Steve Dewey, Utah State University, Bugwood.org
Annual bluegrass is one of the most common weeds in the country and can be found everywhere from residential lawns to golf courses and sports fields. This weed begins to show up in the spring and germinates once the fall temperatures fall below 70 degrees. The winter annuals will die off while the seeds stay in a dormant state in the soil until the next spring.
Annual bluegrass can grow in most any turf whether it's high or mowed short. It's difficult to control but can be managed in a lawn with thick, healthy turf. Keeping the soil phosphorous levels in the low to medium range helps, as does using a postemergent herbicide on newly developed weeds. Applying a pre-emergent herbicide before the spring will significantly help to control annual bluegrass.