Scientific Name: Poa annua

Common Name: annual bluegrass

Other Common Names: walk grass

Synonyms: Poa annua var. aquatica, Poa annua var. reptans

Habit: It is a clump-forming winter annual grass. It reproduces by seed that can germinate any time of year but predominately in the fall and less so in the spring and summer. Seed germination peaks soon after air temperature drops below 75 degrees F in early fall. Annual bluegrass produces white seedheads in spring and early summer and can decrease aesthetic value of turfgrass. Annual bluegrass is well known for its ability to tolerate low mowing heights on golf greens.

Leaves: Leaves are light green, lack hairs, lack auricles, are narrow with pronounced mid-vein, and have a membraneous ligule that is pointed. Leaves are creased because they are folded in the butt and leaf tips are boat-shaped , which is characteristic of the genus Poa. It is also common for annual bluegrass leaves to have wavy margins toward the leaf base. Upon close inspection, leaves have two indented valleys along each side of the mid-vein which are offset from the center of the leaf. These double indentations are often referred to as railroad tracks.

Identifying Characteristics: Boat-shaped leaf tip, pointed membranous ligule, folded in the bud, lacks auricles, and does not produce rhizomes or stolons.

Flower Seed Head: Seedhead is an open panicle in the shape of a pyramid. Seedheads are borne on short stalks and are white. Often plants will impart a white sheen to infested turfgrass areas during the spring when seedhead production peaks. Each spikelet in the panicle is about 4 to 6 mm long and produces 2 to 6 flowers/seed.

Seed Fruit: Flowers can produce viable seed within one day of germination. Seed mature to a light brown color and are typically 2 to 4 mm long and 2 mm wide.

Where Found: A common weed of fine turfgrass, annual bluegrass actually ranges from extremely wet to extremely dry and very cold to very hot environments. The plant is found on every continent but thrives in cool humid regions. Numerous biotypes of annual bluegrass have been selected by environmental conditions and human practices due to the enormous reproductive and adaptive potential of this species. Annual bluegrass is a desirable turfgrass in some cool-humid areas and tolerates close mowing as on golf putting greens

  • Life cycle: winter annual

  • Plant type: Grass

  • Auricle: not present

  • Plant family: Poaceae

  • Leaf arrangement: folded in bud

  • Hair surface: no hairs

  • Ligule: membrane

  • Seed head: panicle

  • Width: less than 5 mm

  • Grass stem: flat or oval