Page authors: Don Knoke, David Giblin
Polygonum aviculare
common knotweed

Distribution: Occurring on both sides of the Cascades crest in Washington; Alaska to California, east across North America to the Atlantic Coast.

Habitat: Dry or slightly moist, disturbed soil, often where hard-packed.

Flowers: May-October

Origin: Both native and introduced

Growth Duration: Annual

Conservation Status: Not of concern

Pollination: Bees, flies


Highly variable species, prostrate and spreading (but not rooting at the nodes) to occasionally erect, freely-branched annual, the stems terete, striate, up to 1 m. long.


Numerous, bluish-green, only slightly reduced upward, narrowly oblong, 1-3 cm. long and 2-6 mm. broad, narrowed to a very short, jointed petiole; stipules lacerate, 3-6 mm. long.


1-3 in the axils of the leaves or leaf-like bracts, the pedicles 1-3 mm. long, erect; perianth 2.5 mm. long, divided 2/3 the length, the segments 5, oblong, sub-equal, greenish with white to pink or red margins.


Achene with 3 sharp angles, brownish, smooth.

Accepted Name:
Polygonum aviculare L.
Publication: Sp. Pl. 1: 362. 1753.

Synonyms & Misapplications:
(none provided)
Additional Resources:

PNW Herbaria: Specimen records of Polygonum aviculare in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Polygonum aviculare checklist entry.

OregonFlora: Polygonum aviculare information.

E-Flora BC: Polygonum aviculare atlas page.

CalPhotos: Polygonum aviculare photos.

USDA Plants: Polygonum aviculare information.

66 photographs:
Group by