Annual Bluegrass (Poa annua)
Poa annua · Cool-season, Winter Annual (sometimes short-lived perennial), C3
Grass Family
Poaceae, Subfamily Pooideae, Tribe Poeae
Grass Category
Invasive/Weed Grass (often found in Lawn/Turf and Golf Course Greens)
Variety / Cultivar
Not applicable (Wild type; specifically the annual form, Poa annua f. annua)
Hardiness Zones
USDA Zones 2-11; survives cold winters as seed; dies out in extreme summer heat/drought; thrives in cool, wet spring/fall weather.
About This Grass
A light-green, low-growing grass characterized by prolific seed production even at low mowing heights. It appears as bunchy, yellowish-green clumps that stand out against darker turf. Seed heads are small, branched panicles, whitish or light green in color.
Blade Characteristics
Blade width: fine to medium (2-3mm); shape: flat or slightly folded; tip shape: boat-shaped; color: light yellow-green; vernation: folded; ligule: conspicuous, white, membranous, and pointed; auricles: absent.
Root System
Shallow, fibrous root system; lacks significant rhizomes or deep roots; very low drought tolerance; prone to easy pulling from the soil.
Growing Information
Origin Region
Native to Europe and Asia; cosmopolitan and naturalized globally in temperate climates
Growth Habit
Bunch-type/clump-forming; occasionally possesses short stolons or develops a low-growing mat under frequent mowing
Sunlight & Water Needs
Full sun to partial shade; prefers moist to over-watered conditions; high water requirement; survives well in compacted, damp soils.
Mowing & Maintenance
Height: adapts to any height (0.1 inch to 4 inches); maintenance: high (requires heavy control efforts or specialized herbicides); high fertility needs; prolific seed producer.
Special Characteristics
Extremely high seed production; shade tolerant; low wear tolerance compared to desired turf; highly susceptible to heat stress and fungal diseases like Pythium and Dollars Spot.
Ecological Information
Introduced/invasive; provides limited food for some waterfowl; displaces desired native or ornamental turf species; opportunistic colonizer of bare or compacted soil.