate is greatly favoring warm-season grasses in these regions.

"Even when people don't mind using chemical herbicides, I strongly advise going with a warm season grass in these situations," concludes Nick. "Because no matter what you do, in the long run my money's on the Bermuda."

Final notes from Mike McG: If you still want to try and kill a warm-season grass like Bermuda and install a new cool-season lawn, try solarizing the old turf instead of chemical sterilization. (You'll find all the details on solarization in this previous Question of the Week.) And then be sure to sow the seed of a grass designed to survive in the Transition Zone at the correct time of year: August 15th through September 15. You'll find complete directions on installing a new cool-season lawn HERE.)

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