Flowers are essential for reproduction for most flowering plants (angiosperms). By ensuring pollen production and ovule fertilization, flowers maximize outcrossing and enable fruit and seed production, thus directly impacting plant fitness. Despite the importance of flowers to plant function and evolution, remarkably little is known about how and when they become vulnerable to water stress in natural environments. This knowledge is especially urgent because increasingly frequent extreme drought events could threaten flower function and, by extension, reproduction.  Remarkably few studies have measured the physiological tolerances of flowers, and their sample designs have almost completely ignored the ecological and environmental contexts in which flowers live. Here, I aimed to characterize morphological and physiological traits linked to flower and leaf water balance and construction costs. I measured flower and leaf mass per area (FMA and LMA, in g m-2), flower and leaf water content (%), petal and leaf thickness (mm), flower and leaf area (cm2), and residual transpiration (gmin, mmol m-2 s-1) for 34 species belonging to 16 plant families. The ranges of trait variability were in the same order of magnitude for both flowers and leaves, with flowers and leaves being of similar size (7.67 ± 7.02 cm2 and 8.05 ± 9.82 cm2, respectively). Flowers have greater water costs but lower dry mass costs than their conspecific leaves despite being thinner than leaves. This is shown by the higher proportion of water content in flowers and the lower values of flower mass per area compared to the leaf mass per area. The mean water content in flowers was 81.82% (SD = 5.01) while in leaves, it was 61.22% (SD = 5.01), and the mean thickness of flowers was 0.14 mm (SD = 0.19) while in leaves, it was 0.55 mm (SD = 0.40). As expected, the biomass per unit area was greater in leaves than in flowers, 170.48 (SD = 51.34) and 55.44 g m-2 (SD = 68.49), respectively. Thus, contrary to leaves that have multiple strategies to store water (e.g., low values of LMA and thickness or high values of LMA and thickness), flowers tend to exhibit just high values of water content that trades-off for low tissue quality (i.e., low biomass per area, FMA). This structural pattern should reduce the production costs of flowers and is predicted from their relatively short lifespan. Lastly, the gmin values were slightly greater in leaves (18.30 mmol m-2 s-1, SD = 13.68) than in flowers (14.51 mmol m-2 s-1, SD = 10.67), suggesting that flowers are better able to restrict water loss during droughts. This work reveals previously overlooked factors affecting plant distributions and their sensitivity to climate.