Annual bluegrass (Poa annua) occurs across the United States. It infests gardens, ornamental beds and turfs. The grass begins germination when soil temperatures fall below 70 degrees F in spring or fall. It attains a height of 6 to 8 inches. It grows well in moist soils and will not tolerate drought. Seed heads develop when the grass reaches six weeks of age. The seed production persists throughout the growing season, but is most prolific in the spring. A plant has the capability of producing 100 seeds in only eight weeks. Mowing offers little seed control because seeds emerge within a few days of pollination.
Avoid over-watering to kill shallow-rooted blue grass. Most turf grasses and ornamental plants can withstand a brief period of drought, and the stress it induces, but the blue grass is unable to tolerate drought well.
Apply a preemergent herbicide to kill seeds, such as prodiamine, benefin, pendimethalin, bensulide, dithiopyr or oxadiazon, before blue grass seed germination in late summer or early fall. Reapply the preemergent herbicide in mid-March or mid-April. Follow the directions on the label for application instructions. Use when the soil temperature dips below 70 degrees F.
Hand pick blue grass from ornamental beds before seeding. Promptly dispose of the pulled plants.
Spray blue grass using glyphosate or glufosinate in select spots. Follow the directions on the label for application. Take care not to let the herbicide come into contact with ornamental or native plants because the herbicide will kill them.