Polygonum paronychia, commonly known as dune knotweed, is a perennial herb native to coastal dune systems and sandy shores of western North America, from British Columbia to California. It thrives in the harsh conditions of coastal environments, including beaches, foredunes, and coastal bluff scrub, where it plays a role in stabilizing sand and contributing to dune formation. This species typically forms low mats or mounds, with prostrate to slightly upright multibranched brown stems that can reach up to 40 inches in length and may root at nodes when in contact with moist substrate.

Dune knotweed is valued for its resilience in coastal garden settings, where it can serve as an effective ground cover, stabilizing sandy soils and tolerating salt spray. Its linear to lance-shaped leaves with rolled edges and bristly midribs are mostly concentrated around the tips of the stem branches, providing a unique texture in the landscape. The small, inconspicuous flowers, which bloom from late spring to early fall, are nestled in the leaf axils and feature five narrow white or pinkish corolla lobes. While not showy, they add a subtle charm to the plant. Dune knotweed requires well-drained sandy soils and full sun exposure to thrive and is relatively low-maintenance, needing minimal supplemental water once established. It is occasionally used medicinally, as poultices made from the plant have been used to treat whitlow infections. Gardeners should be aware that in non-coastal environments, it can become invasive and should be planted with caution.CC BY-SA 4.0