Commercial bioinoculants for horticultural use that contain arbuscular mycorrhizal fungi (AMF) offer a potential alternative to conventional grapevine (Vitis) management strategies that are dependent on the use of agrochemicals. This field study assessed whether inoculation with AMF increased root length colonization, vine growth, leaf blade nutrient concentration, bud cold hardiness, and vine water status under a range of application methods, soils, and rootstocks. AMF inoculation increased root mycorrhizal colonization of ‘Pinot Noir’ (Vitis vinifera) grafted onto rootstocks ‘Courderc 3309C’ (Vitis riparia × Vitis rupestris) and ‘Millardet et de Grasset 101-14’ (Vitis riparia × Vitis rupestris). However, inoculation did not increase root mycorrhizal colonization of ‘Riesling’ (Vitis vinifera) grafted onto rootstocks ‘Courderc 3309C’ (Vitis riparia × Vitis rupestris) and Selection Oppenheim four (Vitis berlandieri × V. riparia), ‘Regent’ (Vitis vinifera) grafted onto rootstock ‘Millardet et de Grasset 101-14’ (Vitis riparia × Vitis rupestris), and ‘Verdejo’ (Vitis vinifera) grafted onto rootstock ‘Courderc 3309C’ (Vitis riparia × Vitis rupestris). Findings do not support the use of commercial bioinoculants for increased grapevine root length colonization; however, these results may be affected by competition between indigenous and commercial AM fungi, environmental and soil conditions, scion-rootstock interactions, and bioinoculant quality.