Pollen morphology is species-specific and its identification can inform many different research objectives, including those focused on understanding pollinator niche breadth, pollen transfer dynamics, and factors driving plant community composition. Community-wide characterization of pollen can thus accelerate research on plant-pollinator interactions on both contemporary and historical time frames. Here we present descriptions, a dichotomous key, and reference set of light microscopy images of pollen from 70 species in 28 families of co-flowering plants growing in and around serpentine seeps at the McLaughlin Natural Reserve in Lake County, CA. This represents a reference and a tool for the study of species interactions in this unique biodiversity hotspot.