Scientific Name: Polygonum caespitosum

Common Name: Oriental lady's thumb

Other Common Names: bristled knotweed, bunchy knotweed

Synonyms: Persicaria posumbu, Polygonum caespitosum

Habit: This erect, sprawling summer annual grows up to 3 1/2 feet in height. It flowers from mid summer till the first frost in the fall.

Leaves: The alternately arranged leaves are elliptical in shape, although they can be lance-shaped. They are usually 1 to 3 inches in length, and 1/2 to 1 1/4 inches wide. The leaves are occasionally hairy.

Identifying Characteristics: The first true leaves are hairy

Flower Seed Head: The small, dark pink or red flowers occur in spikes at the tips of stems.

Seed Fruit: The seeds develop in a black achene.

Where Found: This plant can be found in moist, disturbed areas

  • Life cycle: summer annual

  • Milky sap: Not Present

  • Plant type: Herb

  • Thorns: Not Present

  • Plant family: Polygonaceae

  • Leaf arrangement: alternate

  • Leaf shape: lance

  • Ochrea: Present

  • Leaf margin: entire

  • Stem hairs: no hairs

  • Flower color: pink; red

  • Growth habit: prostrate and nonwoody

  • Stem: round or oval

  • Leaf structure: simple

  • Leaf hairs: has hairs

  • Flower symmetry: radial symmetery

  • Flower diameter: pencil

  • Root structure: fibrous; taproot

  • Leaf stalk: shorter than leaf; none