Key message <p>A scaling exponent numerically less than unity for the scaling of flower versus pedicel fresh mass was observed across seven Magnoliaceae species, indicating a disproportionate pedicel investment with increasing total flower mass.</p> Abstract <p>Although biomass allocation between vegetative organs (e.g., laminae and petioles) has been extensively studied, the quantitative patterns among floral organs, particularly between floral parts (i.e., the perianth, androecium, and gynoecium) and their supporting pedicels, remain largely unexplored. To address this gap, we analyzed flower versus pedicel biomass allocation patterns across seven Magnoliaceae species using a total of 2012 flowers. Flower fresh mass (FM_F) and pedicel fresh mass (FM_P: the internode between the uppermost annular stipular scar and perianth base) were measured. Reduced major axis regression signifies a statistically significant scaling relationship for FM_F versus FM_P (<i>r</i>² = 0.92). The scaling exponent for this relationship (α = 0.923 with its 95% confidence interval: 0.912 − 0.935) confirms the phenomenon called “diminishing returns” (i.e., increasing flower mass requires a disproportionately larger pedicel investment), which suggests prioritized biomass investing for mechanical or hydraulic support with increasing reproductive display. These findings provide additional insights into functional constraints in floral architecture. Future studies should expand taxonomic samplings to test the generality of FM_F versus FM_P scaling and compare functional investments in floral support structures (e.g., pedicels versus receptacles) across pollination syndromes to elucidate structural constraints in floral evolution.</p>