In plants, root architecture is responsive to environmental changes. The plant hormones cytokinin, auxin and ethylene are known to regulate root growth: cytokinin signalling, acting via type-B ARR effectors, inhibits both proliferation and elongation of root cells, while auxin promotes cell division in the root apical meristem. Various mechanisms exist by which these signalling pathways interact to enable precise spatiotemporal control of root growth. On p. 3982, G. Eric Schaller and colleagues identify another level of cross-talk between these pathways in Arabidopsis. In a screen for regulators of cytokinin-mediated root growth control, they identify mutations in the gene encoding the auxin influx carrier AUX1 that enhance the cytokinin insensitivity of arr mutants. AUX1 seems to be specifically involved in cytokinin-mediated inhibition of root cell elongation but not proliferation. Since AUX1 is required for shootward transport of auxin via the lateral root cap, the authors propose that spatial modulation of this flux controls cell elongation in this region. Moreover, they identify a negative-feedback loop in the system – with ARRs inhibiting AUX1 expression, and AUX1 promoting ARR10 expression – that might set up oscillating patterns of hormone flux and gene expression in the root.