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Prostrate knotweed

Prostrate knotweed

Polygonum aviculare

Identify the Prostrate knotweed from a photo and log your finds with Florapass.

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How common: Common

Alien species

Prostrate knotweed is a tough, low annual that makes flat mats on hard‑trodden ground. You see it on paths, yards, field edges and roadsides, often in towns and farmyards. The tiny green‑white to pink flowers sit where the leaves meet the stems. It is widespread across temperate regions.

Did you know?

  • It endures heavy foot traffic and even mowing, which is why it thrives in paths and yards.
  • Its flowers are mostly self‑pollinating.

About the species

Identification

Low, mat-forming annual with many wiry, jointed stems that sprawl along the ground or partly rise. Stems often much branched. Leaves small, narrow oval to reverse-oval, plain green to gray‑green, with a thin, silvery papery sleeve around the stem at each leaf base that soon splits into threads. Tiny greenish flowers with white or pink edges are in small clusters where leaves meet the stem. Later they form small, three‑sided hard seeds, often tucked inside the old flower parts. Differs from taller smartweeds by its flat, lawn‑hugging stems and the fraying papery sleeves. Flowers in Finland from June to September.

Plant group

Herbaceous plants

Habitat

yards and roadsides, shore

Flowering

Jun–Sep

About the habitat

Bare, compacted or disturbed ground such as paths and yards, waste places, field edges, shorelines and roadsides. Prefers open, sunny sites and tolerates trampling. Common across most of Finland; rare in northern Lapland.

Sources

Photo: David Anderson, CC BY 4.0 https://www.gbif.org/occurrence/5938074271

Text: Pinkka: Verso- ja leviäintunnistus - Kaikki versot, CC BY 4.0 https://laji.fi/taxon/MX.38217

Text: Pinkka: IPS-153 Flora of Subarctic Europe - Nardus-Pyrola, CC BY 4.0 https://laji.fi/taxon/MX.38217

Text: Pinkka: Maatalouslajintuntemus - Caryophyllaceae, Amaranthaceae, Polygonaceae, Violaceae, Cucurbitaceae, Begoniaceae, CC BY 4.0 https://laji.fi/taxon/MX.38217

Text: Pinkka: Verso- ja leviäintunnistus - Kaikki leviäimet, CC BY 4.0 https://laji.fi/taxon/MX.38217

Text: Wikipedia (Finnish), CC BY-SA 4.0 https://fi.wikipedia.org/wiki/Pihatatar

See also