Body of Abstract: Nectar is a sugary substance produced by nectaries in flowers. Nectar is an energetic reward offered to visiting pollinators in exchange for the transfer of pollen between individuals. Nectaries are mostly considered sink tissues, and thus are reliant on carbon (C) from phloem-derived sugars to provide energy for growth and biosynthetic pathways. Prior to nectar secretion, nectaries in many species synthesize and accumulate starch. This starch disappears as nectar is produced, suggesting that nectary starch degradation provides C backbones for the synthesis and secretion of nectar sugars. However, no studies have shown direct evidence to support this notion. In this study, we sought to examine the role of nectary starch in nectar production in Arabidopsis thaliana. Towards this end, we generated nectary-specific mutants with alterations in nectary starch amount, including lines with critical starch synthesis gene APS1 silenced (pCRC::APS1_amiRNA), as well as lines containing a modified version of the E. coli APS1 gene (pCRC::glgC-TM_APS1), which prevents the normal in planta allosteric regulation of the APS1 enzyme. Nectary starch was absent from pCRC::APS1_amiRNA lines, whereas starch was over-produced in nectaries of the pCRC::glgC-TM_APS1 lines. Despite these opposite nectary starch phenotypes, both lines produced consistently less nectar than WT. Together, these data suggest that while the absence of nectary starch leads to a reduction in nectar sugar, unregulated nectary starch synthesis may compete for phloem-derived C precursors, pulling C away from the synthesis and secretion of nectar sugars. These findings help us to better understand how nectar is produced, which is an important first step towards engineering plants with enhanced nectar to optimize plant-pollinator relationships, reproductive success, and yield.