Common Knotweed (Note: This is a broadleaf weed, not a true grass)
Polygonum aviculare · Summer Annual Broadleaf; C3 photosynthesis (not a grass/Poaceae)
Grass Family
Polygonaceae (Buckwheat family)
Grass Category
Invasive/Weed Grass mimic (Commonly mistaken for grass in lawns)
Variety / Cultivar
Common wild type
Hardiness Zones
Successfully grows in USDA Zones 3-10; germinates in early spring as soil warms.
About This Grass
A low-growing annual that forms dense, wiry mats. Stems are blue-green and zig-zagged, characterized by swollen nodes (knots) encased in a papery sheath.
Blade Characteristics
Not true grass blades; leaves are elliptical, 0.5-1.5cm long, dull blue-green color, with a papery ocrea (sheath) at the base of each leaf petal.
Root System
Deep, thin taproot that allows it to survive in extremely compacted soils where true grasses fail; non-rhizomatous.
Growing Information
Origin Region
Native to Europe and Eurasia; naturalized throughout North America in compacted soils
Growth Habit
Prostrate, mat-forming; stems emerge from a central taproot and spread horizontally
Sunlight & Water Needs
Full sun to partial shade; highly drought-tolerant; thrives in dry, compacted, or nutrient-poor soils.
Mowing & Maintenance
Extremely low-profile; often survives below mower blade height (0.5 inches); difficult to control mechanically once established.
Special Characteristics
Extreme traffic tolerance; indicator plant for soil compaction; resistant to many common selective grass herbicides.
Ecological Information
Introduced/Invasive in turf; seeds are a food source for songbirds; outcompetes native grasses in high-traffic waste areas.