Using millions of records, we show that phenological and range shifts affect different attributes of the season: phenological shifts primarily alter the start, end, and duration of the season; range shifts alter co-flowering diversity at seasonal peaks and the network of overlapping flowering pairs

Shifts in phenology and species ranges are likely to have distinct and synergistic effects on community-level flowering patterns. However these processes have typically been studied in isolation largely due to data limitations.

The predominant role of plasticity was consistent among species distributed across climatic space and among ecoregions of the United States. However, the relative contributions of plasticity and adaptation varied markedly among species flowering at different times of the year

We found that, among species, sensitivity patterns were much more frequently consistent with plasticity than local adaptation, but both plasticity and adaptation jointly mediated clinal variation in phenology in many species

We used >1 million flowering specimens collected over 120yr representing 1,605 species to measure flowering sensitivity to T° over space and time, inferring the relative contributions of plasticity and adaptation to observed variation along T° gradients