With heavy water use and other inputs, residential lawns and traditional yard features result in resource consumption, pollution, and changes in biodiversity. Several studies have examined the driving forces behind landscaping practices, but few have examined how social institutions affect residents’ decisions. We fill this gap by asking: how do formal and informal rules influence yard management, and how do these institutions interact in particular neighborhoods? Our interview-based case study is situated in Phoenix, Arizona, where outdoor irrigation constitutes a large portion of water demand. Overall, informal norms and customs at varying scales more strongly influence landscaping decisions than codified rules in our study. While residents appreciate diverse yard types, dominant norms involve pervasive expectations for neatness as well as varied plant choices grounded in historic traditions and personal experiences. Legacy effects and paradoxes concerning water conservation and urban homogenization also emerged from this research. Although insightful, these findings should be tested in diverse biomes to see how transferable they are across different contexts.