Annual Bluegrass
Poa annua · Cool-season, Annual (can be Perennial in specific climates), C3
Grass Family
Poaceae, Subfamily Pooideae, Tribe Poeae
Grass Category
Invasive/Weed Grass (often found in Lawn/Turf and Golf Course Grass)
Variety / Cultivar
Common (often exists as complex biotypes from annual to short-lived perennial)
Hardiness Zones
USDA Zones 2-10; thrives in cool, moist weather; enters dormancy or dies during extreme heat; high cold tolerance during winter months.
About This Grass
A light green, low-growing grass with a tufted habit. It is highly noticeable due to its prolific, small, whitish-green open panicle seed heads which can appear even at very low mowing heights. It has a soft texture and often stands out in darker turf. It tends to yellow or die back in hot, dry summer conditions.
Blade Characteristics
Fine to medium width (2-3mm), flat or slightly folded, smooth texture. Blade tips are distinctly boat-shaped. Color is a yellowish-green to bright light green. Vernation is folded in the bud; ligule is membranous, long, and pointed; auricles are absent.
Root System
Shallow fibrous root system; very poor drought tolerance. Fast establishment from seed but does not form a strong, deep sod. Tends to produce minimal thatch except in dense mats.
Growing Information
Origin Region
Native to Europe and Eurasia; widely naturalized throughout temperate regions globally
Growth Habit
Bunch-type into low-growing mats; occasionally produces weak stolons; rapid spreader via prolific seeding
Sunlight & Water Needs
Full sun to partial shade; prefers damp, fertile soils. Requires frequent watering to survive; has very low drought tolerance and will go dormant or die in high heat/low moisture.
Mowing & Maintenance
Maintenance is usually focused on suppression. Can survive mowing heights from 0.125 inches (putting greens) to 3 inches. High seed production makes it difficult to control. Low maintenance if left as a weed, but high maintenance if trying to keep alive in summer.
Special Characteristics
Extremely high seed production; can produce seeds while mowed short; poor heat tolerance; low wear tolerance due to shallow roots; high salt tolerance; susceptible to many turf diseases.
Ecological Information
Introduced/Invasive in many regions; provides minor forage for small birds but generally considered a nuisance in managed landscapes; rapid colonizer of bare or over-watered soils; often found in golf greens and athletic fields.