Norditerpene alkaloid concentrations in tissues and floral rewards of larkspurs and impacts on pollinators

► Alkaloid concentrations differ among plant tissues and floral rewards. ► Alkaloid concentrations in floral parts were consistent with optimal defense theory. ► Some concentrations of norditerpene alkaloids influence the activity of bumble bees. ► Alkaloids in nectar are found at concentrations that have no effect on bee activity.