Lawn Guardian

How to Get Rid of Prostrate Knotweed

Polygonum aviculare

broadleaf weedUSDA zones 2–10Active: spring, summer

One of the earliest germinating summer annuals. Thrives in compacted, high-traffic areas. Often the first weed to appear along driveways and paths.

How to identify it

Wiry, branching stems lying flat; small blue-green lance-shaped leaves; papery sheaths (ocrea) at leaf nodes; tiny white-pink flowers.

Treatment options

Cultural (prevention): Aerate compacted areas

Knotweed is a compaction indicator. Core aerate high-traffic paths and edges.

When: Aerate in fall; address traffic patterns

Cultural (prevention): Hand pulling

Pull young plants including taproot. Remove before seed set.

When: Pull in spring when plants are young

Organic: Corn gluten meal

Spring pre-emergent that targets knotweed germination.

When: Apply in very early spring — knotweed germinates before most summer annuals

Chemical: Broadleaf herbicide (2,4-D)

Effective on young knotweed plants. Less effective on mature, wiry stems.

When: Apply in spring when plants are young and actively growing

Active ingredient: 2,4-D — e.g. Ortho Weed B Gon

Grass safety: always match herbicides to your grass species — products safe on Kentucky bluegrass can kill St. Augustine or centipede. Lawn Guardian checks this automatically against your lawn profile.

Stop prostrate knotweed at the right moment, automatically

Lawn Guardian turns this guidance into a schedule timed to your USDA zone and this week's actual weather — and adapts every time you log what you've done.

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Related weeds

Sources: Purdue University Turfgrass Science: Use Growing Degree Days to Better Time Your Applications · University of Missouri Extension: Cool-Season Grasses: Lawn Maintenance Calendar · University of Minnesota Extension: Pre-emergent Herbicides for Crabgrass Control in Lawns