Water smartweed (Persicaria amphibia) is a species of flowering plant in the knotweed family known by several common names, including longroot smartweed, water knotweed and amphibious bistort.
It is native to most of North America, Asia, Europe, and parts of Africa, and it grows elsewhere as an introduced species.
The stems are ribbed and may be hairless to quite hairy in texture.
Leaves are mostly lance-shaped and are borne on small stalks called petioles. They may be over 30 centimeters in length. The inflorescence is a dense terminal cluster of many five-lobed pink flowers.
It grows in many types of wet habitat, such as ponds, streams, and marshes. It is a rhizomatous perennial herb which takes a variety of forms. It may be an aquatic plant, 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.
The plant can be used herbal medicine (check with a medical professional and do your own research) in the following ways:
- Infusion made with leaves and stems are used for treating stomach pains or diarrhea in children.
- Roots are consumed raw or infusion made with dried roots is used for treating chest colds.
- Apply the poultice of fresh roots to the mouth for treating blisters.
The leaves and roots can also be eaten as food when cooked (do your own research check before consuming).