Polygonum is a genus of about 130 species of flowering plant in the buckwheat and knotweed family Polygonaceae. Common names include knotweed and knotgrass. In the Middle English glossary of herbs Alphita, it was known as ars-smerte. There have been various opinions about how broadly the genus should be defined. For example, buckwheat has sometimes been included in the genus as Polygonum fagopyrum. Former genera such as Polygonella have been subsumed into Polygonum; other genera have been split off.
Polygonum arenastrum, commonly known as equal-leaved knotgrass, is a summer annual flowering plant in the knotweed family Polygonaceae. Other common names include common knotweed, prostrate knotweed, mat grass, oval-leaf knotweed, stone grass, wiregrass, and door weed, as well as many others. It is native to Europe and can be found on other continents as an introduced species and a common noxious weed. Knotweed was first seen in North America in 1809 and is now seen across much of the United States and Canada.
Polygonum aviculare or common knotgrass is a plant related to buckwheat and dock. It is also called prostrate knotweed, birdweed, pigweed and lowgrass. It is an annual found in fields and wasteland, with white flowers from June to October. It is widespread across many countries in temperate regions, apparently native to Eurasia and North America, naturalized in temperate parts of the Southern Hemisphere.
Polygonum bidwelliae is an uncommon species of flowering plant in the knotweed family known by the common name Bidwell's knotweed. The plant was named for American suffragist Annie Bidwell, who at one time lived in the Bidwell Mansion in Chico, California. She is the person who collected the type specimen in Northern California.
Polygonum bolanderi is an uncommon California species of flowering plant in the buckwheat family known by the common name Bolander's knotweed.
Polygonum californicum is a species of flowering plant in the buckwheat family known by the common name California knotweed. It is native to the west coast of the United States from Washington, Oregon, and northern and central California in the Coast Ranges and Sierra Nevada foothills as far south as Napa and Tulare Counties. It can be found in many types of open habitats.
Polygonum douglasii is a species of flowering plant in the knotweed family known by the common name Douglas's knotweed. It is native to much of northern and western North America, where it can be found in many types of habitat, including disturbed areas. It has been found in Canada from British Columbia north to Yukon and east as far as Québec, and in the United States as far south as California, New Mexico, Iowa, and New York.
Polygonum minimum is a species of flowering plant in the knotweed family known by the common name broadleaf knotweed. It is native to much of western North America where it can be found in mountainous regions. It grows in the subalpine and alpine climates of high mountain ranges from Alaska to Arizona and New Mexico.
Polygonum paronychia is a species of flowering plant in the knotweed family known by the common names dune knotweed, black knotweed, and beach knotweed. It is native to the coastline of western North America from British Columbia to California, where it grows in sandy coastal habitat such as beaches, dunes, and scrub.
Polygonum polygaloides is a North American species of flowering plants in the buckwheat family known by the common names milkwort knotweed and polygala knotweed. It is native to much of western North America, where it can be found in many types of moist habitat. It is a variable species, usually divided into a number of subspecies.
Polygonum shastense is a species of flowering plant in the knotweed family known by the common name Shasta knotweed. It is native to sections of southwestern Oregon, northwestern Nevada, and northern and central California, where it grows in rocky and gravelly mountainous habitat up to 3300 meters (11,000 feet) elevation. It is most common in the Sierra Nevada. The species name refers to its occurrence on Mount Shasta in Shasta County, California.
Bistorta bistortoides is a perennial herb in the buckwheat and knotweed family Polygonaceae. The species name remains unresolved.
Polygonum heterosepalum, common name dwarf desert knotweed or oddsepal knotweed, is a plant species native to the Great Basin Desert in southwestern Idaho, northern Nevada, northeastern California, and southwestern Oregon. It has been reported from 1 county in California (Modoc), 4 in Nevada, 4 in Idaho, and 5 in Oregon. The species occurs in dry, open sites in sagebrush plains and pine woodlands.
Koenigia davisiae is a flowering plant in the knotweed family that is known by the common names Davis' knotweed or Newberry knotweed.
Koenigia phytolaccifolia is a species of flowering plant in the knotweed family, known by the common name poke knotweed.
Polygonum achoreum, common names Blake's knotweed, leathery knotweed or striate knotweed, is a North American species of plants in the buckwheat family. It is widespread across much of Canada and the northern United States.
Polygonum argyrocoleon, common names silver-sheath knotweed and Persian knotweed, is an Asian species of plants in the buckwheat family. It is native to Siberia, western China, Central Asia, and the Middle East. It has also become naturalized in parts of the United States, primarily the Southwest, and northwestern Mexico.
Polygonum nuttallii is a North American species of flowering plant in the buckwheat family known by the common name Nuttall's knotweed. It grows in the Pacific Northwest, in British Columbia, Washington, and Oregon.
Polygonum spergulariiforme is a North American species of flowering plants in the buckwheat family known by the common name spurry knotweed or fall knotweed. It grows in western Canada and the western United States.
Polygonum tenue, the slender knotweed or pleat-leaf knotweed, is a North American species of plants in the buckwheat family. it is widespread across south-central Canada (Ontario) and the eastern and central United States from Maine to Georgia, west as far as Minnesota, South Dakota, Nebraska, and Texas.
