Plants modify their growth to fit their location. In low light, plants suppress branches (called tillers in grasses) in favor of growing tall to reach the light. Some of this branching flexibility originated in the Early Devonian (∼400 MYA) with the evolution of axillary branching. In axillary branching buds in leaf axils either remain dormant or grow out as branches. Similarly, growth suppression is important in the evolution of floral diversity. For example, unisexual flowers often form through suppression of specific organs during development. In maize, some genes that suppress branching also suppress floral organ development. However, whether these gene functions are conserved outside of maize, and how their regulation differs in different developmental contexts (branches vs. flowers) is unknown. In this work, I investigated three maize genes - RAMOSA3 (RA3), GRASSY TILLERS1 (GT1), and TEOSINTE BRANCHED1 (TB1) - which coordinate growth suppression across branches and flowers while integrating environmental cues. Notably, ra3 in a gt1 background leads to derepression of both tillers and pistils in flowers. To determine whether RA3’s growth suppression function is conserved across panicoid grasses, I analyzed the Setaria viridis svra3 mutant. While many described ra3 functions were conserved, I discovered new ra3 phenotypes in both maize and setaria. These findings underscore how examining a gene in species with distinct morphologies can illuminate aspects of its function. Next, I examined if the factors controlling tillering also affect pistil suppression. Shade signals activate expression of TB1, and TB1 turns on GT1 to suppress branch buds. To precisely measure pistil size and shape in maize, I developed a novel phenotyping method combining x-ray imaging with machine learning segmentation. Using this approach, I explored genetic interactions between tb1, gt1, and ra3 in pistil suppression. Mutant analyses suggest that TB1 does not act upstream of GT1 and RA3 in pistils. These results suggest that, although GT1 and RA3 act in both branch and pistil suppression, genetic regulation differs between these contexts. Overall, these findings show how careful phenotyping across species reveals gene functional complexity. My work also establishes a powerful phenotyping tool for future dissection of plant developmental genetics.