Pondweeds with Large Floating Leaves
Updated: May 14, 2020
These three large-leaved pondweeds have similar surface leaves but can be distinguished from one another based on their submerged leaves.
Big-Leaf Pondweed (Potamogeton amplifolius)
Surface leaves of Big-Leaf Pondweed (SEINet)
Submerged leaves of Big-Leaf Pondweed (Minnesota Wildflowers)
Big-leaf pondweed is also know large-leaved pondweed, broad leaf pondweed or bassweed. It has large, curly underwater leaves that appear to fold in on themselves and arch. They are up to 8 inches long and 2 1/2 inches wide. The submersed leaves have more veins than do those of other pondweed species, up to 49. Floating leaves are elliptical in shape, are up to 4 inches long by 2 inches wide, and are leathery in texture.
Ribbon-Leaf Pondweed (Potamogeton epihydrus)
Floating leaves are firm, green, elliptic, 1 to 3 inches long, up to ¾ inch wide, and rounded to bluntly pointed at the tip.
Submersed leaves are alternate on opposite sides of the stem (2-ranked), bright green to reddish, linear and ribbon-like, 2 to 8 inches long, 3/8 inch wide, bluntly to sharply pointed at the tip, and stalkless. Excerpted from: https://www.minnesotawildflowers.info/aquatic/ribbon-leaf-pondweed.
Floating Pondweed (Potamogeton natans)
Surface Leaves of Floating Pondweed (Photo by Maria Gross)
This is a very common pondweed. Floating leaves are firm, green, oval-elliptic to egg-shaped, 1½ to 4+ inches long, 1 to 2 inches wide, toothless, mostly, pointed to rounded at the tip, with 17 to 37 veins flanking the midrib.
Submersed leaves are sparse and are generally modified to be long and needle-like or ribbon like, 3-8 inches long and less than 1/8 inch wide.
Surface and Submerged Leaves of Floating Pondweed (Wikimedia Commons)