Smartweed (commonly treated as a weed in turfgrass, mixed with various grasses)
Polygonum persicaria · Warm-season/Cool-season adaptable broadleaf annual weed
Grass Family
Polygonaceae (Note: Smartweed is a broadleaf weed, not a true grass belonging to Poaceae, though found mixed with turfgrasses)
Grass Category
Invasive/Weed Grass & Broadleaf Weed
Variety / Cultivar
Wild type
Hardiness Zones
USDA Hardiness Zones 3 through 9
About This Grass
An annual broadleaf weed often infesting lawns and damp areas, featuring distinct pink to purplish spike-like flowers, swollen stem nodes, and lance-shaped leaves often with a dark blotch. Reaches heights of 1 to 2 feet when unmoved.
Blade Characteristics
Leaves are alternate, lance-shaped, entire margins, medium to dark green, often marked with a dark triangular or crescent-shaped spot. Features a membranous sheath (ocrea) around the stem at each node.
Root System
Fibrous root system with a shallow to moderate depth, spreading rapidly in damp or compacted soils, establishing easily from seed.
Growing Information
Origin Region
Europe and Asia, now widely naturalized throughout North America and globally in temperate and subtropical regions
Growth Habit
Stoloniferous and upright branching annual weed that forms dense patches
Sunlight & Water Needs
Thrives in full sun to partial shade; prefers moist to wet soils and poorly drained areas. Moderate drought tolerance once established.
Mowing & Maintenance
Responds poorly to frequent close mowing but can persist at low heights as a prostrate plant. Controlled primarily through selective broadleaf herbicides and improving soil drainage.
Special Characteristics
Low wear tolerance compared to turfgrasses, highly invasive in wet turf areas, difficult to control due to prolific seed production, excellent indicator of wet or compacted soil conditions.
Ecological Information
Introduced species in North America, provides minor food source for wildlife and waterfowl, but considered an aggressive weed in managed turf and agricultural settings.