<p>Gibberellins (GAs) are crucial growth regulators governing diverse plant developmental processes. Arrowhead (<i>Sagittaria trifolia</i> L.) is a characteristic aquatic vegetable with a tall plant type and edible underground organs. To investigate the effects of GAs on the growth and yield formation of arrowhead, this study sprayed a type of gibberellin (GA₃) and a triazole-type gibberellin biosynthesis inhibitor (paclobutrazol, PP333) on the arrowhead plants, respectively, and then observed the phenotypic differences in the aboveground growth and the size of underground corms. Compared with the control group, GA₃ treatment significantly increased the plant height and reduced underground corm size, whereas the effect of PP333 treatment was the opposite. Anatomical observations revealed that the elongation of petiole epidermal cells and parenchyma cells after the application of GA₃ were the reason for the increased plant height of arrowhead plants. RT-qPCR analysis showed that the expression levels of <i>StKS1</i>, <i>StKS2</i>, <i>StKS3</i> and <i>StGA3ox</i> genes, related to endogenous GAs synthesis, in the petioles of arrowhead all exhibited significant differences under GA₃ and PP333 treatments. The current finding clarified the function of GAs in regulating the growth and yield formation of arrowhead, indicating that controlling the aboveground growth in arrowhead production is of great practical guiding significance for promoting yield formation.</p> Graphical Abstract <p></p>