Growers plan many of their horticultural activities around certain shoot phenological stages such as bloom and veraison. Timing of root growth in relation to these stages of the shoot is of interest in fertilization scheduling and understanding carbon allocation demands of the root system. With the recent use of minirhizotron root observation tubes, a much greater understanding of patterns of root growth has been made possible. In this paper some published work and present data from ongoing studies on timing of root production are reviewed. Studies discussed include ongoing work in grape vineyards in Fredonia, New York, USA (Vitis lambruscana), and Oakville, California, USA (V. vinifera), and in apple orchards (Malus × domestica) in Summerland, British Columbia, Canada. Root production mainly occurs in the summer, but the specific timing varies widely between bloom and harvest from year to year. Usually there is little root growth in the few weeks prior to harvest and when the vines are dormant. Cultural practices may affect root production, usually from a combination of changes in the soil environment (moisture, temperature) and changes in photosynthetic capacity.