An On-line Version of an Aquatic Plant Identification Manual for Washington's Freshwater Plants

How to Use this Website


Freshwater aquatic plants are found in most lakes and rivers in Washington. They range from tiny floating plants that can form mats on a lake surface to reed-like plants that grow two meters above the water. Aquatic plants are an important part of freshwater environments. They provide food and shelter for a wide variety of insects, amphibians, fish, reptiles, mammals, and birds. They also form an important link in nutrient cycles and stabilize shorelines.

The purpose of this website is to help with identifying aquatic plants that are likely to be seen in Washington's waterbodies. Many of the plants described here also can be found in streams, wetlands, drainage ditches, and other freshwater habitats. This website has been designed for people who do not have a scientific background; it should also be useful for professionals who need assistance in identifying aquatic species. Although many of the common aquatic plants are described, this website does not include all the aquatic plants in Washington. Use additional references if you canít identify a plant by using this website.

Plants with similar growth forms and from similar habitat types are grouped together in categories and each category is identified with an icon. If the plant being described is a sensitive, threatened, and endangered species, a non-native invasive aquatic plant, or was used by Native Americans, an appropriate icon will be displayed on the plant description page. The plant categories are:

Go to the category that best seems to describe the unknown plant. Compare the plant with the illustrations and photographs of each plant within the category. When you find a similar looking plant, read the species description to see if your plant fits the description. Refer to the Glossary for definitions of unfamiliar terms. See a sample page and a description of the layout of the page. 

If the plant fits the general description, use a metric ruler to measure leaves, petals, and other plant parts.  Sometimes, the number of leaflets or petals helps with identification. When counting the numbers of leaves, especially those arranged in a whorl around the stem, it is often helpful to examine a cross-section of the plant at a node. Use magnification to see the small details of the plant structure. If the plant doesnít seem to be referenced within a particular category, look at the plants in similar categories. Depending on the time of year, flowers, fruits, or floating leaves may not be present or underwater leaves may have decomposed. A young plant may appear quite different in appearance than a mature plant.  Donít be discouraged if you canít identify the plant to species. Some species, such as the narrow-leaved pondweeds are notoriously difficult to distinguish from each other.

If you canít identify the plant from this website, you may need to consult other plant references; not all freshwater plants from Washington are described here. See the references section for a list of publications about aquatic plants. Check with the Department of Ecology, the local Washington State University Cooperative Extension Service, the local United States Department of Agriculture, the Natural Resources Conservation Service, the State Noxious Weed Control Board, or your local County Noxious Weed Control Board to see if they may have staff who could help identify the plant.

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