Annual Bluegrass
Poa annua · Cool-season, Annual (though some biotypes are short-lived perennials), C3
Grass Family
Poaceae, Pooideae, Poeae tribe
Grass Category
Invasive/Weed Grass, Lawn/Turf, Golf Course Grass
Variety / Cultivar
Unknown (common wild type); exhibits prolific seeding even at low mowing heights
Hardiness Zones
USDA Zones 3-10; thrives in cool, moist spring/fall weather; susceptible to winter kill in extreme cold and heat death in summer.
About This Grass
A low-growing, bright yellowish-green grass characterized by its prolific, whitish branched seed heads (panicles) which appear even under frequent mowing. It forms dense, light-colored patches that contrast sharply with darker turfgrasses.
Blade Characteristics
Fine to medium width (2-3mm), soft texture, light yellowish-green color. Blades feature a distinct boat-shaped tip, folded vernation in the bud, and two prominent 'keel' lines along the midrib. Ligule is long, white, and membranous; auricles are absent.
Root System
Shallow, fibrous root system; lacks deep drought resistance. It establishes extremely fast from seed and can produce minimal thatch, but dies off quickly in high heat.
Growing Information
Origin Region
Native to Europe and Eurasia; widely distributed globally in temperate climates
Growth Habit
Bunch-type or slightly spreading via short stolons; forms dense, low-growing tufts
Sunlight & Water Needs
Prefers full sun to partial shade; requires frequent moisture and high fertility. Very low drought tolerance; often wilts or dies during summer stress without constant irrigation.
Mowing & Maintenance
Ideal height 0.5 to 2.0 inches; can survive at golf green heights (<0.125 inches). Requires high maintenance if managed as turf, or intensive chemical control if treated as a weed. High fertilization requirement.
Special Characteristics
Extreme seed production (up to 300+ seeds per plant), high shade tolerance for a turf grass, poor wear tolerance, high susceptibility to diseases like Anthracnose and Pythium.
Ecological Information
Introduced/Invasive status in most of North America; provides minimal wildlife value; often considered a major weed in professional turf due to its rapid spread and unsightly seed heads; competes aggressively with desirable species like Kentucky Bluegrass.