Annual Bluegrass
Poa annua · Cool-season, Winter Annual (sometimes short-lived perennial), C3
Grass Family
Poaceae, Subfamily Pooideae, Tribe Poeae
Grass Category
Invasive/Weed Grass, Golf Course Grass (when maintained as greens), Lawn Weed
Variety / Cultivar
Common Poa annua (var. annua)
Hardiness Zones
USDA Zones 3-11; survives cold winters as seeds; dies in heat or goes dormant in Zone 7 and above during summer.
About This Grass
A light green, low-growing grass with a tufted habit. It is known for prolific seed production even at very low mowing heights. It often turns yellowish or dies off during summer heat.
Blade Characteristics
Blade width: 2-4mm (medium); Shape: Flat or slightly folded; Tip: Distinctive boat-shaped tip; Color: Light yellow-green; Vernation: Folded; Ligule: Membranous, silvery/white, about 1-3mm; Auricles: Absent.
Root System
Shallow, fibrous root system; lacks rhizomes or true stolons but can root from nodes; very low drought tolerance due to shallow depth; high thatch potential.
Growing Information
Origin Region
Native to Europe and Asia; cosmopolitan distribution worldwide in temperate climates
Growth Habit
Bunch-type/Clumping, though it can root at lower nodes and form low, spreading mats
Sunlight & Water Needs
Partial to Full Sun; prefers moist to wet conditions; poor drought tolerance; thrives in compacted, damp soils with high nitrogen.
Mowing & Maintenance
Hard to control; survives mowing heights from 0.1 inch (greens) to 3 inches; requires high maintenance to eradicate or high moisture/fertility to maintain as turf.
Special Characteristics
Extremely high seed production; shade tolerant; highly resistant to low mowing; poor heat/drought tolerance; often becomes unsightly when it produces white seed heads in spring.
Ecological Information
Introduced/Invasive in most regions; provides some food for small birds but generally considered a nuisance weed that outcompetes desired turf grasses in spring.