Rough Bluegrass is Going Dormant

With 2-inch Soil Temperatures Close to 80°F, Rough Bluegrass is Closing Down for the Summer

With the air temperatures in the high 80's/low 90's and soil temperatures at a 2-inch depth of close to 80°F, rough bluegrass (Poa trivialis) is now going dormant on athletic fields, home lawns and golf courses. Rough bluegrass is a cool-season grass best adapted to growing in air temperatures of 60-75°F and soil temperatures of 50-65°F. Once temperatures get hot (usually end July/mid-August) in central Ohio, rough bluegrass goes dormant/brown until more favorable weather returns.

Many times rough bluegrass is mistaken for another problem, such as a disease or burn caused by a fertilizer spill. See the pictures below for some classic characteristics of rough bluegrass in a dormant state.

Brown patches can be as small as a baseball or as large as this one, pictured left. Patches are irregularly shaped and there will be no sign of disease, such as mycelium.

In this case, the majority of the turf on the football field was rough bluegrass so when it went dormant it created major problems. Irrigating these patches will not bring this turf out of dormancy - soil and air temperatures need to decrease before recuperation occurs.

The turf is laid over, matted down and straw colored.

Upon closer inspection, the matted turf smells musty. Digging around underneath, green shoots/leaf tissue may be visible. This leaf tissue will re-grow with more favorable temperatures this fall.
Control options are limited at best. There is no selective chemical control for rough bluegrass on atheltic fields or home lawns. After the playing season, areas could be killed with a non-selective herbicide like Roundup (Glyphosate) and re-seeded with more desirable grass. Even then, the rough bluegrass may return because it grows so aggressively in spring and fall. One option that can work is to core aerate and heavily overseed those dormant turf areas right now with perennial ryegrass. Over time, the perennial ryegrass will out compete the rough bluegrass .

For more details on rough bluegrass identification and prevention, read the Ohioline Extension Factsheet: Annual Bluegrass and Rough Bluegrass Control

Authors: Pam Sherratt & John Street