Polygonum aviculare (Common Knotweed) - photos and description

Patch of many plants


Leaf petioles included in ocreae

General: Slender annuals branching from the base. Foliage is bluish-green, and the plants have a prostrate to ascending growth habit. Often mat-forming. Plants glabrous.

Flowers: The flowers are tiny, petals absent, the sepals greenish to pink with white margins, growing in clusters in leaf axils. We measured a flower at 2.5 mm diameter and 2 mm long.

Leaves: Leaves alternate, narrowly lanceolate to oblong. We measured a leaf at 14 mm long by 5 mm wide. Petioles included in the ocreae, the ocreae translucent and with a ragged margin.

Height: Plant length listed in Budd's Flora to 50 cm long, we measured plants to a spread of 18 cm (and a height of 9.5 cm).

Habitat: Yards, roadsides, waste places.

Abundance: Common.

Origin: Introduced.

Synonym: Listed in some of the field guides we use as Polygonum arenastrum.

How to identify this species of Polygonum: Sprawling to ascending, leaves +- oblong.

Similar species: This plant might be confused with the similar Polygonum achoreum (Striate Knotweed) which blooms at the same time and grows in similar habitat. However that species has mostly ovate leaves.

When and where photographed: Photos taken August 9th and 13th, edge of lawn along a gravel bike path in the city of Regina, SK.