Annual Bluegrass
Poa annua · Cool-season, Annual or short-lived Perennial, C3
Grass Family
Poaceae, Subfamily Pooideae, Tribe Poeae
Grass Category
Invasive/Weed Grass, though sometimes managed as Turf on Golf Course Putting Greens
Variety / Cultivar
Common Poa annua; multiple ecotypes exist from upright annuals to low-growing reptans types
Hardiness Zones
USDA Zones 3-10; survives cold winters via seeds; dies back in high heat (Transition Zone summer stress).
About This Grass
A light-green, low-growing grass with a clumping habit that often looks 'splotchy' in manicured lawns. It is most notorious for its prolific whitish seed heads that appear even under low mowing heights, creating a speckled, uneven appearance.
Blade Characteristics
Fine to medium width (2-3mm), soft texture, light yellow-green color. Blades are V-shaped or flat with a characteristic boat-shaped tip. Vernation is folded. Ligule is long, white, and membranous; auricles are absent.
Root System
Extremely shallow fibrous root system. High thatch-forming tendency in dense patches. Very fast establishment from seed, but prone to death during heat or drought due to poor root depth.
Growing Information
Origin Region
Native to Europe and Asia; cosmopolitan and naturalized worldwide in temperate climates
Growth Habit
Bunch-type to semi-stoloniferous; rapid spreader through prolific seed production and low-growing tillers
Sunlight & Water Needs
Full sun to heavy shade; thrives in moist to over-watered soils. Requires frequent irrigation due to shallow roots. Poor drought tolerance; will often brown out and die in mid-summer heat.
Mowing & Maintenance
Mowing height 0.1 inch to 2 inches; frequent mowing does not stop seeding. Requires high maintenance to remove from lawns including pre-emergent herbicides and careful water management.
Special Characteristics
Highly invasive in turf; prolific seeder; excellent shade tolerance; very poor heat and drought tolerance; high susceptibility to Dollar Spot and Anthracnose.
Ecological Information
Introduced/Invasive status in most of North America. Limited wildlife value as seeds are small. Often acts as a pioneer species in compacted or disturbed soils.