Annual Bluegrass
Poa annua · Cool-season annual (rarely short-lived perennial), C3
Grass Family
Poaceae, Subfamily Pooideae, Tribe Poeae
Grass Category
Invasive/Weed Grass, though occasionally used as golf course putting green turf
Variety / Cultivar
Common Poa annua; multiple biotypes exist including Poa annua var. annua (annual) and Poa annua var. reptans (perennial/creeping)
Hardiness Zones
USDA Zones 3-11; very cold tolerant but poor heat tolerance, often going dormant or dying during summer high temperatures.
About This Grass
Small, tufted, low-growing grass typically 2-8 inches tall. Noted for its profuse seed production and light-green to yellowish-green color. It forms dense, unsightly patches in uniform lawn turf. Seed heads are small, open, triangular panicles that appear even under very low mowing heights.
Blade Characteristics
Fine to medium width (1.5-3mm), soft, yellowish-green. Tips are distinctly boat-shaped. Leaves are folded in the bud (vernation). Ligule is prominent, white, and membranous. No auricles present.
Root System
Shallow, fibrous root system; lacks deep drought resistance. It does not form a strong sod and pull effortlessly from moist soil. Establishment is extremely rapid due to prolific seeding.
Growing Information
Origin Region
Native to Europe and Asia; cosmopolitan distribution, naturalized worldwide in temperate climates
Growth Habit
Low-growing, bunch-type to slightly spreading via short stolons; forms dense, light-green tufts that clump together
Sunlight & Water Needs
Full sun to partial shade; prefers damp, compacted soils and high moisture environments. Low drought tolerance; often dies back and turns brown during summer heat.
Mowing & Maintenance
High maintenance if used as turf; otherwise a weed that requires control. Can survive mowing heights as low as 0.1 inch. Frequent fertilization and irrigation promote its growth in golf greens.
Special Characteristics
Extremely high seed production; seeds can remain viable in soil for years. High shade tolerance compared to other bluegrasses. Low wear tolerance in summer, susceptible to Dollar Spot and Anthracnose.
Ecological Information
Introduced and widely considered an invasive weed in managed turf. Provides minimal wildlife value; often competes with native species in disturbed areas and moist transition zones.