Plant development is subject to hormonal growth control and adapts to environmental cues such as light or stress. Recently, significant progress has been made in elucidating hormone synthesis, signalling and degradation pathways, and in resolving spatial and temporal aspects of hormone responses. Here we review how hormones control maintenance of stem cell systems, influence developmental transitions of stem cell daughters and define developmental compartments in Arabidopsis thaliana. We also discuss how environmental cues change plant growth by modulating hormone levels and response. Future analysis of hormone crosstalk and of hormone action at both single cell and organ levels will substantially improve our understanding of how plant development adapts to changes in intrinsic and environmental conditions.