Potamogeton robbinsii

Potamogeton robbinsii, commonly known as Robbins' pondweed, is a North American perennial herb.

It is found in "deep to shallow, quiet, often muddy waters of lakes, ponds, and rivers."

This plant may form dense colonies that carpet the muddy substrates of riverbottoms and lakebeds. It rarely flowers, but when it does it is very easy to identify, as it is the only Potamogeton that has branching inflorescences.