Xie et al. identify the genetic basis of tiller production and survival through a detailed quantitative trait locus (QTL) analysis in a bread wheat × spelt mapping population. In addition to genetic control, a low red:far red ratio (R:FR) is associated with early tillering cessation, few total shoots, high infertile shoot number and shoot abortion. They also determine the trade-offs between fertile shoot number and other yield components. These findings provide a deeper insight into the genetic and environmental determination of tillering dynamics and, in turn, yield potential in wheat.