Scientific Name: Polygonum pensylvanicum

Common Name: Pennsylvania smartweed

Other Common Names: Pennsylvania knotweed, pinweed

Synonyms: Persicaria bicornis, Persicaria longistyla, Persicaria mississippiensis, Persicaria pensylvanica, Polygonum bicorne, Polygonum longistylum, Polygonum mexicanum, Polygonum mississippiense

Habit: An up-right branched plant reaching heights of 1 to 4 feet with a shallow tap root and fibrous secondary roots. This species spreads by seed germinating in the early to late spring.

Leaves: Usually lance shaped with very short stalks and one prominent vein in the center.

Identifying Characteristics: This species has large nodes where each alternate leaf is attached with a papery sheath surrounding the attachment.

Flower Seed Head: Found in a spike-like terminal cluster, flowers are usually pink to white.

Seed Fruit: Achenes house the shiny, black, flat, tear-shaped seeds measuring 3 mm.

Where Found: Throughout the United States this plant is usually not a factor in turf. However, it plagues landscapes, horticultural, and agronomic crops as well as nurseries.

  • 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: has hairs

  • Flower color: pink

  • Growth habit: upright and nonwoody

  • Stem: round or oval

  • Leaf structure: simple

  • Leaf hairs: has hairs

  • Flower symmetry: radial symetery

  • Flower diameter: dime

  • Root structure: taproot

  • Leaf stalk: shorter than leaf