Annual bluegrass (Poa annua) is a cool-season, annual grass that spreads by seed. Annual bluegrass has a tufted habit with a bright green leaf color and fine texture. Annual bluegrass seed germinates in late summer/early fall once soil temperatures fall below 70° F. Seedlings grow and mature in fall, overwinter in a vegetative state and produce seed in spring. Annual bluegrass is a prolific seed producer and individual plants may produce hundreds of viable seed, even when closely mowed. Annual bluegrass flowers over several months in spring and produces seed that may remain dormant in soil for years before germinating. Annual bluegrass grows well under short day lengths and cool conditions, and may out-compete other turf species during late fall and early spring. Annual bluegrass often dies from summer stresses but may survive if irrigated and if pests are adequately controlled, especially for perennial biotypes. Before starting a weed control program, homeowners should realize that complete eradication of annual bluegrass (or any weed) from the landscape is not practical. A more realistic approach is to manage (not eradicate) the weed by reducing the infestation to a tolerable level.
For more information and control options refer to UGA Extension Bulletin 1394: Annual Bluegrass Control in Residential Turfgrass.