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Ministry of Agriculture, Food and Rural Affairs


Scientific Name: Prostrate knotweed, Polygonum aviculare L., 

Other Names: renouée des oiseaux, Doorweed, Knot-grass, Mat-grass, Road-spread, traînasse, renouée aviculaire 

Family: Buckwheat or Smartweed Family (Polygonaceae

General Description: Annual, reproducing only by seed.

Habitat: Prostrate knotweed occurs throughout Ontario in areas of moderately heavy foot- or wheel-traffic where the soils may be low in fertility and so heavily compacted that other plants are unable to survive.

Stems & Roots

  • Stems prostrate or semi-erect from a deeply penetrating taproot
  • Stems slender, tough and wiry.
  • In partly shaded situations, such as a grain crop, stems are nearly erect to 30 or 40cm (12-16in.) high.
  • Stem nodes (joints) distinct, thickened, and surrounded by a thin, papery ocrea (membranous sheath) that usually has a torn or jagged margin.


  • Leaves alternate (1 per node), up to 5cm (2in.) long.
  • Width about 1/3-1/5 of their length, usually broadest near or past the middle, and narrower towards both ends. 

Flowers & Fruit

  • Flowers small and inconspicuous, 2mm (1/12in.) or less long, without petals but with 5 tiny greenish, pinkish or purplish sepals, produced in axils of leaves and partially enclosed in the ocrea.
  • Mature "seed" more or less enclosed by the drying sepals, slightly rough, dull brown, triangular in cross-section and about 2mm (1/12in.) long.
  • Flowers from June to September.

Often Confused With/Distinguishing Characteristics
It is distinguished by its thin, wiry stems with small leaves, the ragged ocrea surrounding the stem above every leaf, and its tiny greenish to pinkish or purplish flowers in axils of leaves. Prostrate knotweed, an introduction from Eurasia, is similar to several, closely related, native species of knotweed. One of the more common of these is Striate knotweed, Polygonum achoreum. This plant sometimes occurs in similar situations, especially roadsides, and is distinguished from Prostrate knotweed by its coarser, more erect stems, broader and more rounded leaves, and by its triangular seeds being smooth and olive-coloured.


Prostrate knotweed seedling Prostrate knotweed flower Prostrate knotweed flower bud Prostrate knotweed plant
Click to enlarge.