Plants have strong ties to the ground they grow from, and they also have a need for water just like anything else. They play a role in filtering rainwater as it reenters the soil and makes its way to the aquifer below. Wetland plants can often let us know when there are changes in the soil and water chemistry. For example, the invasion of Phragmites australis, or common reed, can indicate contamination from high nutrient loading, such as a leaky septic system or excess lawn fertilizer. When the contaminants reach a nearby waterway, algae will proliferate in the water and use up the oxygen supply for other plants and animals. Other invasive species such as purple loostrife can also be problematic.

Native plants can also play an important part in the protection of wildlife. Not only do they provide food, but also shelter and shade. Aquatic animals that live in cool streams rely on the constant shade to stabilize the temperature; cold water holds more oxygen.
A good way to help keep your local waterway healthy is to provide a buffer of native vegetation along its banks. By leaving the natural surroundings intact, runoff water gets filtered, animals have a place to live, and the scenery is often improved.

The Connecticut River Joint Commission has created some informative fact sheets about river buffers. Especially useful is a document titled Planting Riparian Buffers that explains how to turn a bare riverbank into a buffer that works for clean water, stable banks, fish habitat, birds, and wildlife. It includes information on how to establish a riparian buffer: plant selection, sources of material, economically valuable plants, plants for problem visitors such as deer and beaver; invasives to avoid.