Annual Bluegrass
Poa annua · Cool-season, Winter Annual, C3
Grass Family
Poaceae, subfamily Pooideae, tribe Poeae
Grass Category
Invasive/Weed Grass, Lawn/Turf Weed
Variety / Cultivar
Common (Wild Type)
Hardiness Zones
USDA Zones 3-11 (occurs as an annual in most, though some perennial subspecies exist)
About This Grass
A clumping, bright-green, low-growing grass reaching 2-8 inches if unmowed. It is highly noticeable due to its prolific whitish seed heads and light-green color contrasting with darker turf grasses. It thrives in compacted, moist soil.
Blade Characteristics
Fine to medium width (2-3mm), soft and crinkled/transverse wavy appearance. Leaf tips are boat-shaped (typical of Poa genus). Ligule is long, membranous, and white. Vernation is folded. No auricles.
Root System
Shallow, fibrous root system. High thatch-forming tendency in dense patches. Fast establishment but lacks drought and heat tolerance.
Growing Information
Origin Region
Eurasia, now naturalized globally in temperate climates and high-elevation tropics
Growth Habit
Bunch-type or semi-prostrate, occasionally produces short runners or adventitious roots at nodes
Sunlight & Water Needs
Partial to Full Sun; requires frequent moisture and high humidity. Highly sensitive to drought and heat, often dying back in summer.
Mowing & Maintenance
Mowing height range from 0.125 to 2.5 inches. High maintenance as a turf weed; requires frequent pre-emergent herbicide application and aeration. High nitrogen levels encourage its spread.
Special Characteristics
Extreme seed production (prolific), can set seed even at very low mowing heights. Poor heat and salt tolerance. High wear tolerance in cool weather but dies in heat leaving bare spots.
Ecological Information
Introduced/Invasive status in lawns and golf courses. Provides minimal wildlife value; primarily considered a nuisance weed that outcompetes desired turf in early spring and fall.