Annual Bluegrass
Poa annua · Cool-season, Annual (though some biotypes act as short-lived perennials), C3
Grass Family
Poaceae, Subfamily Pooideae, Tribe Poeae
Grass Category
Invasive/Weed Grass (commonly found in Lawns, Sports Turf, and Golf Courses)
Variety / Cultivar
Common Poa annua (wild-type); includes both Poa annua var. annua (annual) and Poa annua var. reptans (perennial biotypes common on golf greens)
Hardiness Zones
USDA Zones 3-11; survives cold well but lacks heat tolerance; typically dies back or becomes dormant and unsightly during hot summer months.
About This Grass
A light green, low-growing grass characterized by its prolific seed production. It often appears as lighter patches in darker turf and enters senescence/turns yellowish during summer heat. Its most distinct feature is the whitish, branched panicle seed head.
Blade Characteristics
Blade width: 2-4mm (fine to medium); Tip shape: Boat-shaped (keeled); Color: Light yellowish-green; Vernation: Folded; Ligule: Membranous, white, and slightly pointed; Auricles: Absent; Texture: Soft and wrinkled (cross-striated) near the base.
Root System
Shallow, fibrous root system; high thatch-forming tendency in dense patches; fast establishment from seed; very poor drought tolerance due to shallow roots.
Growing Information
Origin Region
Native to Europe and Asia; cosmopolitan and naturalized globally in temperate climates
Growth Habit
Low-growing, bunch-type to slightly stoloniferous; can form dense mats and produces seed prolifically even at very low mowing heights
Sunlight & Water Needs
Partial sun to shade (thrives in moist, shady areas); requires high and frequent watering; prefers fertile, well-irrigated soils with high nitrogen; sensitive to heat stress.
Mowing & Maintenance
Ideal height: 0.1 inch to 2 inches; survives extremely low mowing; requires high maintenance to control; fertilization: thrives on high nitrogen (3-5 lbs N/1000 sq ft); often requires pre-emergent herbicides for control.
Special Characteristics
Prolific seeder; high shade tolerance; poor wear tolerance; very high salt tolerance; highly invasive in managed turfgrass due to its ability to produce seeds while mowed low.
Ecological Information
Introduced/Invasive species in North America; provides some food for small birds but generally considered a nuisance in high-quality turf; colonizes disturbed or over-watered soils effectively.