Scientific Name: Polygonum persicaria

Common Name: spotted ladysthumb

Other Common Names: pondshore knotweed, smart weed, lady's thumb, lady's thumb smartweed

Synonyms: Persicaria maculata, Persicaria maculosa, Persicaria persicaria, Persicaria ruderalis, Persicaria vulgaris, Polygonum dubium, Polygonum fusiforme, Polygonum minus, Polygonum persicaria var. angustifolium, Polygonum persicaria var. ruderale, Polygonum puritanorum

Habit: This erect summer annual flowers from July to October. It can grow up to 3 1/2 feet in height with numerous branches.

Leaves: The alternately arranged leaves are lance to egg shaped, and grow from 2 to 6 inches long and can be up to 2 inches wide. The leaves have a hairy upper surface, and margins, while the lower surface remains smooth. The leaves often have a purple mark in the center, resembling a lady's thumb.

Identifying Characteristics: A membranous sheath or ocrea surrounds the base of each petiole. This species has stiff hairs arising from the top of each ocrea.

Flower Seed Head: The pink or white flowers are usually grouped in terminal spikes on the ends of long, hairy stems.

Seed Fruit: Each seed is enclosed in an achene. The achenes are a glossy black, and are circular to oval, 2.5 to 3.5 mm wide.

Where Found: This plant prefers moist soil.

  • 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: red

  • Growth habit: upright and nonwoody

  • Stem: round or oval

  • Leaf structure: simple

  • Leaf hairs: has hairs

  • Flower symmetry: radial symmetery

  • Flower diameter: pencil

  • Root structure: taproot; fibrous

  • Leaf stalk: shorter than leaf