Native bees are declining worldwide, but conserving or restoring their habitat requires a better understanding of bee-flower associations. High quality bee habitat includes flowers that provide pollen and nectar preferred by bees. However, little data exist about which plants are commonly used by bees in the Pacific Northwest, or whether bees prefer certain plant characteristics over others. We examined bee and plant communities in an Oregon riparian ecosystem. Our purpose was to describe bee-plant associations, determine which plants are most frequently visited by bees, identify plants that may be preferred by bees, and examine how a plant's native status, flower color, and floral morphology affect the types of bees visiting it. We found that many blooming plants received a diverse set of bee visitors, but some plants had a higher number and species richness of visiting bees than others. No plant species seemed limited to visitation by a small set of specialist bees. The number and type of visiting bees were not influenced by the plant's native status. However, flower morphology (but not color) significantly affected types of bees visiting plants. Bilaterally symmetrical and medium tubular flowers, with nectar and pollen typically more difficult to reach, were associated with larger bees with longer tongues, while smaller, easily accessible flowers attracted smaller bees with shorter tongues. Our results suggest that certain plants are particularly useful for supporting abundant and diverse bee communities, and increasing diversity in the morphology of blooming plants is a key factor to consider when restoring riparian areas for bee pollinators.