Elodea nuttallii is a species of waterweed

Elodea

Elodea is a genus of aquatic plants often called the waterweeds. Elodea is native to North America and is also widely used as aquarium vegetation. The introduction of some species of Elodea into waterways in parts of Europe, Australia, Africa, Asia, and New Zealand has created a significant problem...

 known by the common name western waterweed. This is a perennial aquatic plant

Aquatic plant

Aquatic plants are plants that have adapted to living in aquatic environments. They are also referred to as hydrophytes or aquatic macrophytes. These plants require special adaptations for living submerged in water, or at the water's surface. Aquatic plants can only grow in water or in soil that is...

 which is native to North America where it grows submersed in lakes, rivers, and other shallow water bodies. It is also found in Eurasia, where it is commonly weedy; it is not known as a weed species in its native range. It is sometimes used as an aquarium

Aquarium

An aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants...

 plant.

Description

It is similar to its relative, Elodea canadensis. However the leaves taper to an acute point.

It has a thin branching stem with whorls of flat leaves at intervals. Some leaves are recurved and twisted, with minute teeth.

It bears tiny flowers, the staminate

Stamen

The stamen is the pollen producing reproductive organ of a flower...

 ones abscissing

Abscission

Abscission is a term used in several areas of biology. In plant sciences it most commonly refers to the process by which a plant drops one or more of its parts, such as a leaf, fruit, flower or seed...

from their stalks and floating away from the plant. It flowers from May until October.