Few plants can root and grow in running water; therefore, most of those that live in rivers and streams are found along the banks or in quiet pools where the environment is similar to that of a lake or pond. Plants with floating leaves do not do well in fast-moving streams because the current pulls the leaves under. But when rooted plants gain a foothold and manage to reproduce, they can grow so numerous that they slow the flow of water and can even cause flooding.

River and stream plants may be classified as submergent, floating aquatic (water), or emergent according to their relationship with the water.

A submergent plant grows beneath the water. Even its leaves lie below the surface. Submergents include the New Zealand pygmyweed, tape grass, and water violet.

Floating aquatics float on the water's surface. Some, such as duckweed, have no roots...