swamp smartweed

Persicaria hydropiperoides, commonly called swamp smartweed, mild waterpepper, false waterpepper, or sometimes simply waterpepper, is a species of flowering plant in the buckwheat family. It has a widespread distribution across much of North America and South America. Its preferred habitat is in moist, saturated to inundated soils growing in full sun to partial shade; such as swamp forests, marshes, streams, shorelines, and ditches. It is sometimes semi-aquatic.

Swamp smartweed is quite variable and is sometimes divided into several varieties, some of which may be better treated as species in their own right.