Annual Bluegrass
Poa annua · Cool-season, Annual or short-lived Perennial, C3
Grass Family
Poaceae, Subfamily Pooideae, Tribe Poeae
Grass Category
Invasive/Weed Grass, Golf Course Grass (notably on greens), Lawn Weed
Variety / Cultivar
Common (Wild-type); sometimes classified as Poa annua f. reptans (perennial biotype)
Hardiness Zones
USDA Zones 3-11; widely adaptable but thrives in cool, moist transition zones and temperate regions. Suffers significant die-back in high summer heat (above 85°F).
About This Grass
A light green, low-growing grass with a clumping habit that often forms dense mats. It is most distinctive for its prolific production of white, branched seed heads even at very low mowing heights.
Blade Characteristics
Fine to medium width (2-3mm), soft and crinkled when young with a characteristic 'V' shape. Tips are boat-shaped (keeled). Light green to yellowish-green color. Vernation is folded. Ligule is membranous, long, and white. Auricles are absent.
Root System
Shallow fibrous root system; weak heat and drought tolerance. Rapid establishment from seed; low thatch tendency but forms dense clusters that can disrupt turf uniformity.
Growing Information
Origin Region
Europe and Eurasia; naturalized worldwide in temperate climates
Growth Habit
Bunch-type to semi-stoloniferous; low-growing, spreading via tillers and sometimes rooting at nodes
Sunlight & Water Needs
Partial shade to full sun; prefers moist to over-watered conditions. High water requirement to survive summer heat; poor drought tolerance.
Mowing & Maintenance
Highly adaptable; can survive mowing heights from 0.1 inch (greens) to 3 inches. High maintenance as a weed because it requires frequent pre-emergent applications to control; as a turf, it requires high water and fungicide inputs.
Special Characteristics
Extremely prolific seed production (up to 360 seeds per plant); can produce seeds even when mown at 1/8 inch. High shade tolerance; very poor heat and salt tolerance; high susceptibility to diseases like Anthracnose.
Ecological Information
Introduced/Invasive status in most lawns. Provides minimal wildlife value but acts as an opportunistic colonizer of compacted or over-watered soils. Often found in companion with Bentgrass or Kentucky Bluegrass in older turf stands.