Willow Slough is the name for the sampling route of my Fourth of July Butterfly Count (program run by the North American Butterfly Association). It comprises California annual grassland, some riparian vegetation, and a channelized floodplain whose vegetation has varied over the sampling years depending on seasonal flooding, fire, and management for flood control. It is basically a combination of annual and perennial floodplain vegetation with riparian and tule-marsh elements.