Proper tree spacing is a key to maximizing the production potential of an apple orchard. Along with cultivar, rootstock, and management system, soil conditions affect tree size and thus tree spacing making it necessary to evaluate rootstock performance under a variety of different soil conditions. The loess soils of western Iowa are unique, and little is known about their influence on apple tree growth, particularly on dwarfing rootstocks. This study was established to evaluate the performance of apple cultivars on rootstocks ranging from full dwarfing to standard-size to better ascertain optimum spacing for apple trees planted on loess soils.