Global warming has the potential to affect plant growth, with changes in flowering phenology and nectar rewards that have subsequent effects on pollinating insects. Despite the importance of native vegetation for provisioning pollinating insects, few studies have evaluated the impacts of elevated temperatures on floral resource supply of native plant species, particularly in Australia. To examine the effects of warming on the flowering phenology and nectar production of 11 herbaceous plant species endemic to south-eastern Australia, we conducted a glasshouse experiment spanning the flowering season with two temperature treatments (ambient: 30°C [TA]; elevated: 34°C [TE]). We found that plant species differed widely in their responses to warming. Flowering phenology changed significantly under TE in three species and flower production was reduced in three species. While there was no significant treatment effect on the number of nectar-producing flowers and nectar sugar concentrations across species, individual flower nectar volume increased with warming in one species. Meanwhile, aboveground biomass production was reduced under TE in three species, and three species experienced a reduction in relative biomass allocation to reproductive, compared to vegetative, growth. These changes in reproductive resource allocation and floral phenology could impact floral resource availability, plant-pollinator interactions and pollination services in the future, notably for those critical resources supplied by winter flowering species, at times when overall floral resource availability in the landscape is low. This represents a risk for the long-term viability of vulnerable plant communities, including remnant native vegetation, that are already threatened due to land use change.