Display omitted •Current evidence for iron-oxo reactive intermediates is reviewed.•In crystallo intermediates detected in a native extradiol dioxygenase reaction.•Carotenoid cleavage dioxygenases catalyse strigolactone biosynthesis.•Identification of plant cysteine oxidases involved in the plant hypoxic response.•Applications of enzyme manipulation to plant biology and agriculture are discussed. Non-heme iron-dependent oxygenases catalyse the incorporation of O2 into a wide range of biological molecules and use diverse strategies to activate their substrates. Recent kinetic studies, including in crystallo, have provided experimental support for some of the intermediates used by different subclasses of this enzyme family. Plant non-heme iron-dependent oxygenases have diverse and important biological roles, including in growth signalling, stress responses and secondary metabolism. Recently identified roles include in strigolactone biosynthesis, O-demethylation in morphine biosynthesis and regulating the stability of hypoxia-responsive transcription factors. We discuss current structural and mechanistic understanding of plant non-heme iron oxygenases, and how their chemical/genetic manipulation could have agricultural benefit, for example, for improved yield, stress tolerance or herbicide development.