GREEN THOUGHTS: The many shades of bluegrass

BLUE SKIES AND GREEN LAWNS are part of the joy of June. Unfortunately, the more particular you are about your lawn, the more difficult life becomes. Those who treasure lawn diversity and think violets, plantains, dandelions and ground ivy are all okay have it easy—they just mow and go on to more fun things. At the opposite end of the spectrum, some folks demand grass-only lawns, and it has to be the right kind of grass, since there are some weedy ones. While bluegrass sounds desirable, when you get right down to it, there are actually undesirable bluegrasses, some of which can foil even the most valiant efforts toward lawn perfection.

I attempted to help a local homeowner (let’s call her Fern, just for fun) with such a case last week. In an otherwise extremely well-manicured landscape, her dark green lawn began to have patches of a yellow-green grass. The contrasting colors produced a polka-dotted appearance, far from the even-color desired. Fern asked a man at a garden center about it, and was told it was Annual Bluegrass (Poa annua). While this sounded good, Fern did some more research and was unconvinced. Although Annual Bluegrass (which can be perennial as well as annual, but that is fodder for another turf story) is light green, it should have seedheads this time of year. Fern’s grass had no seedheads, and seemed to be even paler than a picture of Annual Bluegrass. So she contacted Cooperative Extension for another opinion.

Careful examination of a sample revealed the grass’ true identity: Roughstalk Bluegrass, a.k.a. Poa trivialis. In a world where Kentucky Bluegrass (Poa pratensis) is king, some might think this other Poa trivial, but not so. Roughstalk Bluegrass was imported as a contaminant of pure Kentucky Bluegrass seed in the early 20th century, and has been in lawns ever since. It performs well in shady areas, likes moist, cool conditions, and spreads by creeping stolons. An enterprising scientist at Rutgers University, William Dickson, thought that Roughstalk Bluegrass could be useful. He elevated it from weed status in 1977 when the variety ‘Sabre’ was released for use in damp, shady lawns and to overseed golf courses for the winter in the south. Today’s newer varieties (such as ‘Darkhorse’ and ‘Quasar’) are reportedly better. I have yet to see a Roughstalk lawn, perhaps because local stores don’t sell the seed. Now available on the internet, it may be worth trying.

So what can Fern do to get rid of Roughstalk Bluegrass? No easy option exists. Individual patches could be dug up and removed, or killed with an herbicide, and the bare spots re-seeded. Roughstalk Bluegrass loves water and goes dormant when things dry out, so if we have a drought this summer, it will be weakened for fall renovation time. Chances are, despite any action, at least a little Roughstalk Bluegrass will persist, so Fern’s tolerance may be the best medicine.

To contact David Chinery, horticulture educator for Cornell Cooperative Extension of Rensselaer County, email

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