Persicaria amphibia
Persicaria amphibia is a species of flowering plant in the knotweed family
Polygonaceae is a family of flowering plants known informally as the "knotweed family" or "smartweed family"— "buckwheat family" in the United States. The name is based on the genus Polygonum and was first used by Antoine Laurent de Jussieu in 1789 in his book, Genera Plantarum. The name refers...

 known by several common names, including water knotweed, water smartweed, and amphibious bistort. It is native to much of North America and Eurasia, but it is known on most continents as an introduced species
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...

 and sometimes a noxious weed. It grows in many types of wet habitat, such as ponds, streams, and marsh
In geography, a marsh, or morass, is a type of wetland that is subject to frequent or continuous flood. Typically the water is shallow and features grasses, rushes, reeds, typhas, sedges, other herbaceous plants, and moss....

es. It is a rhizomatous
In botany and dendrology, a rhizome is a characteristically horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes...

 perennial herb which takes a variety of forms and is quite variable in morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

. It may be an aquatic plant
Aquatic plant
Aquatic plants are plants that have adapted to living in aquatic environments. They are also referred to as hydrophytes or aquatic macrophytes. These plants require special adaptations for living submerged in water, or at the water's surface. Aquatic plants can only grow in water or in soil that is...

, growing submerged or floating in water bodies, it may grow in muddy and wet areas which are periodically inundated, and it may grow in moist spots on land, such as in meadows. Dry-land and fully aquatic plants are sometimes considered different named varieties of the species.

The plant produces a thick stem from its rhizome. The stem may creep, float, or grow erect, rooting at stem nodes that come in contact with moist substrate. Stems are known to reach 3 meters long in aquatic individuals. The stems are ribbed and may be hairless to quite hairy in texture. Leaves are lance-shaped or take various other shapes and are borne on petioles
Petiole (botany)
In botany, the petiole is the stalk attaching the leaf blade to the stem. The petiole usually has the same internal structure as the stem. Outgrowths appearing on each side of the petiole are called stipules. Leaves lacking a petiole are called sessile, or clasping when they partly surround the...

. They may be over 30 centimeters in length. The inflorescence
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...

 is a dense terminal cluster of many five-lobed pink flowers. Plants may have bisexual or unisexual flowers
Plant sexuality
Plant sexuality covers the wide variety of sexual reproduction systems found across the plant kingdom. This article describes morphological aspects of sexual reproduction of plants....

, with some plants bearing only male or only female flowers. The fruit is a shiny brown rounded achene
An achene is a type of simple dry fruit produced by many species of flowering plants. Achenes are monocarpellate and indehiscent...

 around 3 millimeters long.

Various parts of this plant were used by several Native American
Indigenous peoples of the Americas
The indigenous peoples of the Americas are the pre-Columbian inhabitants of North and South America, their descendants and other ethnic groups who are identified with those peoples. Indigenous peoples are known in Canada as Aboriginal peoples, and in the United States as Native Americans...

 groups as medicinal remedies
Herbalism is a traditional medicinal or folk medicine practice based on the use of plants and plant extracts. Herbalism is also known as botanical medicine, medical herbalism, herbal medicine, herbology, herblore, and phytotherapy...

and sometimes as food.

External links

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