water hyacinth: a tropical, floating, aquatic plant having spikes of large blue flowers; troublesome in clogging waterways especially in the southern United States.
watershed: a geographic area that drains into a single river system and its tributaries.
weevil: any of several families of mostly small beetles that feed on plants and plant products.
West Nile virus: an animal virus belonging to the family Flaviviridae that causes West Nile encephalitis (inflammation of the brain) and is transmitted by mosquitoes.
wetland: an area that, at least periodically, has waterlogged soils or is covered with a relatively shallow layer of water. Bogs, freshwater and saltwater marshes and freshwater and saltwater swamps are examples of wetlands.