Illinois pondweed is a perennial plant that has mostly submerged leaves, sometimes with a few floating leaves in an alternate pattern. The submerged leaves are blade-like 1 to over 7 inches long and 1/2 to 2 1/2 inches wide. The petiole is short on submerged leaves and less that the leaf in length. Floating leaves are often not present. Floating leaves are blade-like to elliptical 1 to 6 inches long and 3 to 2 inches wide. Fruits are greenish 1/2 to 3 inches long and 1/8 to1/4 inches wide, located on the tip of stems and usually stick above the water surface.
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. Illinois pondweed is utilized as food by ducks and some other types of wildlife.