Rough bluegrass is a cool season grass that is often present in lawns as a weed. It creates large patches of apple-green turf that thrives in wet, shady spots but as soon as the air and soil temperatures get into the 80's, it goes into summer dormancy. Keeping the grass watered will somewhat stall dormancy, but inevitably it is the heat that causes the plant to shut down. Dormant rough bluegrass looks like straw-colored circular patches of dead grass and is very often misdiagnosed as a turf disease. Just this past week, three lawn samples have been sent to OSU's Diagnostic Clinic. Close inspection of the turf reveals matted down leaf tissue and stolons that smells musty. Underneath the matted-down turf, short light green shoots may be visible.

Once temperatures cool down in the fall, rough bluegrass comes out of dormancy and returns to it's usual vibrant and aggressive growth. Control of rough bluegrass is difficult and requires repeat applications of a non-selective herbicide, followed by seeding with more desirable grass seed.

OSU Extension Factsheet SRT-3-05: Annual and Rough Bluegrass Control