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Pest Information

Prostrate Knotweed

Prostrate Knotweed

  • Latin Name: Polygonum Arenastrum
  • Common Name: Prostrate Knotweed
  • Other Names: Common knotweed, doorweed, knotgrass, nutgrass, stonegrass, wiregrass, wireweed, knotweed, pinkweed, bird grass, goose grass, waygrass, matgrass

Pest Details

Prostrate Knotweed
Prostrate Knotweed
Prostrate Knotweed


Introduced from Europe. Now found throughout the United States and southern Canada.


Annual, or weak perennial that may survive winters in moderate climates. Seeds germinate from November into spring, and plants become mature from late spring into the early fall. Prostrate knotweed differs from other knotweeds by its very low-growing habit, forming a dense mat on the surface of the soil. In cultivated fields the stems may begin to grow upright, standing even as high as 12 inches.


Stems are tough, slender, and with a zigzag appearance, swollen at the joints and extensively branched. Where stems touch the ground they may form roots at the nodes. Leaves are very small, oval, and bluish green and dull in appearance. Characteristic of the buckwheat family is the sheath around the stem at the base of the leaf. Flowers are tiny, on short stalks in small clusters at the base of the leafstalk. Flowers may be green with pink or white margins.

Characteristicts Important to Control:

A problem weed in any soil environment, thriving in hard, dry soils along roadsides and waste places, as well as in well irrigated landscape and turf situations. The extremely tough roots make it a difficult weed to remove physically. Knotweed can be discouraged from growing if soil compaction is minimized, and if compacted soil is loosened or aerated. Dense turf will restrict its growth.

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