polygona

Polygona is a genus of flowering plants in the family Polygonaceae, commonly known as the knotweed family. The genus includes several species, many of which are native to Europe and Asia. Polygona species are typically herbaceous perennial plants, though some can be shrubs. They are characterized by their jointed stems, which often give rise to the common name "knotweed." The leaves are usually simple and alternate, with a distinctive membranous sheath called an ocrea at the base of the petiole.

The flowers of Polygona are small and inconspicuous, often greenish or reddish, and are borne in dense spikes or panicles. The fruits are small, three-sided achenes, which are enclosed within the persistent, often winged, tepals. Many Polygona species are known for their vigorous growth and ability to spread rapidly, making some of them considered invasive in certain regions outside their native range.

One well-known species is Polygonum aviculare, or knotgrass, which is a widespread weed found in disturbed areas, fields, and paths. Other species, like Polygonum cuspidatum (Japanese knotweed), are notorious for their invasive potential, forming dense thickets that can outcompete native vegetation. Despite their invasive tendencies, some Polygona species have traditional medicinal uses. The genus is closely related to other members of the Polygonaceae family, such as Rumex (dock) and Rheum (rhubarb).