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 (putting greens), Sports Turf
Variety / Cultivar
Common (Poa annua f. annua)
Hardiness Zones
USDA Zones 3-10. Highly cold tolerant but suffers extreme heat stress and summer die-back in warm climates.
About This Grass
A light green, low-growing grass with a prolific seed-producing habit. It typically reaches 1-12 inches if left unmowed. It is known for its lime-green color and pale, branched seed heads that emerge even at extremely low mowing heights.
Blade Characteristics
Fine to medium width (2-3mm), soft and thin. Blades are typically light green with a boat-shaped tip, which is a hallmark of the Poa genus. Vernation is folded in the bud; ligule is thin, white, and membranous (1-3mm long). Auricles are absent.
Root System
Vary shallow fibrous root system. High thatch-forming tendency in dense patches. Very fast establishment from seed but poor drought tolerance due to shallow roots.
Growing Information
Origin Region
Native to Europe and Eurasia; now naturalized globally in temperate climates.
Growth Habit
Bunch-type to semi-prostrate; exhibits low, spreading growth and can form small mats via weak tillering.
Sunlight & Water Needs
Prefers partial shade to full sun; requires high moisture and frequent watering. Thrives in compacted, wet, and over-irrigated soils. Low drought tolerance.
Mowing & Maintenance
Maintenance level is high if managed as turf. Mowing height: 0.1 inch (greens) to 2.5 inches. Prolific seeding makes it difficult to control. Requires high nitrogen and frequent fungicide applications in summer.
Special Characteristics
Excellent shade tolerance and tolerance for low mowing. Highly susceptible to heat, drought, and various diseases like Anthracnose and Summer Patch. Extremely prolific seed producer.
Ecological Information
Introduced/Invasive status in many regions. Provides minimal wildlife value; often outcompetes desired turfgrasses in wet/shaded areas. Frequently found in golf course greens and athletic fields.