Smartweeds and Knotweeds
similar plants in the Polygonaceae, all formerly in the genus Polygonum. Check to see if ocreae (leaf stem sheathes) are fringed or unfringed.
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​Japanese knotweed - (Reynoutria japonica)
Bulky, hollow, spotted stems grow to ten feet; leaves are oval-triangular. Introduced and weedy.

Dotted smartweed - (Persicaria punctata)
A common plant of wet soils. Highly variable, erect or decumbent; flowers usually greenish white, sometimes pink. Ocreae fringed.

Arrow-leaved tearthumb - Polygonum sagittatum
White flowers, tiny hooked stem bristles, unfringed ocreae, clasping leaves.

Virginia knotweed - Polygonum virginianum
Greenish white flowers are spaced out along the upper stem; unfringed​ ocreae; leaves are long and broad.

​Pale smartweed - Persicaria lapathifolia
Standing to six feet, with drooping greenish-white​ flower clusters. Unfringed ocreae.

​Lady's Thumb - Persicaria maculosa
Plants are erect or prostrate, pink flowers are tightly packed, unfringed ocreae. Leaves often have a dark, triangular smudge.

Long-bristled smartweed - Persicaria cespitosa
Abundant and weedy, pink flowers, markedly fringed​ ocreae.

Pennsylvania smartweed - Persicaria pensylvanica
Large plants, red stems, unfringed ocreae, crowded pink​ flowers. Wet soils and wetlands.

​False water-pepper - Polygonum hydropiperoides
Pink flowers, fringed ocreae, leaves taste peppery. Prefers wet soils.