University of Maryland Extension

Knotweed

prostrate knotweed

Photo: Knotweed, Polygonum avicular

(More lawn weeds)  (Control Options) (General Weed Gallery)
General description: Knotweed is a summer annual broadleaf weeds that spreads by seed. Is low-growing and has wiry stems that form a mat. Leaves vary in shape depending on the maturity of the plant. Juvenile leaves are dark green and are long and slender. Older leaves are smaller and are duller green in color. Leaves are alternate along the stem. Small white or yellow flowers are inconspicuous and are located at the leaf axils. Blooms midsummer through the fall.
Conditions that favor growth: It grows in areas with heavily trafficked, compacted soils.

Cultural control: Maintain healthy, dense turf that can compete and prevent weed establishment.
Mechanical control: Hand pulling or using an appropriate weeding tool are the primary means of mechanical weed control in lawns. This is a viable option at the beginning of an infestation and on young weeds. Hand pulling when the soil is moist makes the task easier. Weeds with tap roots like dandelions or have a basal rosette (leaves clustered close to the ground) like plantain are easier to pull than weeds such as Bermudagrass (wiregrass) or creeping Charlie (ground ivy) that spread with stolons or creeping stems that root along the ground.
General chemical control: Spot treat weeds with a liquid, selective, postemergent, broadleaf weed killer applied when weeds are actively growing. Look for a product with one or more of the following active ingredients: 
2, 4-DMCPP (mecoprop), Dicamba (be careful when using around tree and shrub roots) or Triclopyr. 

Organic control: 

For a glossary of herbicide terms and additional information see: control options     

                                                                                                 

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