Annual Bluegrass
Poa annua · Cool-season, Annual (rarely short-lived perennial), C3
Grass Family
Poaceae, Subfamily Pooideae, Tribe Poeae
Grass Category
Invasive/Weed Grass, Sports Turf, Golf Course Grass
Variety / Cultivar
Common Poa annua (wild type)
Hardiness Zones
USDA Zones 3-10; excellent cold tolerance but dies off during summer heat (above 85°F/29°C) in many regions.
About This Grass
A light-green, low-growing grass with a tufted habit. It is most distinct for its ability to produce prolific seed heads even at extremely low mowing heights (down to 0.1 inch). It typically grows 1 to 12 inches tall if left unmowed.
Blade Characteristics
Fine to medium width (2-3mm); flat or slightly folded; prominent boat-shaped tip; light lime green color; folded vernation; long, thin, silvery-white membranous ligule; auricles absent; smooth blade with two distinct 'railroad track' veins down the center.
Root System
Shallow, fibrous root system; low thatch tendency; very fast establishment from seed; poor drought tolerance due to shallow roots; forms a weak sod that easily pulls up.
Growing Information
Origin Region
Native to Europe and Eurasia, now cosmopolitan worldwide in temperate climates
Growth Habit
Bunching to low-growing spreading mat; can produce short stolons in some biotypes
Sunlight & Water Needs
Full sun to heavy shade; high water requirements; prefers moist to over-saturated soils; poor drought tolerance; thrives in compacted soils with high phosphorus.
Mowing & Maintenance
Ideal height 0.5-2.0 inches but survives at 0.1 inch; very frequent mowing; requires high nitrogen in spring/fall; high maintenance due to disease susceptibility.
Special Characteristics
Extreme seed production (up to 360 seeds per plant); very high shade tolerance; low wear tolerance but high recovery speed; susceptible to Dollar Spot and Pythium.
Ecological Information
Introduced/Invasive in North America; provides some forage for small birds but generally considered a major nuisance weed in turfgrass systems; pioneer species in disturbed soils.