Plant communities within the river canyon can be divided into two broad categories: upland and riparian. The riparian zone is the green band of vegetation immediately adjacent to the river. It contains a wide diversity of leafy plant and shrub communities. Common riparian plants include white alder, willow and reed canarygrass. Common shrub species include spirea, mockorange, red-osier dogwood and wild rose. Upland vegetation is normally dominated by big sagebrush and bunchgrasses.
A limited amount of tree overstory exists in the form of widely scattered hackberry and western juniper trees. Abundant color is provided to the canyon walls in the spring by flowering plants such as the arrowleaf balsam root and a variety of lupine species. Hanging gardens can occasionally be found on steep canyon walls containing the hepatic monkey flower.