Horned Pondweed

Zannichellia palustris L. 

 Also known as: pondweed.

Also known as: pondweed.

Horned pondweed has long, linear, thread-like leaves. They are arranged in whorls on slender branching stems. Leaf tips taper to a point. It has tendril-like roots and slender rhizomes. The seeds are horn-shaped and form in the leaf axils.