Prostrate Knotweed
Polygonum aviculare · Summer Annual, Broadleaf Dicot, C4-like photosynthetic traits
Grass Family
Polygonaceae (Knotweed Family); Not a true grass (Poaceae)
Grass Category
Invasive/Weed Grass (Turfgrass mimic)
Variety / Cultivar
Not applicable (Wild-type species)
Hardiness Zones
USDA Zones 3-10. Germinates when soil temperatures are low (late winter/early spring) and dies back after the first hard frost.
About This Grass
A low-growing, mat-forming annual weed often mistaken for grass from a distance. It features blue-green foliage with small, inconspicuous white-to-pink flowers at the leaf axils. It emerges very early in spring, often appearing as a dense green carpet on bare, compacted soil.
Blade Characteristics
Leaves are alternate, elliptical to linear-oblong, 0.5-3 cm long. They are not true grass blades. The plant features an ocrea (a thin, papery sheath at the base of the leaf) which is a diagnostic feature of the Polygonaceae family.
Root System
Deep, thin taproot that can penetrate heavily compacted soils where true grasses fail to thrive. Rapid establishment in early spring from seed.
Growing Information
Origin Region
Native to Eurasia and North America; widely naturalized globally in temperate and subtropical climates
Growth Habit
Prostrate, mat-forming habit with a central taproot. It spreads radially and is highly resistant to soil compaction.
Sunlight & Water Needs
Full sun preferred; highly drought-tolerant once established. Prefers nutrient-rich, moist, but heavily compacted silty or clay soils.
Mowing & Maintenance
Maintenance involves removal rather than care. It survives extremely low mowing heights due to its prostrate nature. Control requires broadleaf herbicides containing 2,4-D, dicamba, or MCPP, as grass fertilizers do not affect it.
Special Characteristics
Extreme tolerance for soil compaction and foot traffic. It often serves as a bio-indicator of poor soil aeration and high traffic in lawns and sports fields.
Ecological Information
Introduced/Naturalized weed. Seeds are a significant food source for songbirds and upland game birds. In landscapes, it is considered a competitive weed that outpaces turfgrass in stressed areas.