Dig in with the Master Gardeners
It has been a slow, cold spring in Delaware County. Lawns all across the county lay dormant well into April, waiting for the right conditions to break dormancy and begin to grow. Finally, we’re recovering from the one-two punch of last year’s hot, dry, long summer and cold, snowy, long winter. Our lawns are finally turning green and we can see what lived through the tough weather.
A lot of lawns around the county had brown patches of dead-looking grass this spring. In some cases, these were in areas that seemed green and lush when the rest of the lawn was really struggling last year. In drought-stricken summers, when your turf is really struggling, “warm season” and annual grassy weeds sometimes get a chance to thrive. Crabgrass, foxtail, quackgrass, and nimblewill were all invading and enjoying the heat and lack of competition last summer. As homeowners tried to beat the heat with extra watering, nimblewill got its ideal conditions of moisture and heat while the bluegrass, ryegrass and fescue was protecting itself by lying dormant.
Simply driving across the county this spring, I saw many big, tan patches of nimblewill (Muhlenbergia schreberi). “Nimble Will” is a mat-forming, warm season, perennial grass. Like the common names of many weeds, he gets a nickname based on his growth habit. Over the course of the season, this nimble grass will practically somersault across a lawn if conditions are right.
Nimblewill will start by seed. As a warm-season grass, it likes to start in a warmer soil temperature than our lawns, which are cool-season grasses. In the early part of its life, the blades of nimblewill are short and upright. This early growth is a lush green, so it blends right in with the rest of the grass in your lawn. This time of year, when you mow at least once a week, you often won’t see new patches of it at all.
However, as the plant matures the growth pattern changes. The stems bend over and lay on the ground. These stems will actually take root and begin to send up new, shorter leaves. Before you know it, you have a dense, low growing mat of this grass forming. The mature leaves are a gray-green color. It gets easier to see, the older the plant becomes. These patches will be a distinctive tan color from the first hard frost until well into late spring.
Many people mistake this tan patch in their lawn for signs of grub damage in the early spring. To test for grub damage, the old “field test” is to grasp the grass and give a little tug. If it comes up easily, like a carpet, the wisdom is that you might have grubs. This advice is certainly a good way to check in July or August, when grub damage combines with heat and drought stress to kill portions of the lawn. Testing for grubs in this way is best done before the first hard frost in the fall, before warm-season grasses go dormant for the winter.
If dormant nimblewill got established last year, it would have formed a dense mat. That mat of grass has a weak, fibrous root system. Once it gets cold, this grass pulls up very easily, especially when dormant. So, if you go out and tug on a patch of this grassy weed while it is still brown, you’ll get handfuls of it. Large, mat-like areas will come out of the ground with little effort. Just because a mat of grass is brown and gives you no resistance does not mean you have grubs, especially if you saw no sign of problems in that area last year. If it was green until frost, it is much more likely a grassy weed.
For more information, visit oardc.ohio-state.edu/weedguide/singlerecord.asp?id=90 or ohioline.osu.edu/hyg-fact/4000/4002.html.
Wendy Wolpert is an OSU Extension Delaware County Master Gardener Volunteer.