The eastern subspecies of the blue orchard bee, Osmia lignaria lignaria (Say), could be developed as an alternative pollinator for orchards in eastern North America. This bee begins to emerge from winter hibernation several weeks prior to apple blossom and remains active for several weeks afterwards. The objective of this study was to determine the pollen preference of these bees in their natural environment throughout the pollen collecting period and thus to better determine the flowering plants that could be used to encourage and increase bee populations near orchards without competing with fruit pollination. Over 70 potential pollen sources were identified. Approximately 400 pollen balls were sampled from several locations over two years. Digital photography was used to date nest completion and scanning electron microscopy was used to identify 300 pollen grains from each sample. Eastern red bud (Cercis canadensis L.) and box elder (Acer negundo L.) were the most important early food sources whereas later season sources included trees, shrubs, and herbs.