Strigolactones (SLs) and their derivatives are plant hormones that have recently been identified as regulating root development. Sun et al. study adventious roots (ARs) in SL-deficient (d10) and SL-insensitive (d3) mutants of rice, Oryza sativa, and find that d mutants exhibit reduced AR production compared to the wild type. Application of GR24 (a synthetic SL analogue) increases the number of ARs and average AR number per tiller in d10, but not in d3. The results suggest that AR formation is positively regulated by SLs via the D3 response pathway. A positive effect of application of exogenous auxin and the opposite effect of application of NPA (a polar auxin transport inhibitor) on AR number in wild type plants also suggests the importance of auxin for AR formation, but the interaction between auxin and SLs is complex.