Annual Bluegrass
Poa annua · Cool-season, typically Annual (though perennial biotypes exist), C3
Grass Family
Poaceae, subfamily Pooideae, tribe Poeae
Grass Category
Invasive/Weed Grass, though sometimes managed on premium Golf Course Greens
Variety / Cultivar
Common Poa annua; no specific ornamental cultivar, often considered a weed
Hardiness Zones
USDA Zones 3-10; survives cold winters but often dies out during heat of mid-summer (summer slump).
About This Grass
A low-growing, light green grass that often appears as bright yellowish-green clumps in darker lawns. It is most distinguishable by its prolific, small, whitish branched seed heads that appear even under low mowing heights.
Blade Characteristics
Fine to medium width (2-3mm), soft and thin; boat-shaped tips; light green to yellowish-green color; folded vernation; long, silvery-white membranous ligule; no auricles.
Root System
Shallow, fibrous root system; lacks rhizomes and stolons; very rapid establishment from seed; poor drought tolerance due to shallow depth.
Growing Information
Origin Region
Native to Europe and Asia; naturalized worldwide in temperate climates
Growth Habit
Bunch-type/clump-forming with a low, spreading prostrate growth habit; can form dense mats
Sunlight & Water Needs
Prefers partial to full sun but is highly shade tolerant; requires frequent moisture and thrives in compacted, over-watered soils; prefers neutral to slightly acidic pH.
Mowing & Maintenance
Extremely low mowing tolerance (can survive at 0.1 inch on golf greens); requires frequent mowing to remove seed heads; high maintenance as a weed due to chemical resistance; thrives with high nitrogen.
Special Characteristics
Prolific seeder; high shade tolerance; salt tolerant; very poor heat and drought tolerance; highly invasive in manicured turf such as Kentucky Bluegrass or Bentgrass.
Ecological Information
Introduced/Invasive status in North America; provides minimal wildlife value; often colonizes disturbed or compacted areas; outcompetes desired turf in wet, shady conditions.