Annual Bluegrass
Poa annua · Cool-season, Annual (though occasionally acts as a short-lived perennial), C3 grass
Grass Family
Poaceae, subfamily Pooideae
Grass Category
Invasive/Weed Grass, Lawn/Turf Weed
Variety / Cultivar
Common wild type (no specific turf cultivar)
Hardiness Zones
USDA Hardiness Zones 2 through 10, wherever cool, moist conditions prevail during its active growing season.
About This Grass
A light green, low-growing grassy weed that often forms unsightly patches in lawns and golf courses. It grows rapidly, produces abundant whitish-green seed heads even at very low mowing heights, and turns yellow or brown under summer heat or drought stress.
Blade Characteristics
Blades are medium-width (2-4mm), flat or slightly folded, light green to yellow-green, with distinctive parallel sides and a characteristic boat-shaped tip. Vernation is folded in the bud. Ligule is membranous and prominent; auricles are absent.
Root System
Shallow, fibrous root system with low drought tolerance. It establishes extremely fast from seeds, which allows it to quickly colonize thin or damaged turf areas.
Growing Information
Origin Region
Native to Europe, now widely naturalized throughout temperate regions worldwide
Growth Habit
Bunch-type that can form loose mats, spreading mainly by prolific seed production rather than aggressive rhizomes or stolons
Sunlight & Water Needs
Thrives in full sun to partial shade, particularly in damp or compacted soils. High water requirement to stay green in summer; low drought tolerance and enters summer dormancy or dies back quickly in hot, dry weather.
Mowing & Maintenance
Can survive very low mowing heights (often setting seed below mower blade height). High maintenance if trying to eradicate; generally considered an invasive weed in managed turfgrass.
Special Characteristics
Extremely prolific seed producer capable of setting seed under almost any mowing height. Low wear tolerance, poor heat tolerance, and susceptible to various diseases like summer patch and dollar spot.
Ecological Information
Introduced species often considered a weed in cultivated lawns and turf. Provides minimal wildlife value compared to native species and can outcompete desirable turfgrasses in damp, compacted, or over-watered soils.