In an era of widespread pollinator declines, bumble bees (Apidae: Bombus) are a frequent research focus in invertebrate ecology and conservation due to their contributions to ecosystem function. However, we often still lack fine-grained floral visitation data, which can hinder management and restoration efforts for both bees and the plants they visit. Here, we present results of a multi-year bumble bee population and floral resource monitoring effort in mountain meadows of the Sierra Nevada, California, USA. We quantify floral resource use relative to availability and identify putatively important plant species for over a dozen Bombus species to assist with ongoing restoration of ecologically-important meadow habitats in the Sierra. Using an occupancy-modeling framework, we also find that bumble bee populations cyclically alternate years of high and low abundance across the study period and examine possible drivers of these fluctuations and their phenology. Our relative lack of Bombus occidentalis observations, a species of conservation concern, provides additional context for its precipitous decline across North America.