Smartweed, Water Pepper

Polygonum hydropiperoides


Smartweed is a perennial plant that forms dense colonies in shallow water or moist soils and can grow to 3 feet tall. Stems are jointed or have swollen leaf nodes that are surrounded by a tubular sheath. Roots can develop from the leaf nodes. Leaves are alternate, lance-shaped up to 4 inches long but usually less than 1/2 inch wide. Flowers are on spikes at the end of stems (often numerous spikes on the same plant). Flowers begin as greenish then turn whitish or light pink in color as they mature. Fruits are flat, triangular (1/8 inch), dark brown to black.

Submerged portions of all aquatic plants provide habitats for many micro and macro invertebrates. These invertebrates in turn are used as food by fish and other wildlife species (e.g. amphibians, reptiles, ducks, etc). After aquatic plants die, their decomposition by bacteria and fungi provides food (called “detritus”) for many aquatic invertebrates. Smartweed seeds are heavily consumed by ducks, small birds, and small mammals.